- 02 Dec, 2022 11 commits
-
-
Sean Christopherson authored
Use the dedicated non-atomic helpers for {clear,set}_bit() and their test variants, i.e. the double-underscore versions. Depsite being defined in atomic.h, and despite the kernel versions being atomic in the kernel, tools' {clear,set}_bit() helpers aren't actually atomic. Move to the double-underscore versions so that the versions that are expected to be atomic (for kernel developers) can be made atomic without affecting users that don't want atomic operations. No functional change intended. Signed-off-by:Sean Christopherson <seanjc@google.com> Acked-by:
Namhyung Kim <namhyung@kernel.org> Message-Id: <20221119013450.2643007-6-seanjc@google.com> Signed-off-by:
Paolo Bonzini <pbonzini@redhat.com>
-
Sean Christopherson authored
Take @bit as an unsigned long instead of a signed int in clear_bit() and set_bit() so that they match the double-underscore versions, __clear_bit() and __set_bit(). This will allow converting users that really don't want atomic operations to the double-underscores without introducing a functional change, which will in turn allow making {clear,set}_bit() atomic (as advertised). Practically speaking, this _should_ have no functional impact. KVM's selftests usage is either hardcoded (Hyper-V tests) or is artificially limited (arch_timer test and dirty_log test). In KVM, dirty_log test is the only mildly interesting case as it's use indirectly restricted to unsigned 32-bit values, but in theory it could generate a negative value when cast to a signed int. But in that case, taking an "unsigned long" is actually a bug fix. Perf's usage is more difficult to audit, but any code that is affected by the switch is likely already broken. perf_header__{set,clear}_feat() and perf_file_header__read() effectively use only hardcoded enums with small, positive values, atom_new() passes an unsigned long, but its value is capped at 128 via NR_ATOM_PER_PAGE, etc... The only real potential for breakage is in the perf flows that take a "cpu", but it's unlikely perf is subtly relying on a negative index into bitmaps, e.g. "cpu" can be "-1", but only as "not valid" placeholder. Note, tools/testing/nvdimm/ makes heavy use of set_bit(), but that code builds into a kernel module of sorts, i.e. pulls in all of the kernel's header and so is getting the kernel's atomic set_bit(). The NVDIMM test usage of atomics is likely unnecessary, e.g. ndtest_dimm_register() sets bits in a local variable, but that's neither here nor there as far as this change is concerned. Signed-off-by: -
Sean Christopherson authored
Add a new ucall hook, GUEST_UCALL_NONE(), to allow tests to make ucalls without allocating a ucall struct, and use it to enable single-step in ARM's debug-exceptions test. Like the disable single-step path, the enabling path also needs to ensure that no exclusive access sequences are attempted after enabling single-step, as the exclusive monitor is cleared on ERET from the debug exception taken to EL2. The test currently "works" because clear_bit() isn't actually an atomic operation... yet. Signed-off-by:
-
Yuan ZhaoXiong authored
When a VM reboots itself, the reset process will result in an ioctl(KVM_SET_LAPIC, ...) to disable x2APIC mode and set the xAPIC id of the vCPU to its default value, which is the vCPU id. That will be handled in KVM as follows: kvm_vcpu_ioctl_set_lapic kvm_apic_set_state kvm_lapic_set_base => disable X2APIC mode kvm_apic_state_fixup kvm_lapic_xapic_id_updated kvm_xapic_id(apic) != apic->vcpu->vcpu_id kvm_set_apicv_inhibit(APICV_INHIBIT_REASON_APIC_ID_MODIFIED) memcpy(vcpu->arch.apic->regs, s->regs, sizeof(*s)) => update APIC_ID When kvm_apic_set_state invokes kvm_lapic_set_base to disable x2APIC mode, the old 32-bit x2APIC id is still present rather than the 8-bit xAPIC id. kvm_lapic_xapic_id_updated will set the APICV_INHIBIT_REASON_APIC_ID_MODIFIED bit and disable APICv/x2AVIC. Instead, kvm_lapic_xapic_id_updated must be called after APIC_ID is changed. In fact, this fixes another small issue in the code in that potential changes to a vCPU's xAPIC ID need not be tracked for KVM_GET_LAPIC. Fixes: 3743c2f0 ("KVM: x86: inhibit APICv/AVIC on changes to APIC ID or APIC base") Signed-off-by:Yuan ZhaoXiong <yuanzhaoxiong@baidu.com> Message-Id: <1669984574-32692-1-git-send-email-yuanzhaoxiong@baidu.com> Cc: stable@vger.kernel.org Reported-by:
