This check is redundant because the root shadow page will only be a TDP
MMU page if is_tdp_mmu_enabled() returns true, and is_tdp_mmu_enabled()
never changes for the lifetime of a VM.
It's possible that this check was added for performance reasons but it
is unlikely that it is useful in practice since to_shadow_page() is
cheap. That being said, this patch also caches the return value of
is_tdp_mmu_root() in direct_page_fault() since there's no reason to
duplicate the call so many times, so performance is not a concern.
Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: David Matlack <dmatlack@xxxxxxxxxx>
---
arch/x86/kvm/mmu/mmu.c | 11 ++++++-----
arch/x86/kvm/mmu/tdp_mmu.h | 4 +---
2 files changed, 7 insertions(+), 8 deletions(-)
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 0144c40d09c7..1e6bf2e207f6 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3545,7 +3545,7 @@ static bool get_mmio_spte(struct kvm_vcpu *vcpu, u64 addr, u64 *sptep)
return reserved;
}
- if (is_tdp_mmu_root(vcpu->kvm, vcpu->arch.mmu->root_hpa))
+ if (is_tdp_mmu_root(vcpu->arch.mmu->root_hpa))
leaf = kvm_tdp_mmu_get_walk(vcpu, addr, sptes, &root);
else
leaf = get_walk(vcpu, addr, sptes, &root);
@@ -3717,6 +3717,7 @@ static bool try_async_pf(struct kvm_vcpu *vcpu, bool prefault, gfn_t gfn,
static int direct_page_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code,
bool prefault, int max_level, bool is_tdp)
{
+ bool is_tdp_mmu_fault = is_tdp_mmu_root(vcpu->arch.mmu->root_hpa);
bool write = error_code & PFERR_WRITE_MASK;
bool map_writable;
@@ -3729,7 +3730,7 @@ static int direct_page_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code,
if (page_fault_handle_page_track(vcpu, error_code, gfn))
return RET_PF_EMULATE;
- if (!is_tdp_mmu_root(vcpu->kvm, vcpu->arch.mmu->root_hpa)) {
+ if (!is_tdp_mmu_fault) {
r = fast_page_fault(vcpu, gpa, error_code);
if (r != RET_PF_INVALID)
return r;
@@ -3751,7 +3752,7 @@ static int direct_page_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code,
r = RET_PF_RETRY;
- if (is_tdp_mmu_root(vcpu->kvm, vcpu->arch.mmu->root_hpa))
+ if (is_tdp_mmu_fault)
read_lock(&vcpu->kvm->mmu_lock);
else
write_lock(&vcpu->kvm->mmu_lock);
@@ -3762,7 +3763,7 @@ static int direct_page_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code,
if (r)
goto out_unlock;
- if (is_tdp_mmu_root(vcpu->kvm, vcpu->arch.mmu->root_hpa))
+ if (is_tdp_mmu_fault)
r = kvm_tdp_mmu_map(vcpu, gpa, error_code, map_writable, max_level,
pfn, prefault);
else
@@ -3770,7 +3771,7 @@ static int direct_page_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code,
prefault, is_tdp);
out_unlock:
- if (is_tdp_mmu_root(vcpu->kvm, vcpu->arch.mmu->root_hpa))
+ if (is_tdp_mmu_fault)
read_unlock(&vcpu->kvm->mmu_lock);
else
write_unlock(&vcpu->kvm->mmu_lock);
diff --git a/arch/x86/kvm/mmu/tdp_mmu.h b/arch/x86/kvm/mmu/tdp_mmu.h
index 5fdf63090451..843ca2127faf 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.h
+++ b/arch/x86/kvm/mmu/tdp_mmu.h
@@ -91,12 +91,10 @@ static inline bool is_tdp_mmu_enabled(struct kvm *kvm) { return false; }
static inline bool is_tdp_mmu_page(struct kvm_mmu_page *sp) { return false; }
#endif
-static inline bool is_tdp_mmu_root(struct kvm *kvm, hpa_t hpa)
+static inline bool is_tdp_mmu_root(hpa_t hpa)
{
struct kvm_mmu_page *sp;
- if (!is_tdp_mmu_enabled(kvm))
- return false;
if (WARN_ON(!VALID_PAGE(hpa)))
return false;
--
2.32.0.288.g62a8d224e6-goog
