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KVM: x86: use correct page table format to check nested page table reserved bits 

Intel CPUID on AMD host or vice versa is a weird case, but it can
happen.  Handle it by checking the host CPU vendor instead of the
guest's in reset_tdp_shadow_zero_bits_mask.  For speed, the
check uses the fact that Intel EPT has an X (executable) bit while
AMD NPT has NX.

Reported-by: Borislav Petkov <bp@alien8.de>
Tested-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2015-09-22 23:02:14 +02:00
parent 79a8059d24
commit 6fec21449a
1 changed files with 17 additions and 6 deletions
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23
arch/x86/kvm/mmu.c
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@ -3614,7 +3614,7 @@ static void
__reset_rsvds_bits_mask(struct kvm_vcpu *vcpu,
struct rsvd_bits_validate *rsvd_check,
int maxphyaddr, int level, bool nx, bool gbpages,
bool pse)
bool pse, bool amd)
{
u64 exb_bit_rsvd = 0;
u64 gbpages_bit_rsvd = 0;
@ -3631,7 +3631,7 @@ __reset_rsvds_bits_mask(struct kvm_vcpu *vcpu,
* Non-leaf PML4Es and PDPEs reserve bit 8 (which would be the G bit for
* leaf entries) on AMD CPUs only.
*/
if (guest_cpuid_is_amd(vcpu))
if (amd)
nonleaf_bit8_rsvd = rsvd_bits(8, 8);
switch (level) {
@ -3699,7 +3699,7 @@ static void reset_rsvds_bits_mask(struct kvm_vcpu *vcpu,
__reset_rsvds_bits_mask(vcpu, &context->guest_rsvd_check,
cpuid_maxphyaddr(vcpu), context->root_level,
context->nx, guest_cpuid_has_gbpages(vcpu),
is_pse(vcpu));
is_pse(vcpu), guest_cpuid_is_amd(vcpu));
}
static void
@ -3749,13 +3749,24 @@ static void reset_rsvds_bits_mask_ept(struct kvm_vcpu *vcpu,
void
reset_shadow_zero_bits_mask(struct kvm_vcpu *vcpu, struct kvm_mmu *context)
{
/*
* Passing "true" to the last argument is okay; it adds a check
* on bit 8 of the SPTEs which KVM doesn't use anyway.
*/
__reset_rsvds_bits_mask(vcpu, &context->shadow_zero_check,
boot_cpu_data.x86_phys_bits,
context->shadow_root_level, context->nx,
guest_cpuid_has_gbpages(vcpu), is_pse(vcpu));
guest_cpuid_has_gbpages(vcpu), is_pse(vcpu),
true);
}
EXPORT_SYMBOL_GPL(reset_shadow_zero_bits_mask);
static inline bool boot_cpu_is_amd(void)
{
WARN_ON_ONCE(!tdp_enabled);
return shadow_x_mask == 0;
}
/*
* the direct page table on host, use as much mmu features as
* possible, however, kvm currently does not do execution-protection.
@ -3764,11 +3775,11 @@ static void
reset_tdp_shadow_zero_bits_mask(struct kvm_vcpu *vcpu,
struct kvm_mmu *context)
{
if (guest_cpuid_is_amd(vcpu))
if (boot_cpu_is_amd())
__reset_rsvds_bits_mask(vcpu, &context->shadow_zero_check,
boot_cpu_data.x86_phys_bits,
context->shadow_root_level, false,
cpu_has_gbpages, true);
cpu_has_gbpages, true, true);
else
__reset_rsvds_bits_mask_ept(&context->shadow_zero_check,
boot_cpu_data.x86_phys_bits,