[PATCH v2 17/26] KVM: x86/mmu: Pass access information to make_huge_page_split_spte()

David Matlack
2022-03-11T00:26:05Z

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 d10189d9c877..7294f95464a7 100644
--- a/arch/x86/kvm/mmu/spte.c
+++ b/arch/x86/kvm/mmu/spte.c
@@ -216,7 +216,8 @@ 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;
@@ -244,7 +245,7 @@ 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 85b7bc333302..541b145b2df2 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -1430,7 +1430,7 @@ 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
--
2.35.1.723.g4982287a31-goog