2018-02-23 02:52:34 +01:00
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From 4e5e2c853977dc27ddab5937e55d181e7f1b5d2a Mon Sep 17 00:00:00 2001
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2018-02-22 23:01:24 +01:00
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From: Bruce Rogers <brogers@suse.com>
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Date: Thu, 22 Feb 2018 04:48:07 -0700
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Subject: [PATCH] i386: Compensate for KVM SPEC_CTRL feature availability bug
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As we move away from the quick and dirty qemu solution for
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Spectre v2, it was found that KVM wasn't reporting the SPEC_CTRL
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feature when it in fact was present due to microcode update.
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This patch compensates for that bug by checking for the feature
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in QEMU code (like the quick and dirty solution did), instead of
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simply relying on KVM for that information.
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[BR: BSC#1082276]
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Signed-off-by: Bruce Rogers <brogers@suse.com>
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---
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target/i386/cpu.c | 8 ++++++++
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1 file changed, 8 insertions(+)
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diff --git a/target/i386/cpu.c b/target/i386/cpu.c
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index a7e27f3bbf..5c34175f3f 100644
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--- a/target/i386/cpu.c
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+++ b/target/i386/cpu.c
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@@ -2824,6 +2824,14 @@ static uint32_t x86_cpu_get_supported_feature_word(FeatureWord w,
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r = kvm_arch_get_supported_cpuid(kvm_state, wi->cpuid_eax,
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wi->cpuid_ecx,
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wi->cpuid_reg);
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+ // BUG!!! We need to compensate for a KVM bug where it doesn't
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+ // correctly report support for IBRS (bsc#1082276)
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+ if (w == FEAT_7_0_EDX) {
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+ uint32_t edx;
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+ host_cpuid(7, 0, NULL, NULL, NULL, &edx);
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+#define CPUID_7_0_EDX_PRED_CMD (1U << 27)
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+ r |= edx & (CPUID_7_0_EDX_SPEC_CTRL | CPUID_7_0_EDX_PRED_CMD);
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+ }
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} else if (tcg_enabled()) {
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r = wi->tcg_features;
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} else {
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