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Commit 4ff41732 authored by Paolo Bonzini's avatar Paolo Bonzini
Browse files

KVM: x86: introduce kvm_supported_xcr0() 



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: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 94b3ffcd

arch/x86/kvm/cpuid.c

+16 −11
Original line number Diff line number Diff line
@@ -43,6 +43,16 @@ static u32 xstate_required_size(u64 xstate_bv) 
	return ret;

}



u64 kvm_supported_xcr0(void)

{

	u64 xcr0 = KVM_SUPPORTED_XCR0 & host_xcr0;



	if (!kvm_x86_ops->mpx_supported || !kvm_x86_ops->mpx_supported())

		xcr0 &= ~(XSTATE_BNDREGS | XSTATE_BNDCSR);



	return xcr0;

}



void kvm_update_cpuid(struct kvm_vcpu *vcpu)

{

	struct kvm_cpuid_entry2 *best;
@@ -73,7 +83,7 @@ void kvm_update_cpuid(struct kvm_vcpu *vcpu) 
	} else {

		vcpu->arch.guest_supported_xcr0 =

			(best->eax | ((u64)best->edx << 32)) &

			host_xcr0 & KVM_SUPPORTED_XCR0;

			kvm_supported_xcr0();

		vcpu->arch.guest_xstate_size = best->ebx =

			xstate_required_size(vcpu->arch.xcr0);

	}
@@ -210,13 +220,6 @@ static void do_cpuid_1_ent(struct kvm_cpuid_entry2 *entry, u32 function, 
	entry->flags = 0;

}



static bool supported_xcr0_bit(unsigned bit)

{

	u64 mask = ((u64)1 << bit);



	return mask & KVM_SUPPORTED_XCR0 & host_xcr0;

}



#define F(x) bit(X86_FEATURE_##x)



static int __do_cpuid_ent_emulated(struct kvm_cpuid_entry2 *entry,
@@ -439,16 +442,18 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function, 
	}

	case 0xd: {

		int idx, i;

		u64 supported = kvm_supported_xcr0();



		entry->eax &= host_xcr0 & KVM_SUPPORTED_XCR0;

		entry->edx &= (host_xcr0 & KVM_SUPPORTED_XCR0) >> 32;

		entry->eax &= supported;

		entry->edx &= supported >> 32;

		entry->flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX;

		for (idx = 1, i = 1; idx < 64; ++idx) {

			u64 mask = ((u64)1 << idx);

			if (*nent >= maxnent)

				goto out;



			do_cpuid_1_ent(&entry[i], function, idx);

			if (entry[i].eax == 0 || !supported_xcr0_bit(idx))

			if (entry[i].eax == 0 || !(supported & mask))

				continue;

			entry[i].flags |=

			       KVM_CPUID_FLAG_SIGNIFCANT_INDEX;

arch/x86/kvm/x86.c

+1 −3
Original line number Diff line number Diff line
@@ -3084,9 +3084,7 @@ static int kvm_vcpu_ioctl_x86_set_xsave(struct kvm_vcpu *vcpu, 
		 * CPUID leaf 0xD, index 0, EDX:EAX.  This is for compatibility

		 * with old userspace.

		 */

		if (xstate_bv & ~KVM_SUPPORTED_XCR0)

			return -EINVAL;

		if (xstate_bv & ~host_xcr0)

		if (xstate_bv & ~kvm_supported_xcr0())

			return -EINVAL;

		memcpy(&vcpu->arch.guest_fpu.state->xsave,

			guest_xsave->region, vcpu->arch.guest_xstate_size);

arch/x86/kvm/x86.h

+2 −0
Original line number Diff line number Diff line
@@ -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;