KVM, pkeys: add pkeys support for permission_fault

Protection keys define a new 4-bit protection key field (PKEY) in bits
62:59 of leaf entries of the page tables, the PKEY is an index to PKRU
register(16 domains), every domain has 2 bits(write disable bit, access
disable bit).

Static logic has been produced in update_pkru_bitmask, dynamic logic need
read pkey from page table entries, get pkru value, and deduce the correct
result.

[ Huaitong: Xiao helps to modify many sections. ]
Signed-off-by: Huaitong Han <huaitong.han@intel.com>
Signed-off-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -187,12 +187,14 @@ enum {
 #define PFERR_USER_BIT 2
 #define PFERR_RSVD_BIT 3
 #define PFERR_FETCH_BIT 4
+#define PFERR_PK_BIT 5
 
 #define PFERR_PRESENT_MASK (1U << PFERR_PRESENT_BIT)
 #define PFERR_WRITE_MASK (1U << PFERR_WRITE_BIT)
 #define PFERR_USER_MASK (1U << PFERR_USER_BIT)
 #define PFERR_RSVD_MASK (1U << PFERR_RSVD_BIT)
 #define PFERR_FETCH_MASK (1U << PFERR_FETCH_BIT)
+#define PFERR_PK_MASK (1U << PFERR_PK_BIT)
 
 /* apic attention bits */
 #define KVM_APIC_CHECK_VAPIC	0
@@ -882,6 +884,7 @@ struct kvm_x86_ops {
 	void (*cache_reg)(struct kvm_vcpu *vcpu, enum kvm_reg reg);
 	unsigned long (*get_rflags)(struct kvm_vcpu *vcpu);
 	void (*set_rflags)(struct kvm_vcpu *vcpu, unsigned long rflags);
+	u32 (*get_pkru)(struct kvm_vcpu *vcpu);
 	void (*fpu_activate)(struct kvm_vcpu *vcpu);
 	void (*fpu_deactivate)(struct kvm_vcpu *vcpu);
 

arch/x86/kvm/kvm_cache_regs.h

@@ -84,6 +84,11 @@ static inline u64 kvm_read_edx_eax(struct kvm_vcpu *vcpu)
 		| ((u64)(kvm_register_read(vcpu, VCPU_REGS_RDX) & -1u) << 32);
 }
 
+static inline u32 kvm_read_pkru(struct kvm_vcpu *vcpu)
+{
+	return kvm_x86_ops->get_pkru(vcpu);
+}
+
 static inline void enter_guest_mode(struct kvm_vcpu *vcpu)
 {
 	vcpu->arch.hflags |= HF_GUEST_MASK;

arch/x86/kvm/mmu.h

@@ -10,10 +10,11 @@
 #define PT32_ENT_PER_PAGE (1 << PT32_PT_BITS)
 
 #define PT_WRITABLE_SHIFT 1
+#define PT_USER_SHIFT 2
 
 #define PT_PRESENT_MASK (1ULL << 0)
 #define PT_WRITABLE_MASK (1ULL << PT_WRITABLE_SHIFT)
-#define PT_USER_MASK (1ULL << 2)
+#define PT_USER_MASK (1ULL << PT_USER_SHIFT)
 #define PT_PWT_MASK (1ULL << 3)
 #define PT_PCD_MASK (1ULL << 4)
 #define PT_ACCESSED_SHIFT 5
@@ -149,7 +150,8 @@ static inline bool is_write_protection(struct kvm_vcpu *vcpu)
  * if the access faults.
  */
 static inline u8 permission_fault(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
-				  unsigned pte_access, unsigned pfec)
+				  unsigned pte_access, unsigned pte_pkey,
+				  unsigned pfec)
 {
 	int cpl = kvm_x86_ops->get_cpl(vcpu);
 	unsigned long rflags = kvm_x86_ops->get_rflags(vcpu);
@@ -170,11 +172,32 @@ static inline u8 permission_fault(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
 	unsigned long smap = (cpl - 3) & (rflags & X86_EFLAGS_AC);
 	int index = (pfec >> 1) +
 		    (smap >> (X86_EFLAGS_AC_BIT - PFERR_RSVD_BIT + 1));
+	bool fault = (mmu->permissions[index] >> pte_access) & 1;
 
-	WARN_ON(pfec & PFERR_RSVD_MASK);
-
+	WARN_ON(pfec & (PFERR_PK_MASK | PFERR_RSVD_MASK));
 	pfec |= PFERR_PRESENT_MASK;
-	return -((mmu->permissions[index] >> pte_access) & 1) & pfec;
+
+	if (unlikely(mmu->pkru_mask)) {
+		u32 pkru_bits, offset;
+
+		/*
+		* PKRU defines 32 bits, there are 16 domains and 2
+		* attribute bits per domain in pkru.  pte_pkey is the
+		* index of the protection domain, so pte_pkey * 2 is
+		* is the index of the first bit for the domain.
+		*/
+		pkru_bits = (kvm_read_pkru(vcpu) >> (pte_pkey * 2)) & 3;
+
+		/* clear present bit, replace PFEC.RSVD with ACC_USER_MASK. */
+		offset = pfec - 1 +
+			((pte_access & PT_USER_MASK) << (PFERR_RSVD_BIT - PT_USER_SHIFT));
+
+		pkru_bits &= mmu->pkru_mask >> offset;
+		pfec |= -pkru_bits & PFERR_PK_MASK;
+		fault |= (pkru_bits != 0);
+	}
+
+	return -(uint32_t)fault & pfec;
 }
 
