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KVM: selftests: Set the user bit on nested NPT PTEs

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According to the APM, NPT walks are treated as user accesses. In
preparation for supporting NPT mappings, set the 'user' bit on NPTs by
adding a mask of bits to always be set on PTEs in kvm_mmu.

Signed-off-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Link: https://patch.msgid.link/20251230230150.4150236-18-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Yosry Ahmed 2025-12-30 15:01:46 -08:00 committed by Sean Christopherson
parent 753c0d5a50
commit 251e4849a7
4 changed files with 9 additions and 2 deletions
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2
tools/testing/selftests/kvm/include/x86/kvm_util_arch.h
View File

@ -22,6 +22,8 @@ struct pte_masks {
uint64_t nx;
uint64_t c;
uint64_t s;
uint64_t always_set;
};
struct kvm_mmu_arch {

1
tools/testing/selftests/kvm/include/x86/processor.h
View File

@ -1452,6 +1452,7 @@ enum pg_level {
#define PTE_NX_MASK(mmu) ((mmu)->arch.pte_masks.nx)
#define PTE_C_BIT_MASK(mmu) ((mmu)->arch.pte_masks.c)
#define PTE_S_BIT_MASK(mmu) ((mmu)->arch.pte_masks.s)
#define PTE_ALWAYS_SET_MASK(mmu) ((mmu)->arch.pte_masks.always_set)
/*
* For PTEs without a PRESENT bit (i.e. EPT entries), treat the PTE as present

5
tools/testing/selftests/kvm/lib/x86/processor.c
View File

@ -231,7 +231,8 @@ static uint64_t *virt_create_upper_pte(struct kvm_vm *vm,
if (!is_present_pte(mmu, pte)) {
*pte = PTE_PRESENT_MASK(mmu) | PTE_READABLE_MASK(mmu) |
PTE_WRITABLE_MASK(mmu) | PTE_EXECUTABLE_MASK(mmu);
PTE_WRITABLE_MASK(mmu) | PTE_EXECUTABLE_MASK(mmu) |
PTE_ALWAYS_SET_MASK(mmu);
if (current_level == target_level)
*pte |= PTE_HUGE_MASK(mmu) | (paddr & PHYSICAL_PAGE_MASK);
else
@ -299,7 +300,7 @@ void __virt_pg_map(struct kvm_vm *vm, struct kvm_mmu *mmu, uint64_t vaddr,
"PTE already present for 4k page at vaddr: 0x%lx", vaddr);
*pte = PTE_PRESENT_MASK(mmu) | PTE_READABLE_MASK(mmu) |
PTE_WRITABLE_MASK(mmu) | PTE_EXECUTABLE_MASK(mmu) |
(paddr & PHYSICAL_PAGE_MASK);
PTE_ALWAYS_SET_MASK(mmu) | (paddr & PHYSICAL_PAGE_MASK);
/*
* Neither SEV nor TDX supports shared page tables, so only the final

3
tools/testing/selftests/kvm/lib/x86/svm.c
View File

@ -75,6 +75,9 @@ void vm_enable_npt(struct kvm_vm *vm)
pte_masks = vm->mmu.arch.pte_masks;
pte_masks.c = 0;
/* NPT walks are treated as user accesses, so set the 'user' bit. */
pte_masks.always_set = pte_masks.user;
tdp_mmu_init(vm, vm->mmu.pgtable_levels, &pte_masks);
}