pve-kernel-lowlatency-qoup/patches/kernel/0015-KVM-nSVM-Advertise-support-for-flush-by-ASID.patch
Stefan Sterz 7a0603cc5d backport exposing FLUSHBYASID when running nested VMs on AMD CPUs
this exposes the FLUSHBYASID CPU flag to nested VMs when running on an
AMD CPU. also reverts a made up check that would advertise
FLUSHBYASID as not supported. this enable certain modern hypervisors
such as VMWare ESXi 7 and Workstation 17 to run nested VMs properly
again.

Signed-off-by: Stefan Sterz <s.sterz@proxmox.com>
(cherry picked from commit 3202de9857)
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
2023-12-01 15:24:01 +01:00

40 lines
1.5 KiB
Diff

From 42af81abf0b96ab661591d024aed55c05dd85b91 Mon Sep 17 00:00:00 2001
From: Sean Christopherson <seanjc@google.com>
Date: Wed, 18 Oct 2023 12:41:04 -0700
Subject: [PATCH 2/2] 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>
---
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 9a194aa1a75a..0fde9b0c464b 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4880,6 +4880,7 @@ 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);
--
2.39.2