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x86/bugs: Rename mmio_stale_data_clear to cpu_buf_vm_clear

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The static key mmio_stale_data_clear controls the KVM-only mitigation for MMIO
Stale Data vulnerability. Rename it to reflect its purpose.

No functional change.

Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250416-mmio-rename-v2-1-ad1f5488767c@linux.intel.com
This commit is contained in:
Pawan Gupta
2025-04-16 06:47:51 -07:00
committed by Borislav Petkov (AMD)
parent 8ffd015db8
commit d9b79111fd
3 changed files with 16 additions and 8 deletions
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2
arch/x86/include/asm/nospec-branch.h
View File

@@ -561,7 +561,7 @@ DECLARE_STATIC_KEY_FALSE(mds_idle_clear);
DECLARE_STATIC_KEY_FALSE(switch_mm_cond_l1d_flush);
DECLARE_STATIC_KEY_FALSE(mmio_stale_data_clear);
DECLARE_STATIC_KEY_FALSE(cpu_buf_vm_clear);
extern u16 mds_verw_sel;

16
arch/x86/kernel/cpu/bugs.c
View File

@@ -127,9 +127,13 @@ EXPORT_SYMBOL_GPL(mds_idle_clear);
*/
DEFINE_STATIC_KEY_FALSE(switch_mm_cond_l1d_flush);
/* Controls CPU Fill buffer clear before KVM guest MMIO accesses */
DEFINE_STATIC_KEY_FALSE(mmio_stale_data_clear);
EXPORT_SYMBOL_GPL(mmio_stale_data_clear);
/*
* Controls CPU Fill buffer clear before VMenter. This is a subset of
* X86_FEATURE_CLEAR_CPU_BUF, and should only be enabled when KVM-only
* mitigation is required.
*/
DEFINE_STATIC_KEY_FALSE(cpu_buf_vm_clear);
EXPORT_SYMBOL_GPL(cpu_buf_vm_clear);
void __init cpu_select_mitigations(void)
{
@@ -449,9 +453,9 @@ static void __init mmio_select_mitigation(void)
* mitigations, disable KVM-only mitigation in that case.
*/
if (boot_cpu_has(X86_FEATURE_CLEAR_CPU_BUF))
static_branch_disable(&mmio_stale_data_clear);
static_branch_disable(&cpu_buf_vm_clear);
else
static_branch_enable(&mmio_stale_data_clear);
static_branch_enable(&cpu_buf_vm_clear);
/*
* If Processor-MMIO-Stale-Data bug is present and Fill Buffer data can
@@ -571,7 +575,7 @@ static void __init md_clear_update_mitigation(void)
taa_select_mitigation();
}
/*
* MMIO_MITIGATION_OFF is not checked here so that mmio_stale_data_clear
* MMIO_MITIGATION_OFF is not checked here so that cpu_buf_vm_clear
* gets updated correctly as per X86_FEATURE_CLEAR_CPU_BUF state.
*/
if (boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA)) {

6
arch/x86/kvm/vmx/vmx.c
View File

@@ -7358,10 +7358,14 @@ static noinstr void vmx_vcpu_enter_exit(struct kvm_vcpu *vcpu,
* mitigation for MDS is done late in VMentry and is still
* executed in spite of L1D Flush. This is because an extra VERW
* should not matter much after the big hammer L1D Flush.
*
* cpu_buf_vm_clear is used when system is not vulnerable to MDS/TAA,
* and is affected by MMIO Stale Data. In such cases mitigation in only
* needed against an MMIO capable guest.
*/
if (static_branch_unlikely(&vmx_l1d_should_flush))
vmx_l1d_flush(vcpu);
else if (static_branch_unlikely(&mmio_stale_data_clear) &&
else if (static_branch_unlikely(&cpu_buf_vm_clear) &&
kvm_arch_has_assigned_device(vcpu->kvm))
mds_clear_cpu_buffers();