aboutsummaryrefslogtreecommitdiff
path: root/arch/x86
diff options
context:
space:
mode:
authorPawan Gupta2024-03-11 12:29:43 -0700
committerDave Hansen2024-03-11 13:13:28 -0700
commite95df4ec0c0c9791941f112db699fae794b9862a (patch)
tree273916b25df45c01c17612b7715a432f40444604 /arch/x86
parent90d35da658da8cff0d4ecbb5113f5fac9d00eb72 (diff)
x86/mmio: Disable KVM mitigation when X86_FEATURE_CLEAR_CPU_BUF is set
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>
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/kernel/cpu/bugs.c14
1 files changed, 12 insertions, 2 deletions
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 48d049cd74e7..cd6ac89c1a0d 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();
}