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-rw-r--r--arch/x86/include/asm/kvm_host.h7
-rw-r--r--arch/x86/kvm/mmu.c38
-rw-r--r--arch/x86/kvm/mmu.h19
-rw-r--r--arch/x86/kvm/paging_tmpl.h22
-rw-r--r--arch/x86/kvm/x86.c11
5 files changed, 61 insertions, 36 deletions
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 64adb61..3318bde 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -287,6 +287,13 @@ struct kvm_mmu {
union kvm_mmu_page_role base_role;
bool direct_map;
+ /*
+ * Bitmap; bit set = permission fault
+ * Byte index: page fault error code [4:1]
+ * Bit index: pte permissions in ACC_* format
+ */
+ u8 permissions[16];
+
u64 *pae_root;
u64 *lm_root;
u64 rsvd_bits_mask[2][4];
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index f297a2c..9c61889 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -3516,6 +3516,38 @@ static void reset_rsvds_bits_mask(struct kvm_vcpu *vcpu,
}
}
+static void update_permission_bitmask(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu)
+{
+ unsigned bit, byte, pfec;
+ u8 map;
+ bool fault, x, w, u, wf, uf, ff, smep;
+
+ smep = kvm_read_cr4_bits(vcpu, X86_CR4_SMEP);
+ for (byte = 0; byte < ARRAY_SIZE(mmu->permissions); ++byte) {
+ pfec = byte << 1;
+ map = 0;
+ wf = pfec & PFERR_WRITE_MASK;
+ uf = pfec & PFERR_USER_MASK;
+ ff = pfec & PFERR_FETCH_MASK;
+ for (bit = 0; bit < 8; ++bit) {
+ x = bit & ACC_EXEC_MASK;
+ w = bit & ACC_WRITE_MASK;
+ u = bit & ACC_USER_MASK;
+
+ /* Not really needed: !nx will cause pte.nx to fault */
+ x |= !mmu->nx;
+ /* Allow supervisor writes if !cr0.wp */
+ w |= !is_write_protection(vcpu) && !uf;
+ /* Disallow supervisor fetches of user code if cr4.smep */
+ x &= !(smep && u && !uf);
+
+ fault = (ff && !x) || (uf && !u) || (wf && !w);
+ map |= fault << bit;
+ }
+ mmu->permissions[byte] = map;
+ }
+}
+
static int paging64_init_context_common(struct kvm_vcpu *vcpu,
struct kvm_mmu *context,
int level)
@@ -3524,6 +3556,7 @@ static int paging64_init_context_common(struct kvm_vcpu *vcpu,
context->root_level = level;
reset_rsvds_bits_mask(vcpu, context);
+ update_permission_bitmask(vcpu, context);
ASSERT(is_pae(vcpu));
context->new_cr3 = paging_new_cr3;
@@ -3552,6 +3585,7 @@ static int paging32_init_context(struct kvm_vcpu *vcpu,
context->root_level = PT32_ROOT_LEVEL;
reset_rsvds_bits_mask(vcpu, context);
+ update_permission_bitmask(vcpu, context);
context->new_cr3 = paging_new_cr3;
context->page_fault = paging32_page_fault;
@@ -3612,6 +3646,8 @@ static int init_kvm_tdp_mmu(struct kvm_vcpu *vcpu)
context->gva_to_gpa = paging32_gva_to_gpa;
}
+ update_permission_bitmask(vcpu, context);
+
return 0;
}
@@ -3687,6 +3723,8 @@ static int init_kvm_nested_mmu(struct kvm_vcpu *vcpu)
g_context->gva_to_gpa = paging32_gva_to_gpa_nested;
}
+ update_permission_bitmask(vcpu, g_context);
+
return 0;
}
diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index 2832081..5846607 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -89,17 +89,14 @@ static inline bool is_write_protection(struct kvm_vcpu *vcpu)
return kvm_read_cr0_bits(vcpu, X86_CR0_WP);
}
-static inline bool check_write_user_access(struct kvm_vcpu *vcpu,
- bool write_fault, bool user_fault,
- unsigned long pte)
+/*
+ * Will a fault with a given page-fault error code (pfec) cause a permission
+ * fault with the given access (in ACC_* format)?
+ */
+static inline bool permission_fault(struct kvm_mmu *mmu, unsigned pte_access,
+ unsigned pfec)
{
- if (unlikely(write_fault && !is_writable_pte(pte)
- && (user_fault || is_write_protection(vcpu))))
- return false;
-
- if (unlikely(user_fault && !(pte & PT_USER_MASK)))
- return false;
-
- return true;
+ return (mmu->permissions[pfec >> 1] >> pte_access) & 1;
}
+
#endif
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 35a05dd..8f6c59f 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -169,7 +169,7 @@ 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, uninitialized_var(pte_access);
+ unsigned index, pt_access, pte_access;
gpa_t pte_gpa;
bool eperm, last_gpte;
int offset;
@@ -237,24 +237,9 @@ retry_walk:
goto error;
}
- if (!check_write_user_access(vcpu, write_fault, user_fault,
- pte))
- eperm = true;
-
-#if PTTYPE == 64
- if (unlikely(fetch_fault && (pte & PT64_NX_MASK)))
- eperm = true;
-#endif
+ pte_access = pt_access & gpte_access(vcpu, pte);
last_gpte = FNAME(is_last_gpte)(walker, vcpu, mmu, pte);
- if (last_gpte) {
- pte_access = pt_access & gpte_access(vcpu, pte);
- /* check if the kernel is fetching from user page */
- if (unlikely(pte_access & PT_USER_MASK) &&
- kvm_read_cr4_bits(vcpu, X86_CR4_SMEP))
- if (fetch_fault && !user_fault)
- eperm = true;
- }
walker->ptes[walker->level - 1] = pte;
@@ -284,10 +269,11 @@ retry_walk:
break;
}
- pt_access &= gpte_access(vcpu, pte);
+ pt_access &= pte_access;
--walker->level;
}
+ eperm |= permission_fault(mmu, pte_access, access);
if (unlikely(eperm)) {
errcode |= PFERR_PRESENT_MASK;
goto error;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 19047ea..497226e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3672,20 +3672,17 @@ static int vcpu_mmio_gva_to_gpa(struct kvm_vcpu *vcpu, unsigned long gva,
gpa_t *gpa, struct x86_exception *exception,
bool write)
{
- u32 access = (kvm_x86_ops->get_cpl(vcpu) == 3) ? PFERR_USER_MASK : 0;
+ u32 access = ((kvm_x86_ops->get_cpl(vcpu) == 3) ? PFERR_USER_MASK : 0)
+ | (write ? PFERR_WRITE_MASK : 0);
- if (vcpu_match_mmio_gva(vcpu, gva) &&
- check_write_user_access(vcpu, write, access,
- vcpu->arch.access)) {
+ if (vcpu_match_mmio_gva(vcpu, gva)
+ && !permission_fault(vcpu->arch.walk_mmu, vcpu->arch.access, access)) {
*gpa = vcpu->arch.mmio_gfn << PAGE_SHIFT |
(gva & (PAGE_SIZE - 1));
trace_vcpu_match_mmio(gva, *gpa, write, false);
return 1;
}
- if (write)
- access |= PFERR_WRITE_MASK;
-
*gpa = vcpu->arch.walk_mmu->gva_to_gpa(vcpu, gva, access, exception);
if (*gpa == UNMAPPED_GVA)
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