Alejandro Jimenez <alejandro.j.jimenez@oracle.com> Signed-off-by:
-
Sean Christopherson authored
Remove a comment about KVM_REQ_UNHALT being set by kvm_vcpu_check_block() that was missed when KVM_REQ_UNHALT was dropped. Fixes: c59fb127 ("KVM: remove KVM_REQ_UNHALT") Signed-off-by:
-
https://github.com/kvm-x86/linuxPaolo Bonzini authored
Misc KVM x86 fixes and cleanups for 6.2: - One-off fixes for various emulation flows (SGX, VMXON, NRIPS=0). - Reinstate IBPB on emulated VM-Exit that was incorrectly dropped a few years back when eliminating unnecessary barriers when switching between vmcs01 and vmcs02. - Clean up the MSR filter docs. - Clean up vmread_error_trampoline() to make it more obvious that params must be passed on the stack, even for x86-64. - Let userspace set all supported bits in MSR_IA32_FEAT_CTL irrespective of the current guest CPUID. - Fudge around a race with TSC refinement that results in KVM incorrectly thinking a guest needs TSC scaling when running on a CPU with a constant TSC, but no hardware-enumerated TSC frequency.
-
https://github.com/kvm-x86/linuxPaolo Bonzini authored
KVM selftests fixes for 6.2 - Fix an inverted check in the access tracking perf test, and restore support for asserting that there aren't too many idle pages when running on bare metal. - Fix an ordering issue in the AMX test introduced by recent conversions to use kvm_cpu_has(), and harden the code to guard against similar bugs in the future. Anything that tiggers caching of KVM's supported CPUID, kvm_cpu_has() in this case, effectively hides opt-in XSAVE features if the caching occurs before the test opts in via prctl(). - Fix build errors that occur in certain setups (unsure exactly what is unique about the problematic setup) due to glibc overriding static_assert() to a variant that requires a custom message.
-
Javier Martinez Canillas authored
The ioctls are missing an architecture property that is present in others. Suggested-by:
Sergio Lopez Pascual <slp@redhat.com> Signed-off-by:
Javier Martinez Canillas <javierm@redhat.com> Message-Id: <20221202105011.185147-5-javierm@redhat.com> Signed-off-by:
-
Javier Martinez Canillas authored
There are still references to the removed kvm_memory_region data structure but the doc and comments should mention struct kvm_userspace_memory_region instead, since that is what's used by the ioctl that replaced the old one and this data structure support the same set of flags. Signed-off-by:
-
Javier Martinez Canillas authored
The documentation says that the ioctl has been deprecated, but it has been actually removed and the remaining references are just left overs. Suggested-by:
-
Javier Martinez Canillas authored
The documentation says that the ioctl has been deprecated, but it has been actually removed and the remaining references are just left overs. Suggested-by:
-
- 01 Dec, 2022 23 commits
-
-
Sean Christopherson authored
Define and use kvm_static_assert() in the common KVM selftests headers to provide deterministic behavior, and to allow creating static asserts without dummy messages. The kernel's static_assert() makes the message param optional, and on the surface, tools/include/linux/build_bug.h appears to follow suit. However, glibc may override static_assert() and redefine it as a direct alias of _Static_assert(), which makes the message parameter mandatory. This leads to non-deterministic behavior as KVM selftests code that utilizes static_assert() without a custom message may or not compile depending on the order of includes. E.g. recently added asserts in x86_64/processor.h fail on some systems with errors like In file included from lib/memstress.c:11:0: include/x86_64/processor.h: In function ‘this_cpu_has_p’: include/x86_64/processor.h:193:34: error: expected ‘,’ before ‘)’ token static_assert(low_bit < high_bit); \ ^ due to _Static_assert() expecting a comma before a message. The "message optional" version of static_assert() uses macro magic to strip away the comma when presented with empty an __VA_ARGS__ #ifndef static_assert #define static_assert(expr, ...) __static_assert(expr, ##__VA_ARGS__, #expr) #define __static_assert(expr, msg, ...) _Static_assert(expr, msg) #endif // static_assert and effectively generates "_Static_assert(expr, #expr)". The incompatible version of static_assert() gets defined by this snippet in /usr/include/assert.h: #if defined __USE_ISOC11 && !defined __cplusplus # undef static_assert # define static_assert _Static_assert #endif which yields "_Static_assert(expr)" and thus fails as above. KVM selftests don't actually care about using C11, but __USE_ISOC11 gets defined because of _GNU_SOURCE, which many tests do #define. _GNU_SOURCE triggers a massive pile of defines in /usr/include/features.h, including _ISOC11_SOURCE: /* If _GNU_SOURCE was defined by the user, turn on all the other features. */ #ifdef _GNU_SOURCE # undef _ISOC95_SOURCE # define _ISOC95_SOURCE 1 # undef _ISOC99_SOURCE # define _ISOC99_SOURCE 1 # undef _ISOC11_SOURCE # define _ISOC11_SOURCE 1 # undef _POSIX_SOURCE # define _POSIX_SOURCE 1 # undef _POSIX_C_SOURCE # define _POSIX_C_SOURCE 200809L # undef _XOPEN_SOURCE # define _XOPEN_SOURCE 700 # undef _XOPEN_SOURCE_EXTENDED # define _XOPEN_SOURCE_EXTENDED 1 # undef _LARGEFILE64_SOURCE # define _LARGEFILE64_SOURCE 1 # undef _DEFAULT_SOURCE # define _DEFAULT_SOURCE 1 # undef _ATFILE_SOURCE # define _ATFILE_SOURCE 1 #endif which further down in /usr/include/features.h leads to: /* This is to enable the ISO C11 extension. */ #if (defined _ISOC11_SOURCE \ || (defined __STDC_VERSION__ && __STDC_VERSION__ >= 201112L)) # define __USE_ISOC11 1 #endif To make matters worse, /usr/include/assert.h doesn't guard against multiple inclusion by turning itself into a nop, but instead #undefs a few macros and continues on. As a result, it's all but impossible to ensure the "message optional" version of static_assert() will actually be used, e.g. explicitly including assert.h and #undef'ing static_assert() doesn't work as a later inclusion of assert.h will again redefine its version. #ifdef _ASSERT_H # undef _ASSERT_H # undef assert # undef __ASSERT_VOID_CAST # ifdef __USE_GNU # undef assert_perror # endif #endif /* assert.h */ #define _ASSERT_H 1 #include <features.h> Fixes: fcba483e ("KVM: selftests: Sanity check input to ioctls() at build time") Fixes: ee379553 ("KVM: selftests: Refactor X86_FEATURE_* framework to prep for X86_PROPERTY_*") Fixes: 53a7dc0f ("KVM: selftests: Add X86_PROPERTY_* framework to retrieve CPUID values") Signed-off-by: -
Sean Christopherson authored
Move the AMX test's kvm_cpu_has() checks before creating the VM+vCPU, there are no dependencies between the two operations. Opportunistically add a comment to call out that enabling off-by-default XSAVE-managed features must be done before KVM_GET_SUPPORTED_CPUID is cached. Signed-off-by:
-
Sean Christopherson authored
Disallow using kvm_get_supported_cpuid() and thus caching KVM's supported CPUID info before enabling XSAVE-managed features that are off-by-default and must be enabled by ARCH_REQ_XCOMP_GUEST_PERM. Caching the supported CPUID before all XSAVE features are enabled can result in false negatives due to testing features that were cached before they were enabled. Signed-off-by:
-
Sean Christopherson authored
Move __vm_xsave_require_permission() below the CPUID helpers so that a future change can reference the cached result of KVM_GET_SUPPORTED_CPUID while keeping the definition of the variable close to its intended user, kvm_get_supported_cpuid(). No functional change intended. Signed-off-by:
-
Lei Wang authored
