pve-kernel-lowlatency-qoup/patches/kernel/0011-KVM-nSVM-Advertise-support-for-flush-by-ASID.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Sean Christopherson <seanjc@google.com>
Date: Wed, 18 Oct 2023 12:41:04 -0700
Subject: [PATCH] KVM: nSVM: Advertise support for flush-by-ASID

Advertise support for FLUSHBYASID when nested SVM is enabled, as KVM can
always emulate flushing TLB entries for a vmcb12 ASID, e.g. by running L2
with a new, fresh ASID in vmcb02.  Some modern hypervisors, e.g. VMWare
Workstation 17, require FLUSHBYASID support and will refuse to run if it's
not present.

Punt on proper support, as "Honor L1's request to flush an ASID on nested
VMRUN" is one of the TODO items in the (incomplete) list of issues that
need to be addressed in order for KVM to NOT do a full TLB flush on every
nested SVM transition (see nested_svm_transition_tlb_flush()).

Reported-by: Stefan Sterz <s.sterz@proxmox.com>
Closes: https://lkml.kernel.org/r/b9915c9c-4cf6-051a-2d91-44cc6380f455%40proxmox.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Stefan Sterz <s.sterz@proxmox.com>
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
---
 arch/x86/kvm/svm/svm.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index c8466bc64b87..6154eda73d41 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4983,6 +4983,7 @@ static __init void svm_set_cpu_caps(void)
 	if (nested) {
 		kvm_cpu_cap_set(X86_FEATURE_SVM);
 		kvm_cpu_cap_set(X86_FEATURE_VMCBCLEAN);
+		kvm_cpu_cap_set(X86_FEATURE_FLUSHBYASID);
 
 		if (nrips)
 			kvm_cpu_cap_set(X86_FEATURE_NRIPS);