Commit 139f7425 authored by Paolo Bonzini's avatar Paolo Bonzini
Browse files

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: b9dd21e1 ("KVM: x86: simplify handling of PKRU")
Reported-by: default avatarJim Mattson <jmattson@google.com>
Tested-by: default avatarJim Mattson <jmattson@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent c7cb2d65

arch/x86/kvm/x86.c

+5 −15
Original line number Diff line number Diff line
@@ -926,19 +926,6 @@ EXPORT_SYMBOL_GPL(kvm_set_xcr); 
	__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)

{

	if (cr4 & cr4_reserved_bits)
@@ -9675,7 +9662,9 @@ int kvm_arch_hardware_setup(void *opaque) 
	if (!kvm_cpu_cap_has(X86_FEATURE_XSAVES))

		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) {

		/*
@@ -9707,7 +9696,8 @@ int kvm_arch_check_processor_compat(void *opaque) 


	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 ops->check_processor_compatibility();

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