[PATCH 52/54] KVM: x86/mmu: Get CR0.WP from MMU, not vCPU, in shadow page fault

From: Sean Christopherson
Date: Tue Jun 22 2021 - 14:05:32 EST


Use the current MMU instead of vCPU state to query CR0.WP when handling
a page fault. In the nested NPT case, the current CR0.WP reflects L2,
whereas the page fault is shadowing L1's NPT. Practically speaking, this
is a nop a NPT walks are always user faults, but fix it up for
consistency.

Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
arch/x86/kvm/mmu.h | 5 -----
arch/x86/kvm/mmu/paging_tmpl.h | 5 ++---
2 files changed, 2 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index 62844bacd13f..83e6c6965f1e 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -165,11 +165,6 @@ static inline bool is_writable_pte(unsigned long pte)
return pte & PT_WRITABLE_MASK;
}

-static inline bool is_write_protection(struct kvm_vcpu *vcpu)
-{
- return kvm_read_cr0_bits(vcpu, X86_CR0_WP);
-}
-
/*
* Check if a given access (described through the I/D, W/R and U/S bits of a
* page fault error code pfec) causes a permission fault with the given PTE
diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
index ec1de57f3572..260a9c06d764 100644
--- a/arch/x86/kvm/mmu/paging_tmpl.h
+++ b/arch/x86/kvm/mmu/paging_tmpl.h
@@ -795,7 +795,7 @@ FNAME(is_self_change_mapping)(struct kvm_vcpu *vcpu,
bool self_changed = false;

if (!(walker->pte_access & ACC_WRITE_MASK ||
- (!is_write_protection(vcpu) && !user_fault)))
+ (!is_cr0_wp(vcpu->arch.mmu) && !user_fault)))
return false;

for (level = walker->level; level <= walker->max_level; level++) {
@@ -893,8 +893,7 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gpa_t addr, u32 error_code,
* we will cache the incorrect access into mmio spte.
*/
if (write_fault && !(walker.pte_access & ACC_WRITE_MASK) &&
- !is_write_protection(vcpu) && !user_fault &&
- !is_noslot_pfn(pfn)) {
+ !is_cr0_wp(vcpu->arch.mmu) && !user_fault && !is_noslot_pfn(pfn)) {
walker.pte_access |= ACC_WRITE_MASK;
walker.pte_access &= ~ACC_USER_MASK;

--
2.32.0.288.g62a8d224e6-goog