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72 lines
2.7 KiB
72 lines
2.7 KiB
1 year ago
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From 0d056d6da9e4147d5965bf3507f6d6d6a413924d Mon Sep 17 00:00:00 2001
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From: Emanuele Giuseppe Esposito <eesposit@redhat.com>
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Date: Wed, 24 May 2023 06:52:43 -0400
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Subject: [PATCH 2/5] target/i386: add support for FB_CLEAR feature
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RH-Author: Emanuele Giuseppe Esposito <eesposit@redhat.com>
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RH-MergeRequest: 167: target/i386: add support for FB_CLEAR feature
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RH-Bugzilla: 2216201
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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RH-Commit: [2/2] 5f191964ba25754107a06ef907f4ac614280aaa1 (eesposit/qemu-kvm)
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Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2216201
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commit 22e1094ca82d5518c1b69aff3e87c550776ae1eb
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Author: Emanuele Giuseppe Esposito <eesposit@redhat.com>
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Date: Wed Feb 1 08:57:59 2023 -0500
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target/i386: add support for FB_CLEAR feature
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As reported by the Intel's doc:
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"FB_CLEAR: The processor will overwrite fill buffer values as part of
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MD_CLEAR operations with the VERW instruction.
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On these processors, L1D_FLUSH does not overwrite fill buffer values."
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If this cpu feature is present in host, allow QEMU to choose whether to
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show it to the guest too.
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One disadvantage of not exposing it is that the guest will report
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a non existing vulnerability in
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/sys/devices/system/cpu/vulnerabilities/mmio_stale_data
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because the mitigation is present only when the cpu has
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(FLUSH_L1D and MD_CLEAR) or FB_CLEAR
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features enabled.
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Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
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Message-Id: <20230201135759.555607-3-eesposit@redhat.com>
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
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---
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target/i386/cpu.c | 2 +-
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target/i386/cpu.h | 1 +
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2 files changed, 2 insertions(+), 1 deletion(-)
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diff --git a/target/i386/cpu.c b/target/i386/cpu.c
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index caf6338cc0..839706b430 100644
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--- a/target/i386/cpu.c
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+++ b/target/i386/cpu.c
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@@ -1012,7 +1012,7 @@ FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
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"ssb-no", "mds-no", "pschange-mc-no", "tsx-ctrl",
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"taa-no", NULL, NULL, NULL,
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NULL, NULL, NULL, NULL,
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- NULL, NULL, NULL, NULL,
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+ NULL, "fb-clear", NULL, NULL,
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NULL, NULL, NULL, NULL,
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NULL, NULL, NULL, NULL,
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NULL, NULL, NULL, NULL,
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diff --git a/target/i386/cpu.h b/target/i386/cpu.h
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index 74fa649b60..c28b9df217 100644
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--- a/target/i386/cpu.h
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+++ b/target/i386/cpu.h
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@@ -989,6 +989,7 @@ uint64_t x86_cpu_get_supported_feature_word(FeatureWord w,
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#define MSR_ARCH_CAP_PSCHANGE_MC_NO (1U << 6)
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#define MSR_ARCH_CAP_TSX_CTRL_MSR (1U << 7)
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#define MSR_ARCH_CAP_TAA_NO (1U << 8)
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+#define MSR_ARCH_CAP_FB_CLEAR (1U << 17)
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#define MSR_CORE_CAP_SPLIT_LOCK_DETECT (1U << 5)
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--
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2.39.3
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