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KVM: x86: introduce kvm_supported_xcr0()

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XSAVE support for KVM is already using host_xcr0 & KVM_SUPPORTED_XCR0 as
a "dynamic" version of KVM_SUPPORTED_XCR0.

However, this is not enough because the MPX bits should not be presented
to the guest unless kvm_x86_ops confirms the support.  So, replace all
instances of host_xcr0 & KVM_SUPPORTED_XCR0 with a new function
kvm_supported_xcr0() that also has this check.

Note that here:

		if (xstate_bv & ~KVM_SUPPORTED_XCR0)
			return -EINVAL;
		if (xstate_bv & ~host_cr0)
			return -EINVAL;

the code is equivalent to

		if ((xstate_bv & ~KVM_SUPPORTED_XCR0) ||
		    (xstate_bv & ~host_cr0)
			return -EINVAL;

i.e. "xstate_bv & (~KVM_SUPPORTED_XCR0 | ~host_cr0)" which is in turn
equal to "xstate_bv & ~(KVM_SUPPORTED_XCR0 & host_cr0)".  So we should
also use the new function there.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini
2014-02-24 12:15:16 +01:00
parent 94b3ffcd41
commit 4ff417320c
3 changed files with 19 additions and 14 deletions
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2
arch/x86/kvm/x86.h
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@@ -126,6 +126,8 @@ int kvm_write_guest_virt_system(struct x86_emulate_ctxt *ctxt,
| XSTATE_BNDREGS | XSTATE_BNDCSR)
extern u64 host_xcr0;
extern u64 kvm_supported_xcr0(void);
extern unsigned int min_timer_period_us;
extern struct static_key kvm_no_apic_vcpu;