[PATCH 4.12 35/99] KVM, pkeys: do not use PKRU value in vcpu->arch.guest_fpu.state

Greg Kroah-Hartman
2017-08-28T08:08:51Z

From: Paolo Bonzini <pbonzini@redhat.com>

commit 38cfd5e3df9c4f88e76b547eee2087ee5c042ae2 upstream.

The host pkru is restored right after vcpu exit (commit 1be0e61), so
KVM_GET_XSAVE will return the host PKRU value instead. Fix this by
using the guest PKRU explicitly in fill_xsave and load_xsave. This
part is based on a patch by Junkang Fu.

The host PKRU data may also not match the value in vcpu->arch.guest_fpu.state,
because it could have been changed by userspace since the last time
it was saved, so skip loading it in kvm_load_guest_fpu.

Reported-by: Junkang Fu <junkang.fjk@alibaba-inc.com>
Cc: Yang Zhang <zy107165@alibaba-inc.com>
Fixes: 1be0e61c1f255faaeab04a390e00c8b9b9042870
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/include/asm/fpu/internal.h | 6 +++---
arch/x86/kvm/x86.c | 17 ++++++++++++++---
2 files changed, 17 insertions(+), 6 deletions(-)

--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -450,10 +450,10 @@ static inline int copy_fpregs_to_fpstate
return 0;
}

-static inline void __copy_kernel_to_fpregs(union fpregs_state *fpstate)
+static inline void __copy_kernel_to_fpregs(union fpregs_state *fpstate, u64 mask)
{
if (use_xsave()) {
- copy_kernel_to_xregs(&fpstate->xsave, -1);
+ copy_kernel_to_xregs(&fpstate->xsave, mask);
} else {
if (use_fxsr())
copy_kernel_to_fxregs(&fpstate->fxsave);
@@ -477,7 +477,7 @@ static inline void copy_kernel_to_fpregs
: : [addr] "m" (fpstate));
}

- __copy_kernel_to_fpregs(fpstate);
+ __copy_kernel_to_fpregs(fpstate, -1);
}

extern int copy_fpstate_to_sigframe(void __user *buf, void __user *fp, int size);
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3236,7 +3236,12 @@ static void fill_xsave(u8 *dest, struct
u32 size, offset, ecx, edx;
cpuid_count(XSTATE_CPUID, index,
&size, &offset, &ecx, &edx);
- memcpy(dest + offset, src, size);
+ if (feature == XFEATURE_MASK_PKRU)
+ memcpy(dest + offset, &vcpu->arch.pkru,
+ sizeof(vcpu->arch.pkru));
+ else
+ memcpy(dest + offset, src, size);
+
}

valid -= feature;
@@ -3274,7 +3279,11 @@ static void load_xsave(struct kvm_vcpu *
u32 size, offset, ecx, edx;
cpuid_count(XSTATE_CPUID, index,
&size, &offset, &ecx, &edx);
- memcpy(dest, src + offset, size);
+ if (feature == XFEATURE_MASK_PKRU)
+ memcpy(&vcpu->arch.pkru, src + offset,
+ sizeof(vcpu->arch.pkru));
+ else
+ memcpy(dest, src + offset, size);
}

valid -= feature;
@@ -7616,7 +7625,9 @@ void kvm_load_guest_fpu(struct kvm_vcpu
*/
vcpu->guest_fpu_loaded = 1;
__kernel_fpu_begin();
- __copy_kernel_to_fpregs(&vcpu->arch.guest_fpu.state);
+ /* PKRU is separately restored in kvm_x86_ops->run. */
+ __copy_kernel_to_fpregs(&vcpu->arch.guest_fpu.state,
+ ~XFEATURE_MASK_PKRU);
trace_kvm_fpu(1);
}