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Commit b39dc9a8 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Greg Kroah-Hartman
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x86/kvm/vmx: Add MDS protection when L1D Flush is not active 



commit 650b68a0622f933444a6d66936abb3103029413b upstream

CPUs which are affected by L1TF and MDS mitigate MDS with the L1D Flush on
VMENTER when updated microcode is installed.

If a CPU is not affected by L1TF or if the L1D Flush is not in use, then
MDS mitigation needs to be invoked explicitly.

For these cases, follow the host mitigation state and invoke the MDS
mitigation before VMENTER.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: default avatarFrederic Weisbecker <frederic@kernel.org>
Reviewed-by: default avatarBorislav Petkov <bp@suse.de>
Reviewed-by: default avatarJon Masters <jcm@redhat.com>
Tested-by: default avatarJon Masters <jcm@redhat.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent e4fa775b

arch/x86/kernel/cpu/bugs.c

+1 −0
Original line number Diff line number Diff line
@@ -63,6 +63,7 @@ DEFINE_STATIC_KEY_FALSE(switch_mm_always_ibpb); 


/* Control MDS CPU buffer clear before returning to user space */

DEFINE_STATIC_KEY_FALSE(mds_user_clear);

EXPORT_SYMBOL_GPL(mds_user_clear);



void __init check_bugs(void)

{

arch/x86/kvm/vmx.c

+3 −0
Original line number Diff line number Diff line
@@ -10765,8 +10765,11 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu) 
	evmcs_rsp = static_branch_unlikely(&enable_evmcs) ?

		(unsigned long)&current_evmcs->host_rsp : 0;



	/* L1D Flush includes CPU buffer clear to mitigate MDS */

	if (static_branch_unlikely(&vmx_l1d_should_flush))

		vmx_l1d_flush(vcpu);

	else if (static_branch_unlikely(&mds_user_clear))

		mds_clear_cpu_buffers();



	asm(

		/* Store host registers */