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kvm: mmu: don't set the present bit unconditionally

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To support execute only mappings on behalf of L1
hypervisors, we need to teach set_spte() to honor all three of
L1's XWR bits.  As a start, add a new variable "shadow_present_mask"
that will be set for non-EPT shadow paging and clear for EPT.

Signed-off-by: Bandan Das <bsd@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Bandan Das
2016-07-12 18:18:49 -04:00
committed by Paolo Bonzini
parent 812f30b234
commit ffb128c89b
4 changed files with 11 additions and 9 deletions
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13
arch/x86/kvm/mmu.c
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@@ -175,6 +175,7 @@ static u64 __read_mostly shadow_user_mask;
static u64 __read_mostly shadow_accessed_mask;
static u64 __read_mostly shadow_dirty_mask;
static u64 __read_mostly shadow_mmio_mask;
static u64 __read_mostly shadow_present_mask;
static void mmu_spte_set(u64 *sptep, u64 spte);
static void mmu_free_roots(struct kvm_vcpu *vcpu);
@@ -282,13 +283,14 @@ static bool check_mmio_spte(struct kvm_vcpu *vcpu, u64 spte)
}
void kvm_mmu_set_mask_ptes(u64 user_mask, u64 accessed_mask,
u64 dirty_mask, u64 nx_mask, u64 x_mask)
u64 dirty_mask, u64 nx_mask, u64 x_mask, u64 p_mask)
{
shadow_user_mask = user_mask;
shadow_accessed_mask = accessed_mask;
shadow_dirty_mask = dirty_mask;
shadow_nx_mask = nx_mask;
shadow_x_mask = x_mask;
shadow_present_mask = p_mask;
}
EXPORT_SYMBOL_GPL(kvm_mmu_set_mask_ptes);
@@ -2245,10 +2247,9 @@ static void link_shadow_page(struct kvm_vcpu *vcpu, u64 *sptep,
{
u64 spte;
BUILD_BUG_ON(VMX_EPT_READABLE_MASK != PT_PRESENT_MASK ||
VMX_EPT_WRITABLE_MASK != PT_WRITABLE_MASK);
BUILD_BUG_ON(VMX_EPT_WRITABLE_MASK != PT_WRITABLE_MASK);
spte = __pa(sp->spt) | PT_PRESENT_MASK | PT_WRITABLE_MASK |
spte = __pa(sp->spt) | shadow_present_mask | PT_WRITABLE_MASK |
shadow_user_mask | shadow_x_mask | shadow_accessed_mask;
mmu_spte_set(sptep, spte);
@@ -2515,13 +2516,13 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
gfn_t gfn, kvm_pfn_t pfn, bool speculative,
bool can_unsync, bool host_writable)
{
u64 spte;
u64 spte = 0;
int ret = 0;
if (set_mmio_spte(vcpu, sptep, gfn, pfn, pte_access))
return 0;
spte = PT_PRESENT_MASK;
spte |= shadow_present_mask;
if (!speculative)
spte |= shadow_accessed_mask;