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kvm: x86: Use KVM CPU capabilities to determine CR4 reserved bits 

Using CPUID data can be useful for the processor compatibility
check, but that's it.  Using it to compute guest-reserved bits
can have both false positives (such as LA57 and UMIP which we
are already handling) and false negatives: in particular, with
this patch we don't allow anymore a KVM guest to set CR4.PKE
when CR4.PKE is clear on the host.

Fixes: b9dd21e104 ("KVM: x86: simplify handling of PKRU")
Reported-by: Jim Mattson <jmattson@google.com>
Tested-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2020-05-05 09:40:46 -04:00
parent c7cb2d650c
commit 139f7425fd
1 changed files with 5 additions and 15 deletions
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20
arch/x86/kvm/x86.c
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@ -926,19 +926,6 @@ EXPORT_SYMBOL_GPL(kvm_set_xcr);
__reserved_bits; \ __reserved_bits; \
}) })
static u64 kvm_host_cr4_reserved_bits(struct cpuinfo_x86 *c)
{
u64 reserved_bits = __cr4_reserved_bits(cpu_has, c);
if (kvm_cpu_cap_has(X86_FEATURE_LA57))
reserved_bits &= ~X86_CR4_LA57;
if (kvm_cpu_cap_has(X86_FEATURE_UMIP))
reserved_bits &= ~X86_CR4_UMIP;
return reserved_bits;
}
static int kvm_valid_cr4(struct kvm_vcpu *vcpu, unsigned long cr4) static int kvm_valid_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
{ {
if (cr4 & cr4_reserved_bits) if (cr4 & cr4_reserved_bits)
@ -9675,7 +9662,9 @@ int kvm_arch_hardware_setup(void *opaque)
if (!kvm_cpu_cap_has(X86_FEATURE_XSAVES)) if (!kvm_cpu_cap_has(X86_FEATURE_XSAVES))
supported_xss = 0; supported_xss = 0;
cr4_reserved_bits = kvm_host_cr4_reserved_bits(&boot_cpu_data); #define __kvm_cpu_cap_has(UNUSED_, f) kvm_cpu_cap_has(f)
cr4_reserved_bits = __cr4_reserved_bits(__kvm_cpu_cap_has, UNUSED_);
#undef __kvm_cpu_cap_has
if (kvm_has_tsc_control) { if (kvm_has_tsc_control) {
/* /*
@ -9707,7 +9696,8 @@ int kvm_arch_check_processor_compat(void *opaque)
WARN_ON(!irqs_disabled()); WARN_ON(!irqs_disabled());
if (kvm_host_cr4_reserved_bits(c) != cr4_reserved_bits) if (__cr4_reserved_bits(cpu_has, c) !=
__cr4_reserved_bits(cpu_has, &boot_cpu_data))
return -EIO; return -EIO;
return ops->check_processor_compatibility(); return ops->check_processor_compatibility();