From 412a3c411e6df54179f300e8d8d6247327865a2d Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Wed, 3 Dec 2014 14:38:01 +0100
Subject: [PATCH] KVM: cpuid: set CPUID(EAX=0xd,ECX=1).EBX correctly
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This is the size of the XSAVES area. This starts providing guest support
for XSAVES (with no support yet for supervisor states, i.e. XSS == 0
always in guests for now).
Wanpeng Li suggested testing XSAVEC as well as XSAVES, since in practice
no real processor exists that only has one of them, and there is no
other way for userspace programs to compute the area of the XSAVEC
save area. CPUID(EAX=0xd,ECX=1).EBX provides an upper bound.
Suggested-by: Radim KrÄmáŠ<rkrcmar@redhat.com>
Reviewed-by: Radim KrÄmáŠ<rkrcmar@redhat.com>
Tested-by: Wanpeng Li <wanpeng.li@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/kvm/cpuid.c | 22 ++++++++++++++++------
1 file changed, 16 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index e24df01ab1180..2f7bc2de99150 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -23,7 +23,7 @@
#include "mmu.h"
#include "trace.h"
-static u32 xstate_required_size(u64 xstate_bv)
+static u32 xstate_required_size(u64 xstate_bv, bool compacted)
{
int feature_bit = 0;
u32 ret = XSAVE_HDR_SIZE + XSAVE_HDR_OFFSET;
@@ -31,9 +31,10 @@ static u32 xstate_required_size(u64 xstate_bv)
xstate_bv &= XSTATE_EXTEND_MASK;
while (xstate_bv) {
if (xstate_bv & 0x1) {
- u32 eax, ebx, ecx, edx;
+ u32 eax, ebx, ecx, edx, offset;
cpuid_count(0xD, feature_bit, &eax, &ebx, &ecx, &edx);
- ret = max(ret, eax + ebx);
+ offset = compacted ? ret : ebx;
+ ret = max(ret, offset + eax);
}
xstate_bv >>= 1;
@@ -87,9 +88,13 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu)
(best->eax | ((u64)best->edx << 32)) &
kvm_supported_xcr0();
vcpu->arch.guest_xstate_size = best->ebx =
- xstate_required_size(vcpu->arch.xcr0);
+ xstate_required_size(vcpu->arch.xcr0, false);
}
+ best = kvm_find_cpuid_entry(vcpu, 0xD, 1);
+ if (best && (best->eax & (F(XSAVES) | F(XSAVEC))))
+ best->ebx = xstate_required_size(vcpu->arch.xcr0, true);
+
/*
* The existing code assumes virtual address is 48-bit in the canonical
* address checks; exit if it is ever changed.
@@ -470,9 +475,14 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
goto out;
do_cpuid_1_ent(&entry[i], function, idx);
- if (idx == 1)
+ if (idx == 1) {
entry[i].eax &= kvm_supported_word10_x86_features;
- else if (entry[i].eax == 0 || !(supported & mask))
+ entry[i].ebx = 0;
+ if (entry[i].eax & (F(XSAVES)|F(XSAVEC)))
+ entry[i].ebx =
+ xstate_required_size(supported,
+ true);
+ } else if (entry[i].eax == 0 || !(supported & mask))
continue;
entry[i].flags |=
KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
--
2.30.2