Move the kvm_cpu_has() check on X86_FEATURE_XFD out of the helper to enable off-by-default XSAVE-managed features and into the one test that currenty requires XFD (XFeature Disable) support. kvm_cpu_has() uses kvm_get_supported_cpuid() and thus caches KVM_GET_SUPPORTED_CPUID, and so using kvm_cpu_has() before ARCH_REQ_XCOMP_GUEST_PERM effectively results in the test caching stale values, e.g. subsequent checks on AMX_TILE will get false negatives. Although off-by-default features are nonsensical without XFD, checking for XFD virtualization prior to enabling such features isn't strictly required. Signed-off-by:
Lei Wang <lei4.wang@intel.com> Fixes: 7fbb653e ("KVM: selftests: Check KVM's supported CPUID, not host CPUID, for XFD") Link: https://lore.kernel.org/r/20221125023839.315207-1-lei4.wang@intel.com [sean: add Fixes, reword changelog] Signed-off-by:
-
Sean Christopherson authored
Restore the assert (on x86-64) that <10% of pages are still idle when NOT running as a nested VM in the access tracking test. The original assert was converted to a "warning" to avoid false failures when running the test in a VM, but the non-nested case does not suffer from the same "infinite TLB size" issue. Using the HYPERVISOR flag isn't infallible as VMMs aren't strictly required to enumerate the "feature" in CPUID, but practically speaking anyone that is running KVM selftests in VMs is going to be using a VMM and hypervisor that sets the HYPERVISOR flag. Cc: David Matlack <dmatlack@google.com> Reviewed-by:
Emanuele Giuseppe Esposito <eesposit@redhat.com> Signed-off-by:
-
Sean Christopherson authored
Warn if the number of idle pages is greater than or equal to 10% of the total number of pages, not if the percentage of idle pages is less than 10%. The original code asserted that less than 10% of pages were still idle, but the check got inverted when the assert was converted to a warning. Opportunistically clean up the warning; selftests are 64-bit only, there is no need to use "%PRIu64" instead of "%lu". Fixes: 6336a810 ("KVM: selftests: replace assertion with warning in access_tracking_perf_test") Reviewed-by:
-
Anton Romanov authored
Don't snapshot tsc_khz into per-cpu cpu_tsc_khz if the host TSC is constant, in which case the actual TSC frequency will never change and thus capturing TSC during initialization is unnecessary, KVM can simply use tsc_khz. This value is snapshotted from kvm_timer_init->kvmclock_cpu_online->tsc_khz_changed(NULL) On CPUs with constant TSC, but not a hardware-specified TSC frequency, snapshotting cpu_tsc_khz and using that to set a VM's target TSC frequency can lead to VM to think its TSC frequency is not what it actually is if refining the TSC completes after KVM snapshots tsc_khz. The actual frequency never changes, only the kernel's calculation of what that frequency is changes. Ideally, KVM would not be able to race with TSC refinement, or would have a hook into tsc_refine_calibration_work() to get an alert when refinement is complete. Avoiding the race altogether isn't practical as refinement takes a relative eternity; it's deliberately put on a work queue outside of the normal boot sequence to avoid unnecessarily delaying boot. Adding a hook is doable, but somewhat gross due to KVM's ability to be built as a module. And if the TSC is constant, which is likely the case for every VMX/SVM-capable CPU produced in the last decade, the race can be hit if and only if userspace is able to create a VM before TSC refinement completes; refinement is slow, but not that slow. For now, punt on a proper fix, as not taking a snapshot can help some uses cases and not taking a snapshot is arguably correct irrespective of the race with refinement. Signed-off-by:
Anton Romanov <romanton@google.com> Reviewed-by:
-
Sean Christopherson authored
Verify the KVM allows userspace to set all supported bits in the IA32_FEATURE_CONTROL MSR irrespective of the current guest CPUID, and that all unsupported bits are rejected. Throw the testcase into vmx_msrs_test even though it's not technically a VMX MSR; it's close enough, and the most frequently feature controlled by the MSR is VMX. Signed-off-by:
-
Sean Christopherson authored
Move the check on IA32_FEATURE_CONTROL being locked, i.e. read-only from the guest, into the helper to check the overall validity of the incoming value. Opportunistically rename the helper to make it clear that it returns a bool. No functional change intended. Signed-off-by:
