Commit d9b79111 authored by Pawan Gupta's avatar Pawan Gupta Committed by Borislav Petkov (AMD)
Browse files

x86/bugs: Rename mmio_stale_data_clear to cpu_buf_vm_clear 



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: default avatarPawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250416-mmio-rename-v2-1-ad1f5488767c@linux.intel.com
parent 8ffd015d

arch/x86/include/asm/nospec-branch.h

+1 −1
Original line number Diff line number Diff line
@@ -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;

arch/x86/kernel/cpu/bugs.c

+10 −6
Original line number Diff line number Diff line
@@ -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)) {

arch/x86/kvm/vmx/vmx.c

+5 −1
Original line number Diff line number Diff line
@@ -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();