 void kvm_mmu_invalidate_zap_all_pages(struct kvm *kvm);

arch/x86/kvm/paging_tmpl.h

@@ -257,6 +257,17 @@ static int FNAME(update_accessed_dirty_bits)(struct kvm_vcpu *vcpu,
 	return 0;
 }
 
+static inline unsigned FNAME(gpte_pkeys)(struct kvm_vcpu *vcpu, u64 gpte)
+{
+	unsigned pkeys = 0;
+#if PTTYPE == 64
+	pte_t pte = {.pte = gpte};
+
+	pkeys = pte_flags_pkey(pte_flags(pte));
+#endif
+	return pkeys;
+}
+
 /*
  * Fetch a guest pte for a guest virtual address
  */
@@ -268,7 +279,7 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker,
 	pt_element_t pte;
 	pt_element_t __user *uninitialized_var(ptep_user);
 	gfn_t table_gfn;
-	unsigned index, pt_access, pte_access, accessed_dirty;
+	unsigned index, pt_access, pte_access, accessed_dirty, pte_pkey;
 	gpa_t pte_gpa;
 	int offset;
 	const int write_fault = access & PFERR_WRITE_MASK;
@@ -359,7 +370,8 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker,
 		walker->ptes[walker->level - 1] = pte;
 	} while (!is_last_gpte(mmu, walker->level, pte));
 
-	errcode = permission_fault(vcpu, mmu, pte_access, access);
+	pte_pkey = FNAME(gpte_pkeys)(vcpu, pte);
+	errcode = permission_fault(vcpu, mmu, pte_access, pte_pkey, access);
 	if (unlikely(errcode))
 		goto error;
 

arch/x86/kvm/svm.c

@@ -1280,6 +1280,11 @@ static void svm_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags)
 	to_svm(vcpu)->vmcb->save.rflags = rflags;
 }
 
+static u32 svm_get_pkru(struct kvm_vcpu *vcpu)
+{
+	return 0;
+}
+
 static void svm_cache_reg(struct kvm_vcpu *vcpu, enum kvm_reg reg)
 {
 	switch (reg) {
@@ -4347,6 +4352,9 @@ static struct kvm_x86_ops svm_x86_ops = {
 	.cache_reg = svm_cache_reg,
 	.get_rflags = svm_get_rflags,
 	.set_rflags = svm_set_rflags,
+
+	.get_pkru = svm_get_pkru,
+
 	.fpu_activate = svm_fpu_activate,
 	.fpu_deactivate = svm_fpu_deactivate,
 

arch/x86/kvm/vmx.c

@@ -2292,6 +2292,11 @@ static void vmx_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags)
 	vmcs_writel(GUEST_RFLAGS, rflags);
 }
 
+static u32 vmx_get_pkru(struct kvm_vcpu *vcpu)
+{
+	return to_vmx(vcpu)->guest_pkru;
+}
+
 static u32 vmx_get_interrupt_shadow(struct kvm_vcpu *vcpu)
 {
 	u32 interruptibility = vmcs_read32(GUEST_INTERRUPTIBILITY_INFO);
@@ -10925,6 +10930,9 @@ static struct kvm_x86_ops vmx_x86_ops = {
 	.cache_reg = vmx_cache_reg,
 	.get_rflags = vmx_get_rflags,
 	.set_rflags = vmx_set_rflags,
+
+	.get_pkru = vmx_get_pkru,
+
 	.fpu_activate = vmx_fpu_activate,
 	.fpu_deactivate = vmx_fpu_deactivate,
 

arch/x86/kvm/x86.c

@@ -4326,9 +4326,14 @@ static int vcpu_mmio_gva_to_gpa(struct kvm_vcpu *vcpu, unsigned long gva,
 	u32 access = ((kvm_x86_ops->get_cpl(vcpu) == 3) ? PFERR_USER_MASK : 0)
 		| (write ? PFERR_WRITE_MASK : 0);
 
+	/*
+	 * currently PKRU is only applied to ept enabled guest so
+	 * there is no pkey in EPT page table for L1 guest or EPT
+	 * shadow page table for L2 guest.
+	 */
 	if (vcpu_match_mmio_gva(vcpu, gva)
 	    && !permission_fault(vcpu, vcpu->arch.walk_mmu,
-				 vcpu->arch.access, access)) {
+				 vcpu->arch.access, 0, access)) {
 		*gpa = vcpu->arch.mmio_gfn << PAGE_SHIFT |
 					(gva & (PAGE_SIZE - 1));
 		trace_vcpu_match_mmio(gva, *gpa, write, false);