-
Sean Christopherson authored
Allow userspace to set all supported bits in MSR IA32_FEATURE_CONTROL irrespective of the guest CPUID model, e.g. via KVM_SET_MSRS. KVM's ABI is that userspace is allowed to set MSRs before CPUID, i.e. can set MSRs to values that would fault according to the guest CPUID model. Signed-off-by:
-
Sean Christopherson authored
Declare vmread_error_trampoline() as an opaque symbol so that it cannot be called from C code, at least not without some serious fudging. The trampoline always passes parameters on the stack so that the inline VMREAD sequence doesn't need to clobber registers. regparm(0) was originally added to document the stack behavior, but it ended up being confusing because regparm(0) is a nop for 64-bit targets. Opportunustically wrap the trampoline and its declaration in #ifdeffery to make it even harder to invoke incorrectly, to document why it exists, and so that it's not left behind if/when CONFIG_CC_HAS_ASM_GOTO_OUTPUT is true for all supported toolchains. No functional change intended. Cc: Uros Bizjak <ubizjak@gmail.com> Signed-off-by:
-
Sean Christopherson authored
Reword the comments that (attempt to) document nVMX's overrides of the CR0/4 read shadows for L2 after calling vmx_set_cr0/4(). The important behavior that needs to be documented is that KVM needs to override the shadows to account for L1's masks even though the shadows are set by the common helpers (and that setting the shadows first would result in the correct shadows being clobbered). Signed-off-by:
Jim Mattson <jmattson@google.com> Link: https://lore.kernel.org/r/20220831000721.4066617-1-seanjc@google.com
-
Sean Christopherson authored
Clean up the KVM_CAP_X86_USER_SPACE_MSR documentation to eliminate misleading and/or inconsistent verbiage, and to actually document what accesses are intercepted by which flags. - s/will/may since not all #GPs are guaranteed to be intercepted - s/deflect/intercept to align with common KVM terminology - s/user space/userspace to align with the majority of KVM docs - Avoid using "trap" terminology, as KVM exits to userspace _before_ stepping, i.e. doesn't exhibit trap-like behavior - Actually document the flags Signed-off-by: -
Sean Christopherson authored
Reword the MSR filtering documentatiion to more precisely define the behavior of filtering using common virtualization terminology. - Explicitly document KVM's behavior when an MSR is denied - s/handled/allowed as there is no guarantee KVM will "handle" the MSR access - Drop the "fall back" terminology, which incorrectly suggests that there is existing KVM behavior to fall back to - Fix an off-by-one error in the range (the end is exclusive) - Call out the interaction between MSR filtering and KVM_CAP_X86_USER_SPACE_MSR's KVM_MSR_EXIT_REASON_FILTER - Delete the redundant paragraph on what '0' and '1' in the bitmap means, it's covered by the sections on KVM_MSR_FILTER_{READ,WRITE} - Delete the clause on x2APIC MSR behavior depending on APIC base, this is covered by stating that KVM follows architectural behavior when emulating/virtualizing MSR accesses Reported-by:Aaron Lewis <aaronlewis@google.com> Signed-off-by:
-
Sean Christopherson authored
Delete the paragraph that describes the behavior when both KVM_MSR_FILTER_READ | KVM_MSR_FILTER_WRITE are set for a range. There is nothing special about KVM's handling of this combination, whereas explicitly documenting the combination suggests that there is some magic behavior the user needs to be aware of. Signed-off-by:
-
Jim Mattson authored
