linux-kernel - [PATCH] powerpc: fix 32-bit KVM-PR lockup and panic with MacOS guest

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Message-Id: <20190208143319.11980-1-mark.cave-ayland@ilande.co.uk>
Date:   Fri,  8 Feb 2019 14:33:19 +0000
From:   Mark Cave-Ayland <mark.cave-ayland@...nde.co.uk>
To:     benh@...nel.crashing.org, paulus@...ba.org, mpe@...erman.id.au,
        npiggin@...il.com, christophe.leroy@....fr,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        kvm-ppc@...r.kernel.org
Subject: [PATCH] powerpc: fix 32-bit KVM-PR lockup and panic with MacOS guest

Commit 8792468da5e1 "powerpc: Add the ability to save FPU without giving it up"
unexpectedly removed the MSR_FE0 and MSR_FE1 bits from the bitmask used to
update the MSR of the previous thread in __giveup_fpu() causing a KVM-PR MacOS
guest to lockup and panic the kernel.

Reinstate these bits to the MSR bitmask to enable MacOS guests to run under
32-bit KVM-PR once again without issue.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@...nde.co.uk>
---
 arch/powerpc/kernel/process.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index ce393df243aa..71bad4b6f80d 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -176,7 +176,7 @@ static void __giveup_fpu(struct task_struct *tsk)
 
 	save_fpu(tsk);
 	msr = tsk->thread.regs->msr;
-	msr &= ~MSR_FP;
+	msr &= ~(MSR_FP|MSR_FE0|MSR_FE1);
 #ifdef CONFIG_VSX
 	if (cpu_has_feature(CPU_FTR_VSX))
 		msr &= ~MSR_VSX;
-- 
2.11.0