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x86/kvm/vmx: Add MDS protection when L1D Flush is not active

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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: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Jon Masters <jcm@redhat.com>
Tested-by: Jon Masters <jcm@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Thomas Gleixner 2019-02-27 12:48:14 +01:00 committed by Greg Kroah-Hartman
parent bfa08d23f9
commit 787311ce7f
2 changed files with 4 additions and 0 deletions
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1
arch/x86/kernel/cpu/bugs.c
View File

@ -62,6 +62,7 @@ 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)
{

3
arch/x86/kvm/vmx.c
View File

@ -9766,8 +9766,11 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
vmx->__launched = vmx->loaded_vmcs->launched;
/* 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 */