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| author | Pawan Gupta <pawan.kumar.gupta@linux.intel.com> | 2024-03-11 12:29:43 -0700 |
|---|---|---|
| committer | Sasha Levin <sashal@kernel.org> | 2024-03-15 10:48:21 -0400 |
| commit | c35ca0968de41952af2ad7d22881e4a7c6e1b145 (patch) | |
| tree | 743297e69027e4706c47c7587452dae44ffbeded | |
| parent | e2ee3c628a6f6d613ad96812036d61e36748a0b8 (diff) | |
| download | linux-c35ca0968de41952af2ad7d22881e4a7c6e1b145.tar.gz linux-c35ca0968de41952af2ad7d22881e4a7c6e1b145.tar.bz2 linux-c35ca0968de41952af2ad7d22881e4a7c6e1b145.zip | |
x86/mmio: Disable KVM mitigation when X86_FEATURE_CLEAR_CPU_BUF is set
commit e95df4ec0c0c9791941f112db699fae794b9862a upstream.
Currently MMIO Stale Data mitigation for CPUs not affected by MDS/TAA is
to only deploy VERW at VMentry by enabling mmio_stale_data_clear static
branch. No mitigation is needed for kernel->user transitions. If such
CPUs are also affected by RFDS, its mitigation may set
X86_FEATURE_CLEAR_CPU_BUF to deploy VERW at kernel->user and VMentry.
This could result in duplicate VERW at VMentry.
Fix this by disabling mmio_stale_data_clear static branch when
X86_FEATURE_CLEAR_CPU_BUF is enabled.
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | arch/x86/kernel/cpu/bugs.c | 14 |
1 files changed, 12 insertions, 2 deletions
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 17eb4d76e3a5..19256accc078 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -422,6 +422,13 @@ static void __init mmio_select_mitigation(void) if (boot_cpu_has_bug(X86_BUG_MDS) || (boot_cpu_has_bug(X86_BUG_TAA) && boot_cpu_has(X86_FEATURE_RTM))) setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF); + + /* + * X86_FEATURE_CLEAR_CPU_BUF could be enabled by other VERW based + * mitigations, disable KVM-only mitigation in that case. + */ + if (boot_cpu_has(X86_FEATURE_CLEAR_CPU_BUF)) + static_branch_disable(&mmio_stale_data_clear); else static_branch_enable(&mmio_stale_data_clear); @@ -498,8 +505,11 @@ static void __init md_clear_update_mitigation(void) taa_mitigation = TAA_MITIGATION_VERW; taa_select_mitigation(); } - if (mmio_mitigation == MMIO_MITIGATION_OFF && - boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA)) { + /* + * MMIO_MITIGATION_OFF is not checked here so that mmio_stale_data_clear + * gets updated correctly as per X86_FEATURE_CLEAR_CPU_BUF state. + */ + if (boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA)) { mmio_mitigation = MMIO_MITIGATION_VERW; mmio_select_mitigation(); } |