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[Qemu-devel] [PATCH] target-i386: fix losing XCR0 processor state compon


From: Wanpeng Li
Subject: [Qemu-devel] [PATCH] target-i386: fix losing XCR0 processor state component bits
Date: Wed, 28 Sep 2016 13:31:09 +0800

From: Wanpeng Li <address@hidden>

Commit 96193c22a "target-i386: Move xsave component mask to features array"
leverages features array to handle XCR0 processor state component bits, 
however, it introduces a regression:

warning: host doesn't support requested feature: CPUID.0DH:EAX [bit 0]
warning: host doesn't support requested feature: CPUID.0DH:EAX [bit 1]
warning: host doesn't support requested feature: CPUID.0DH:EAX [bit 2]

My desktop doesn't have enough advance features, so just X87,SSE,AVX 
warnings are splat when I boot a guest.

The get migratable flags logic in x86_cpu_filter_features() path will 
filter out the feature flags which are unsupported and unmigratable. 
However, the bits of XCR0 processor state component featureword don't 
have feat_names, and some features like SSE/AVX etc have feat_names in 
CPUID.01H:EDX, CPUID.01H:ECX, so they are treated as unsupported.

This patch fix it by don't filter out XCR0 processor state components 
bits though they don't have feat_names just as before commit 96193c22ab3.

Cc: Paolo Bonzini <address@hidden>
Cc: Richard Henderson <address@hidden>
Cc: Eduardo Habkost <address@hidden>
Cc: Michael S. Tsirkin <address@hidden>
Signed-off-by: Wanpeng Li <address@hidden>
---
 target-i386/cpu.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/target-i386/cpu.c b/target-i386/cpu.c
index ad09246..9d24eff 100644
--- a/target-i386/cpu.c
+++ b/target-i386/cpu.c
@@ -2156,6 +2156,10 @@ static uint32_t 
x86_cpu_get_supported_feature_word(FeatureWord w,
         r = kvm_arch_get_supported_cpuid(kvm_state, wi->cpuid_eax,
                                                     wi->cpuid_ecx,
                                                     wi->cpuid_reg);
+        if ((w == FEAT_XSAVE_COMP_LO) ||
+            (w == FEAT_XSAVE_COMP_HI)) {
+            return r;
+        }
     } else if (tcg_enabled()) {
         r = wi->tcg_features;
     } else {
-- 
1.9.1




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