- 24 Oct, 2010 40 commits
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Zachary Amsden authored
Basic informational document about x86 timekeeping and how KVM is affected. Signed-off-by:
Zachary Amsden <zamsden@redhat.com> Signed-off-by:
Marcelo Tosatti <mtosatti@redhat.com>
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Zachary Amsden authored
Kernel time, which advances in discrete steps may progress much slower than TSC. As a result, when kvmclock is adjusted to a new base, the apparent time to the guest, which runs at a much higher, nsec scaled rate based on the current TSC, may have already been observed to have a larger value (kernel_ns + scaled tsc) than the value to which we are setting it (kernel_ns + 0). We must instead compute the clock as potentially observed by the guest for kernel_ns to make sure it does not go backwards. Signed-off-by:
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Zachary Amsden authored
The scale_delta function for shift / multiply with 31-bit precision moves to a common header so it can be used by both kernel and kvm module. Signed-off-by:
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Zachary Amsden authored
If there are active VCPUs which are marked as belonging to a particular hardware CPU, request a clock sync for them when enabling hardware; the TSC could be desynchronized on a newly arriving CPU, and we need to recompute guests system time relative to boot after a suspend event. This covers both cases. Note that it is acceptable to take the spinlock, as either no other tasks will be running and no locks held (BSP after resume), or other tasks will be guaranteed to drop the lock relatively quickly (AP on CPU_STARTING). Noting we now get clock synchronization requests for VCPUs which are starting up (or restarting), it is tempting to attempt to remove the arch/x86/kvm/x86.c CPU hot-notifiers at this time, however it is not correct to do so; they are required for systems with non-constant TSC as the frequency may not be known immediately after the processor has started until the cpufreq driver has had a chance to run and query the chipset. Updated: implement better locking semantics for hardware_enable Removed the hack of dropping and retaking the lock by adding the semantic that we always hold kvm_lock when hardware_enable is called. The one place that doesn't need to worry about it is resume, as resuming a frozen CPU, the spinlock won't be taken. Signed-off-by:
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Zachary Amsden authored
Make the match of TSC find TSC writes that are close to each other instead of perfectly identical; this allows the compensator to also work in migration / suspend scenarios. Signed-off-by:
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Zachary Amsden authored
Add a helper function to compute the kernel time and convert nanoseconds back to CPU specific cycles. Note that these must not be called in preemptible context, as that would mean the kernel could enter software suspend state, which would cause non-atomic operation. Also, convert the KVM_SET_CLOCK / KVM_GET_CLOCK ioctls to use the kernel time helper, these should be bootbased as well. Signed-off-by:
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Zachary Amsden authored
When CPUs with unstable TSCs enter deep C-state, TSC may stop running. This causes us to require resynchronization. Since we can't tell when this may potentially happen, we assume the worst by forcing re-compensation for it at every point the VCPU task is descheduled. Signed-off-by:
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Zachary Amsden authored
Move the TSC control logic from the vendor backends into x86.c by adding adjust_tsc_offset to x86 ops. Now all TSC decisions can be done in one place. Signed-off-by:
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Zachary Amsden authored
If creating an SMP guest with unstable host TSC, issue a warning Signed-off-by:
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Zachary Amsden authored
This simplifies much of the init code; we can now simply always call tsc_khz_changed, optionally passing it a new value, or letting it figure out the existing value (while interrupts are disabled, and thus, by inference from the rule, not raceful against CPU hotplug or frequency updates, which will issue IPIs to the local CPU to perform this very same task). Signed-off-by:
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Zachary Amsden authored
Attempt to synchronize TSCs which are reset to the same value. In the case of a reliable hardware TSC, we can just re-use the same offset, but on non-reliable hardware, we can get closer by adjusting the offset to match the elapsed time. Signed-off-by:
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Zachary Amsden authored
Also, ensure that the storing of the offset and the reading of the TSC are never preempted by taking a spinlock. While the lock is overkill now, it is useful later in this patch series. Signed-off-by:
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Zachary Amsden authored
Change svm / vmx to be the same internally and write TSC offset instead of bare TSC in helper functions. Isolated as a single patch to contain code movement. Signed-off-by:
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Zachary Amsden authored
This is used only by the VMX code, and is not done properly; if the TSC is indeed backwards, it is out of sync, and will need proper handling in the logic at each and every CPU change. For now, drop this test during init as misguided. Signed-off-by:
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Wei Yongjun authored
commit ad05c88266b4cce1c820928ce8a0fb7690912ba1 (KVM: create aggregate kvm_total_used_mmu_pages value) introduce percpu counter kvm_total_used_mmu_pages but never destroy it, this may cause oops when rmmod & modprobe. Signed-off-by:
Wei Yongjun <yjwei@cn.fujitsu.com> Acked-by:
Tim Pepper <lnxninja@linux.vnet.ibm.com> Signed-off-by:
