KVM: MMU: Fix regression with ept memory types merged into non-ept page tables
PATCH 1/1 KVM: MMU: Fix regression with ept memory types merged into non-ept page tables
Commit "KVM: MMU: Make tdp_enabled a mmu-context parameter" made real-mode set ->direct_map, and changed the code that merges in the memory type depend on direct_map instead of tdp_enabled. However, in this case what really matters is tdp, not direct_map, since tdp changes the pte format regardless of whether the mapping is direct or not.
As a result, real-mode shadow mappings got corrupted with ept memory types. The result was a huge slowdown, likely due to the cache being disabled.
Change it back as the simplest fix for the regression (real fix is to move all that to vmx code, and not use tdp_enabled as a synonym for ept).
--- arch/x86/kvm/mmu.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-)
arch/x86/kvm/mmu.c +1 -1
@@ -1980,7 +1980,7 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep, spte |= shadow_user_mask;if (level >PT_PAGE_TABLE_LEVEL ) spte |=PT_PAGE_SIZE_MASK ; -if (vcpu->arch.mmu.direct_map) +if (tdp_enabled) spte |= kvm_x86_ops->get_mt_mask (vcpu, gfn,kvm_is_mmio_pfn (pfn));
Signature · 1 line
1.7.1
Quoted 22 lines · Avi Kivity
Commit "KVM: MMU: Make
tdp_enableda mmu-context parameter" made real-mode set ->direct_map, and changed the code that merges in the memory type depend ondirect_mapinstead oftdp_enabled. However, in this case what really matters is tdp, notdirect_map, since tdp changes the pte format regardless of whether the mapping is direct or not.As a result, real-mode shadow mappings got corrupted with ept memory types. The result was a huge slowdown, likely due to the cache being disabled.
Change it back as the simplest fix for the regression (real fix is to move all that to vmx code, and not use
tdp_enabledas a synonym for ept).Signed-off-by Avi Kivity <[email protected]>--- arch/x86/kvm/mmu.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-)arch/x86/kvm/mmu.c +0
-0
arch/x86/kvm/mmu.c static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep, · line 1985
Quoted 7 lines
arch/x86/kvm/mmu.c +1
-1@@ -1980,7 +1980,7 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep, spte |= shadow_user_mask;if (level >PT_PAGE_TABLE_LEVEL ) spte |=PT_PAGE_SIZE_MASK ; -if (vcpu->arch.mmu.direct_map) +if (tdp_enabled) spte |= kvm_x86_ops->get_mt_mask (vcpu, gfn,kvm_is_mmio_pfn (pfn));
Oh, indeed. Thanks for fixing this.