63 lines
2.3 KiB
Diff
63 lines
2.3 KiB
Diff
From fb84b9baa665ffa4596fd871537e0544d60e40fc Mon Sep 17 00:00:00 2001
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From: Emanuele Giuseppe Esposito <eesposit@redhat.com>
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Date: Wed, 1 Feb 2023 08:57:59 -0500
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Subject: [PATCH] target/i386: add support for FB_CLEAR feature
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commit 22e1094ca82d5518c1b69aff3e87c550776ae1eb upstream.
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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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Intel-SIG: commit 22e1094ca82d ("target/i386: add support for FB_CLEAR feature")
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Backport support for FB_CLEAR feature
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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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[ jason: amend commit log ]
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Signed-off-by: Jason Zeng <jason.zeng@intel.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 512bec3ca3..8adc84b7f9 100644
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--- a/target/i386/cpu.c
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+++ b/target/i386/cpu.c
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@@ -982,7 +982,7 @@ 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 9e094ef934..d9aac5acd2 100644
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--- a/target/i386/cpu.h
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+++ b/target/i386/cpu.h
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@@ -962,6 +962,7 @@ 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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2.41.0.windows.1
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