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Xiaotian Feng authored
Latest kvm mmu_shrink code rework makes kernel changes kvm->arch.n_used_mmu_pages/ kvm->arch.n_max_mmu_pages at kvm_mmu_free_page/kvm_mmu_alloc_page, which is called by kvm_mmu_commit_zap_page. So the kvm->arch.n_used_mmu_pages or kvm_mmu_available_pages(vcpu->kvm) is unchanged after kvm_mmu_prepare_zap_page(), This caused kvm_mmu_change_mmu_pages/__kvm_mmu_free_some_pages loops forever. Moving kvm_mmu_commit_zap_page would make the while loop performs as normal. Reported-by:
Avi Kivity <avi@redhat.com> Signed-off-by:
Xiaotian Feng <dfeng@redhat.com> Tested-by:
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Wei Yongjun authored
Add JrCXZ instruction emulation (opcode 0xe3) Used by FreeBSD boot loader. Signed-off-by:
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Wei Yongjun authored
Add LDS/LES/LFS/LGS/LSS instruction emulation. (opcode 0xc4, 0xc5, 0x0f 0xb2, 0x0f 0xb4~0xb5) Signed-off-by:
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Dave Hansen authored
Of slab shrinkers, the VM code says: * Note that 'shrink' will be passed nr_to_scan == 0 when the VM is * querying the cache size, so a fastpath for that case is appropriate. and it *means* it. Look at how it calls the shrinkers: nr_before = (*shrinker->shrink)(0, gfp_mask); shrink_ret = (*shrinker->shrink)(this_scan, gfp_mask); So, if you do anything stupid in your shrinker, the VM will doubly punish you. The mmu_shrink() function takes the global kvm_lock, then acquires every VM's kvm->mmu_lock in sequence. If we have 100 VMs, then we're going to take 101 locks. We do it twice, so each call takes 202 locks. If we're under memory pressure, we can have each cpu trying to do this. It can get really hairy, and we've seen lock spinning in mmu_shrink() be the dominant entry in profiles. This is guaranteed to optimize at least half of those lock aquisitions away. It removes the need to take any of the locks when simply trying to count objects. A 'percpu_counter' can be a large object, but we only have one of these for the entire system. There are not any better alternatives at the moment, especially ones that handle CPU hotplug. Signed-off-by:Dave Hansen <dave@linux.vnet.ibm.com> Signed-off-by:
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Dave Hansen authored
Doing this makes the code much more readable. That's borne out by the fact that this patch removes code. "used" also happens to be the number that we need to return back to the slab code when our shrinker gets called. Keeping this value as opposed to free makes the next patch simpler. So, 'struct kvm' is kzalloc()'d. 'struct kvm_arch' is a structure member (and not a pointer) of 'struct kvm'. That means they start out zeroed. I _think_ they get initialized properly by kvm_mmu_change_mmu_pages(). But, that only happens via kvm ioctls. Another benefit of storing 'used' intead of 'free' is that the values are consistent from the moment the structure is allocated: no negative "used" value. Signed-off-by:
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Dave Hansen authored
arch.n_alloc_mmu_pages is a poor choice of name. This value truly means, "the number of pages which _may_ be allocated". But, reading the name, "n_alloc_mmu_pages" implies "the number of allocated mmu pages", which is dead wrong. It's really the high watermark, so let's give it a name to match: nr_max_mmu_pages. This change will make the next few patches much more obvious and easy to read. Signed-off-by:
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Dave Hansen authored
"free" is a poor name for this value. In this context, it means, "the number of mmu pages which this kvm instance should be able to allocate." But "free" implies much more that the objects are there and ready for use. "available" is a much better description, especially when you see how it is calculated. In this patch, we abstract its use into a function. We'll soon replace the function's contents by calculating the value in a different way. All of the reads of n_free_mmu_pages are taken care of in this patch. The modification sites will be handled in a patch later in the series. Signed-off-by:
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Avi Kivity authored
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Avi Kivity authored
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Avi Kivity authored
Needed for 3-operand IMUL. Signed-off-by: -
Avi Kivity authored
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Avi Kivity authored
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Avi Kivity authored
Useless. Signed-off-by: -
Avi Kivity authored
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Avi Kivity authored
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Avi Kivity authored
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Avi Kivity authored
Used for RET NEAR instructions. Signed-off-by: -
Avi Kivity authored
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Avi Kivity authored
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Avi Kivity authored
Most x86 two operand instructions allow the destination to be a memory operand, but IMUL (for example) requires that the destination be a register. Change ____emulate_2op() to take a register for both source and destination so we can invoke IMUL. Signed-off-by: -
Avi Kivity authored
We'll need it later so we can use a register for the destination. Signed-off-by: -
Wei Yongjun authored
Add LOOP/LOOPcc instruction emulation (opcode 0xe0~0xe2). Signed-off-by:
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Wei Yongjun authored
Add CBW/CWDE/CDQE instruction emulation.(opcode 0x98) Used by FreeBSD's boot loader. Signed-off-by:
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Avi Kivity authored
EFLAGS.ZF needs to be checked after each iteration, not before. Signed-off-by: -
Avi Kivity authored
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