According to Intel's document on Indirect Branch Restricted Speculation, "Enabling IBRS does not prevent software from controlling the predicted targets of indirect branches of unrelated software executed later at the same predictor mode (for example, between two different user applications, or two different virtual machines). Such isolation can be ensured through use of the Indirect Branch Predictor Barrier (IBPB) command." This applies to both basic and enhanced IBRS. Since L1 and L2 VMs share hardware predictor modes (guest-user and guest-kernel), hardware IBRS is not sufficient to virtualize IBRS. (The way that basic IBRS is implemented on pre-eIBRS parts, hardware IBRS is actually sufficient in practice, even though it isn't sufficient architecturally.) For virtual CPUs that support IBRS, add an indirect branch prediction barrier on emulated VM-exit, to ensure that the predicted targets of indirect branches executed in L1 cannot be controlled by software that was executed in L2. Since we typically don't intercept guest writes to IA32_SPEC_CTRL, perform the IBPB at emulated VM-exit regardless of the current IA32_SPEC_CTRL.IBRS value, even though the IBPB could technically be deferred until L1 sets IA32_SPEC_CTRL.IBRS, if IA32_SPEC_CTRL.IBRS is clear at emulated VM-exit. This is CVE-2022-2196. Fixes: 5c911bef ("KVM: nVMX: Skip IBPB when switching between vmcs01 and vmcs02") Cc: Sean Christopherson <seanjc@google.com> Signed-off-by:
-
Jim Mattson authored
At this point in time, most guests (in the default, out-of-the-box configuration) are likely to use IA32_SPEC_CTRL. Therefore, drop the compiler hint that it is unlikely for KVM to be intercepting WRMSR of IA32_SPEC_CTRL. Signed-off-by:
-
Sean Christopherson authored
Inject #GP for if VMXON is attempting with a CR0/CR4 that fails the generic "is CRx valid" check, but passes the CR4.VMXE check, and do the generic checks _after_ handling the post-VMXON VM-Fail. The CR4.VMXE check, and all other #UD cases, are special pre-conditions that are enforced prior to pivoting on the current VMX mode, i.e. occur before interception if VMXON is attempted in VMX non-root mode. All other CR0/CR4 checks generate #GP and effectively have lower priority than the post-VMXON check. Per the SDM: IF (register operand) or (CR0.PE = 0) or (CR4.VMXE = 0) or ... THEN #UD; ELSIF not in VMX operation THEN IF (CPL > 0) or (in A20M mode) or (the values of CR0 and CR4 are not supported in VMX operation) THEN #GP(0); ELSIF in VMX non-root operation THEN VMexit; ELSIF CPL > 0 THEN #GP(0); ELSE VMfail("VMXON executed in VMX root operation"); FI; which, if re-written without ELSIF, yields: IF (register operand) or (CR0.PE = 0) or (CR4.VMXE = 0) or ... THEN #UD IF in VMX non-root operation THEN VMexit; IF CPL > 0 THEN #GP(0) IF in VMX operation THEN VMfail("VMXON executed in VMX root operation"); IF (in A20M mode) or (the values of CR0 and CR4 are not supported in VMX operation) THEN #GP(0); Note, KVM unconditionally forwards VMXON VM-Exits that occur in L2 to L1, i.e. there is no need to check the vCPU is not in VMX non-root mode. Add a comment to explain why unconditionally forwarding such exits is functionally correct. Reported-by:Eric Li <ercli@ucdavis.edu> Fixes: c7d855c2 ("KVM: nVMX: Inject #UD if VMXON is attempted with incompatible CR0/CR4") Cc: stable@vger.kernel.org Signed-off-by:
-
Zhao Liu authored
The use of kmap_atomic() is being deprecated in favor of kmap_local_page()[1]. The main difference between atomic and local mappings is that local mappings don't disable page faults or preemption. There're 2 reasons we can use kmap_local_page() here: 1. SEV is 64-bit only and kmap_local_page() doesn't disable migration in this case, but here the function clflush_cache_range() uses CLFLUSHOPT instruction to flush, and on x86 CLFLUSHOPT is not CPU-local and flushes the page out of the entire cache hierarchy on all CPUs (APM volume 3, chapter 3, CLFLUSHOPT). So there's no need to disable preemption to ensure CPU-local. 2. clflush_cache_range() doesn't need to disable pagefault and the mapping is still valid even if sleeps. This is also true for sched out/in when preempted. In addition, though kmap_local_page() is a thin wrapper around page_address() on 64-bit, kmap_local_page() should still be used here in preference to page_address() since page_address() isn't suitable to be used in a generic function (like sev_clflush_pages()) where the page passed in is not easy to determine the source of allocation. Keeping the kmap* API in place means it can be used for things other than highmem mappings[2]. Therefore, sev_clflush_pages() is a function that should use kmap_local_page() in place of kmap_atomic(). Convert the calls of kmap_atomic() / kunmap_atomic() to kmap_local_page() / kunmap_local(). [1]: https://lore.kernel.org/all/20220813220034.806698-1-ira.weiny@intel.com [2]: https://lore.kernel.org/lkml/5d667258-b58b-3d28-3609-e7914c99b31b@intel.com/Suggested-by:
