This is a note to let you know that I've just added the patch titled
KVM: PPC: Book3S HV: Fix KVM_RUN clobbering FP/VEC user registers
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kvm-ppc-book3s-hv-fix-kvm_run-clobbering-fp-vec-user-registers.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From dc158d23b33df9033bcc8e7117e8591dd2f9d125 Mon Sep 17 00:00:00 2001
From: Nicholas Piggin <npiggin@xxxxxxxxx>
Date: Wed, 22 Nov 2023 12:58:11 +1000
Subject: KVM: PPC: Book3S HV: Fix KVM_RUN clobbering FP/VEC user registers
From: Nicholas Piggin <npiggin@xxxxxxxxx>
commit dc158d23b33df9033bcc8e7117e8591dd2f9d125 upstream.
Before running a guest, the host process (e.g., QEMU) FP/VEC registers
are saved if they were being used, similarly to when the kernel uses FP
registers. The guest values are then loaded into regs, and the host
process registers will be restored lazily when it uses FP/VEC.
KVM HV has a bug here: the host process registers do get saved, but the
user MSR bits remain enabled, which indicates the registers are valid
for the process. After they are clobbered by running the guest, this
valid indication causes the host process to take on the FP/VEC register
values of the guest.
Fixes: 34e119c96b2b ("KVM: PPC: Book3S HV P9: Reduce mtmsrd instructions required to save host SPRs")
Cc: stable@xxxxxxxxxxxxxxx # v5.17+
Signed-off-by: Nicholas Piggin <npiggin@xxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Link: https://msgid.link/20231122025811.2973-1-npiggin@xxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/powerpc/kernel/process.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1198,11 +1198,11 @@ void kvmppc_save_user_regs(void)
usermsr = current->thread.regs->msr;
+ /* Caller has enabled FP/VEC/VSX/TM in MSR */
if (usermsr & MSR_FP)
- save_fpu(current);
-
+ __giveup_fpu(current);
if (usermsr & MSR_VEC)
- save_altivec(current);
+ __giveup_altivec(current);
#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
if (usermsr & MSR_TM) {
Patches currently in stable-queue which might be from npiggin@xxxxxxxxx are
queue-6.6/kvm-ppc-book3s-hv-fix-kvm_run-clobbering-fp-vec-user-registers.patch
