| Message ID | 20220203010051.2813563-16-dmatlack@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Extend Eager Page Splitting to the shadow MMU | expand |
On Wed, Feb 2, 2022 at 5:02 PM David Matlack <dmatlack@google.com> wrote: > > Currently make_huge_page_split_spte() assumes execute permissions can be > granted to any 4K SPTE when splitting huge pages. This is true for the > TDP MMU but is not necessarily true for the shadow MMU. Huge pages > mapped by the shadow MMU may be shadowing huge pages that the guest has > disallowed execute permissions. > > No functional change intended. > Reviewed-by: Ben Gardon <bgardon@google.com> > Signed-off-by: David Matlack <dmatlack@google.com> > --- > arch/x86/kvm/mmu/spte.c | 5 +++-- > arch/x86/kvm/mmu/spte.h | 3 ++- > arch/x86/kvm/mmu/tdp_mmu.c | 2 +- > 3 files changed, 6 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/kvm/mmu/spte.c b/arch/x86/kvm/mmu/spte.c > index 20cf9e0d45dd..7cba5cffc240 100644 > --- a/arch/x86/kvm/mmu/spte.c > +++ b/arch/x86/kvm/mmu/spte.c > @@ -215,7 +215,8 @@ static u64 make_spte_executable(u64 spte) > * This is used during huge page splitting to build the SPTEs that make up the > * new page table. > */ > -u64 make_huge_page_split_spte(u64 huge_spte, int huge_level, int index) > +u64 make_huge_page_split_spte(u64 huge_spte, int huge_level, int index, > + unsigned int access) > { > u64 child_spte; > int child_level; > @@ -243,7 +244,7 @@ u64 make_huge_page_split_spte(u64 huge_spte, int huge_level, int index) > * When splitting to a 4K page, mark the page executable as the > * NX hugepage mitigation no longer applies. > */ > - if (is_nx_huge_page_enabled()) > + if (is_nx_huge_page_enabled() && (access & ACC_EXEC_MASK)) > child_spte = make_spte_executable(child_spte); > } > > diff --git a/arch/x86/kvm/mmu/spte.h b/arch/x86/kvm/mmu/spte.h > index 73f12615416f..c7ccdd5c440d 100644 > --- a/arch/x86/kvm/mmu/spte.h > +++ b/arch/x86/kvm/mmu/spte.h > @@ -415,7 +415,8 @@ bool make_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, > unsigned int pte_access, gfn_t gfn, kvm_pfn_t pfn, > u64 old_spte, bool prefetch, bool can_unsync, > bool host_writable, u64 *new_spte); > -u64 make_huge_page_split_spte(u64 huge_spte, int huge_level, int index); > +u64 make_huge_page_split_spte(u64 huge_spte, int huge_level, int index, > + unsigned int access); > u64 make_nonleaf_spte(u64 *child_pt, bool ad_disabled); > u64 make_mmio_spte(struct kvm_vcpu *vcpu, u64 gfn, unsigned int access); > u64 mark_spte_for_access_track(u64 spte); > diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c > index 34c451f1eac9..02bfbc1bebbe 100644 > --- a/arch/x86/kvm/mmu/tdp_mmu.c > +++ b/arch/x86/kvm/mmu/tdp_mmu.c > @@ -1310,7 +1310,7 @@ static int tdp_mmu_split_huge_page(struct kvm *kvm, struct tdp_iter *iter, > * not been linked in yet and thus is not reachable from any other CPU. > */ > for (i = 0; i < PT64_ENT_PER_PAGE; i++) > - sp->spt[i] = make_huge_page_split_spte(huge_spte, level, i); > + sp->spt[i] = make_huge_page_split_spte(huge_spte, level, i, ACC_ALL); > > /* > * Replace the huge spte with a pointer to the populated lower level > -- > 2.35.0.rc2.247.g8bbb082509-goog >
diff --git a/arch/x86/kvm/mmu/spte.c b/arch/x86/kvm/mmu/spte.c index 20cf9e0d45dd..7cba5cffc240 100644 --- a/arch/x86/kvm/mmu/spte.c +++ b/arch/x86/kvm/mmu/spte.c @@ -215,7 +215,8 @@ static u64 make_spte_executable(u64 spte) * This is used during huge page splitting to build the SPTEs that make up the * new page table. */ -u64 make_huge_page_split_spte(u64 huge_spte, int huge_level, int index) +u64 make_huge_page_split_spte(u64 huge_spte, int huge_level, int index, + unsigned int access) { u64 child_spte; int child_level; @@ -243,7 +244,7 @@ u64 make_huge_page_split_spte(u64 huge_spte, int huge_level, int index) * When splitting to a 4K page, mark the page executable as the * NX hugepage mitigation no longer applies. */ - if (is_nx_huge_page_enabled()) + if (is_nx_huge_page_enabled() && (access & ACC_EXEC_MASK)) child_spte = make_spte_executable(child_spte); } diff --git a/arch/x86/kvm/mmu/spte.h b/arch/x86/kvm/mmu/spte.h index 73f12615416f..c7ccdd5c440d 100644 --- a/arch/x86/kvm/mmu/spte.h +++ b/arch/x86/kvm/mmu/spte.h @@ -415,7 +415,8 @@ bool make_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, unsigned int pte_access, gfn_t gfn, kvm_pfn_t pfn, u64 old_spte, bool prefetch, bool can_unsync, bool host_writable, u64 *new_spte); -u64 make_huge_page_split_spte(u64 huge_spte, int huge_level, int index); +u64 make_huge_page_split_spte(u64 huge_spte, int huge_level, int index, + unsigned int access); u64 make_nonleaf_spte(u64 *child_pt, bool ad_disabled); u64 make_mmio_spte(struct kvm_vcpu *vcpu, u64 gfn, unsigned int access); u64 mark_spte_for_access_track(u64 spte); diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index 34c451f1eac9..02bfbc1bebbe 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -1310,7 +1310,7 @@ static int tdp_mmu_split_huge_page(struct kvm *kvm, struct tdp_iter *iter, * not been linked in yet and thus is not reachable from any other CPU. */ for (i = 0; i < PT64_ENT_PER_PAGE; i++) - sp->spt[i] = make_huge_page_split_spte(huge_spte, level, i); + sp->spt[i] = make_huge_page_split_spte(huge_spte, level, i, ACC_ALL); /* * Replace the huge spte with a pointer to the populated lower level
Currently make_huge_page_split_spte() assumes execute permissions can be granted to any 4K SPTE when splitting huge pages. This is true for the TDP MMU but is not necessarily true for the shadow MMU. Huge pages mapped by the shadow MMU may be shadowing huge pages that the guest has disallowed execute permissions. No functional change intended. Signed-off-by: David Matlack <dmatlack@google.com> --- arch/x86/kvm/mmu/spte.c | 5 +++-- arch/x86/kvm/mmu/spte.h | 3 ++- arch/x86/kvm/mmu/tdp_mmu.c | 2 +- 3 files changed, 6 insertions(+), 4 deletions(-)