Dave Hansen <dave.hansen@intel.com> Suggested-by:
Ira Weiny <ira.weiny@intel.com> Suggested-by:
Fabio M. De Francesco <fmdefrancesco@gmail.com> Signed-off-by:
Zhao Liu <zhao1.liu@intel.com> Reviewed-by:
-
Sean Christopherson authored
Skip the WRMSR fastpath in SVM's VM-Exit handler if the next RIP isn't valid, e.g. because KVM is running with nrips=false. SVM must decode and emulate to skip the WRMSR if the CPU doesn't provide the next RIP. Getting the instruction bytes to decode the WRMSR requires reading guest memory, which in turn means dereferencing memslots, and that isn't safe because KVM doesn't hold SRCU when the fastpath runs. Don't bother trying to enable the fastpath for this case, e.g. by doing only the WRMSR and leaving the "skip" until later. NRIPS is supported on all modern CPUs (KVM has considered making it mandatory), and the next RIP will be valid the vast, vast majority of the time. ============================= WARNING: suspicious RCU usage 6.0.0-smp--4e557fcd3d80-skip #13 Tainted: G O ----------------------------- include/linux/kvm_host.h:954 suspicious rcu_dereference_check() usage! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 1 lock held by stable/206475: #0: ffff9d9dfebcc0f0 (&vcpu->mutex){+.+.}-{3:3}, at: kvm_vcpu_ioctl+0x8b/0x620 [kvm] stack backtrace: CPU: 152 PID: 206475 Comm: stable Tainted: G O 6.0.0-smp--4e557fcd3d80-skip #13 Hardware name: Google, Inc. Arcadia_IT_80/Arcadia_IT_80, BIOS 10.48.0 01/27/2022 Call Trace: <TASK> dump_stack_lvl+0x69/0xaa dump_stack+0x10/0x12 lockdep_rcu_suspicious+0x11e/0x130 kvm_vcpu_gfn_to_memslot+0x155/0x190 [kvm] kvm_vcpu_gfn_to_hva_prot+0x18/0x80 [kvm] paging64_walk_addr_generic+0x183/0x450 [kvm] paging64_gva_to_gpa+0x63/0xd0 [kvm] kvm_fetch_guest_virt+0x53/0xc0 [kvm] __do_insn_fetch_bytes+0x18b/0x1c0 [kvm] x86_decode_insn+0xf0/0xef0 [kvm] x86_emulate_instruction+0xba/0x790 [kvm] kvm_emulate_instruction+0x17/0x20 [kvm] __svm_skip_emulated_instruction+0x85/0x100 [kvm_amd] svm_skip_emulated_instruction+0x13/0x20 [kvm_amd] handle_fastpath_set_msr_irqoff+0xae/0x180 [kvm] svm_vcpu_run+0x4b8/0x5a0 [kvm_amd] vcpu_enter_guest+0x16ca/0x22f0 [kvm] kvm_arch_vcpu_ioctl_run+0x39d/0x900 [kvm] kvm_vcpu_ioctl+0x538/0x620 [kvm] __se_sys_ioctl+0x77/0xc0 __x64_sys_ioctl+0x1d/0x20 do_syscall_64+0x3d/0x80 entry_SYSCALL_64_after_hwframe+0x63/0xcd Fixes: 404d5d7b ("KVM: X86: Introduce more exit_fastpath_completion enum values") Signed-off-by: -
Sean Christopherson authored
Treat any exception during instruction decode for EMULTYPE_SKIP as a "full" emulation failure, i.e. signal failure instead of queuing the exception. When decoding purely to skip an instruction, KVM and/or the CPU has already done some amount of emulation that cannot be unwound, e.g. on an EPT misconfig VM-Exit KVM has already processeed the emulated MMIO. KVM already does this if a #UD is encountered, but not for other exceptions, e.g. if a #PF is encountered during fetch. In SVM's soft-injection use case, queueing the exception is particularly problematic as queueing exceptions while injecting events can put KVM into an infinite loop due to bailing from VM-Enter to service the newly pending exception. E.g. multiple warnings to detect such behavior fire: ------------[ cut here ]------------ WARNING: CPU: 3 PID: 1017 at arch/x86/kvm/x86.c:9873 kvm_arch_vcpu_ioctl_run+0x1de5/0x20a0 [kvm] Modules linked in: kvm_amd ccp kvm irqbypass CPU: 3 PID: 1017 Comm: svm_nested_soft Not tainted 6.0.0-rc1+ #220 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 RIP: 0010:kvm_arch_vcpu_ioctl_run+0x1de5/0x20a0 [kvm] Call Trace: kvm_vcpu_ioctl+0x223/0x6d0 [kvm] __x64_sys_ioctl+0x85/0xc0 do_syscall_64+0x2b/0x50 entry_SYSCALL_64_after_hwframe+0x46/0xb0 ---[ end trace 0000000000000000 ]--- ------------[ cut here ]------------ WARNING: CPU: 3 PID: 1017 at arch/x86/kvm/x86.c:9987 kvm_arch_vcpu_ioctl_run+0x12a3/0x20a0 [kvm] Modules linked in: kvm_amd ccp kvm irqbypass CPU: 3 PID: 1017 Comm: svm_nested_soft Tainted: G W 6.0.0-rc1+ #220 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 RIP: 0010:kvm_arch_vcpu_ioctl_run+0x12a3/0x20a0 [kvm] Call Trace: kvm_vcpu_ioctl+0x223/0x6d0 [kvm] __x64_sys_ioctl+0x85/0xc0 do_syscall_64+0x2b/0x50 entry_SYSCALL_64_after_hwframe+0x46/0xb0 ---[ end trace 0000000000000000 ]--- Fixes: 6ea6e843 ("KVM: x86: inject exceptions produced by x86_decode_insn") Signed-off-by:
-
Peng Hao authored
Acquire SRCU before taking the gpc spinlock in wait_pending_event() so as to be consistent with all other functions that acquire both locks. It's not illegal to acquire SRCU inside a spinlock, nor is there deadlock potential, but in general it's preferable to order locks from least restrictive to most restrictive, e.g. if wait_pending_event() needed to sleep for whatever reason, it could do so while holding SRCU, but would need to drop the spinlock. Signed-off-by:
Peng Hao <flyingpeng@tencent.com> Reviewed-by:
-
- 30 Nov, 2022 6 commits
-
-
Sean Christopherson authored
Resume the guest immediately when injecting a #GP on ECREATE due to an invalid enclave size, i.e. don't attempt ECREATE in the host. The #GP is a terminal fault, e.g. skipping the instruction if ECREATE is successful would result in KVM injecting #GP on the instruction following ECREATE. Fixes: 70210c04 ("KVM: VMX: Add SGX ENCLS[ECREATE] handler to enforce CPUID restrictions") Cc: stable@vger.kernel.org Cc: Kai Huang <kai.huang@intel.com> Signed-off-by:
Kai Huang <kai.huang@intel.com> Link: https://lore.kernel.org/r/20220930233132.1723330-1-seanjc@google.com
-
Paolo Bonzini authored
If a triple fault was fixed by kvm_x86_ops.nested_ops->triple_fault (by turning it into a vmexit), there is no need to leave vcpu_enter_guest(). Any vcpu->requests will be caught later before the actual vmentry, and in fact vcpu_enter_guest() was not initializing the "r" variable. Depending on the compiler's whims, this could cause the x86_64/triple_fault_event_test test to fail. Cc: Maxim Levitsky <mlevitsk@redhat.com> Fixes: 92e7d5c8 ("KVM: x86: allow L1 to not intercept triple fault") Signed-off-by:
-
Michal Luczaj authored
Remove the unused @kvm argument from gpc_unmap_khva(). Signed-off-by:
Michal Luczaj <mhal@rbox.co> Signed-off-by:
David Woodhouse <dwmw@amazon.co.uk> Signed-off-by:
-
Michal Luczaj authored
Formalize "gpc" as the acronym and use it in function names. No functional change intended. Suggested-by:
-
David Woodhouse authored
Torture test the cases where the runstate crosses a page boundary, and and especially the case where it's configured in 32-bit mode and doesn't, but then switching to 64-bit mode makes it go onto the second page. To simplify this, make the KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_ADJUST ioctl also update the guest runstate area. It already did so if the actual runstate changed, as a side-effect of kvm_xen_update_runstate(). So doing it in the plain adjustment case is making it more consistent, as well as giving us a nice way to trigger the update without actually running the vCPU again and changing the values. Signed-off-by:
Paul Durrant <paul@xen.org> Signed-off-by:
-
David Woodhouse authored
Closer inspection of the Xen code shows that we aren't supposed to be using the XEN_RUNSTATE_UPDATE flag unconditionally. It should be explicitly enabled by guests through the HYPERVISOR_vm_assist hypercall. If we randomly set the top bit of ->state_entry_time for a guest that hasn't asked for it and doesn't expect it, that could make the runtimes fail to add up and confuse the guest. Without the flag it's perfectly safe for a vCPU to read its own vcpu_runstate_info; just not for one vCPU to read *another's*. I briefly pondered adding a word for the whole set of VMASST_TYPE_* flags but the only one we care about for HVM guests is this, so it seemed a bit pointless. Signed-off-by:
-
