6.8-stable review patch. If anyone has any objections, please let me know.
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From: Josh Poimboeuf jpoimboe@kernel.org
commit cb2db5bb04d7f778fbc1a1ea2507aab436f1bff3 upstream.
There's no need to keep reading MSR_IA32_ARCH_CAPABILITIES over and over. It's even read in the BHI sysfs function which is a big no-no. Just read it once and cache it.
Fixes: ec9404e40e8f ("x86/bhi: Add BHI mitigation knob") Signed-off-by: Josh Poimboeuf jpoimboe@kernel.org Signed-off-by: Ingo Molnar mingo@kernel.org Reviewed-by: Nikolay Borisov nik.borisov@suse.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Sean Christopherson seanjc@google.com Link: https://lore.kernel.org/r/9592a18a814368e75f8f4b9d74d3883aa4fd1eaf.171281347... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kernel/cpu/bugs.c | 22 +++++++--------------- 1 file changed, 7 insertions(+), 15 deletions(-)
--- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -61,6 +61,8 @@ EXPORT_SYMBOL_GPL(x86_spec_ctrl_current) u64 x86_pred_cmd __ro_after_init = PRED_CMD_IBPB; EXPORT_SYMBOL_GPL(x86_pred_cmd);
+static u64 __ro_after_init ia32_cap; + static DEFINE_MUTEX(spec_ctrl_mutex);
void (*x86_return_thunk)(void) __ro_after_init = __x86_return_thunk; @@ -144,6 +146,8 @@ void __init cpu_select_mitigations(void) x86_spec_ctrl_base &= ~SPEC_CTRL_MITIGATIONS_MASK; }
+ ia32_cap = x86_read_arch_cap_msr(); + /* Select the proper CPU mitigations before patching alternatives: */ spectre_v1_select_mitigation(); spectre_v2_select_mitigation(); @@ -301,8 +305,6 @@ static const char * const taa_strings[]
static void __init taa_select_mitigation(void) { - u64 ia32_cap; - if (!boot_cpu_has_bug(X86_BUG_TAA)) { taa_mitigation = TAA_MITIGATION_OFF; return; @@ -341,7 +343,6 @@ static void __init taa_select_mitigation * On MDS_NO=1 CPUs if ARCH_CAP_TSX_CTRL_MSR is not set, microcode * update is required. */ - ia32_cap = x86_read_arch_cap_msr(); if ( (ia32_cap & ARCH_CAP_MDS_NO) && !(ia32_cap & ARCH_CAP_TSX_CTRL_MSR)) taa_mitigation = TAA_MITIGATION_UCODE_NEEDED; @@ -401,8 +402,6 @@ static const char * const mmio_strings[]
static void __init mmio_select_mitigation(void) { - u64 ia32_cap; - if (!boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA) || boot_cpu_has_bug(X86_BUG_MMIO_UNKNOWN) || cpu_mitigations_off()) { @@ -413,8 +412,6 @@ static void __init mmio_select_mitigatio if (mmio_mitigation == MMIO_MITIGATION_OFF) return;
- ia32_cap = x86_read_arch_cap_msr(); - /* * Enable CPU buffer clear mitigation for host and VMM, if also affected * by MDS or TAA. Otherwise, enable mitigation for VMM only. @@ -508,7 +505,7 @@ static void __init rfds_select_mitigatio if (rfds_mitigation == RFDS_MITIGATION_OFF) return;
- if (x86_read_arch_cap_msr() & ARCH_CAP_RFDS_CLEAR) + if (ia32_cap & ARCH_CAP_RFDS_CLEAR) setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF); else rfds_mitigation = RFDS_MITIGATION_UCODE_NEEDED; @@ -659,8 +656,6 @@ void update_srbds_msr(void)
static void __init srbds_select_mitigation(void) { - u64 ia32_cap; - if (!boot_cpu_has_bug(X86_BUG_SRBDS)) return;
@@ -669,7 +664,6 @@ static void __init srbds_select_mitigati * are only exposed to SRBDS when TSX is enabled or when CPU is affected * by Processor MMIO Stale Data vulnerability. */ - ia32_cap = x86_read_arch_cap_msr(); if ((ia32_cap & ARCH_CAP_MDS_NO) && !boot_cpu_has(X86_FEATURE_RTM) && !boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA)) srbds_mitigation = SRBDS_MITIGATION_TSX_OFF; @@ -813,7 +807,7 @@ static void __init gds_select_mitigation /* Will verify below that mitigation _can_ be disabled */
/* No microcode */ - if (!(x86_read_arch_cap_msr() & ARCH_CAP_GDS_CTRL)) { + if (!(ia32_cap & ARCH_CAP_GDS_CTRL)) { if (gds_mitigation == GDS_MITIGATION_FORCE) { /* * This only needs to be done on the boot CPU so do it @@ -1907,8 +1901,6 @@ static void update_indir_branch_cond(voi /* Update the static key controlling the MDS CPU buffer clear in idle */ static void update_mds_branch_idle(void) { - u64 ia32_cap = x86_read_arch_cap_msr(); - /* * Enable the idle clearing if SMT is active on CPUs which are * affected only by MSBDS and not any other MDS variant. @@ -2817,7 +2809,7 @@ static const char *spectre_bhi_state(voi else if (boot_cpu_has(X86_FEATURE_CLEAR_BHB_LOOP)) return "; BHI: SW loop, KVM: SW loop"; else if (boot_cpu_has(X86_FEATURE_RETPOLINE) && - !(x86_read_arch_cap_msr() & ARCH_CAP_RRSBA)) + !(ia32_cap & ARCH_CAP_RRSBA)) return "; BHI: Retpoline"; else if (boot_cpu_has(X86_FEATURE_CLEAR_BHB_LOOP_ON_VMEXIT)) return "; BHI: Syscall hardening, KVM: SW loop";