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Subject: Re: [PATCH] powerpc: fix 32-bit KVM-PR lockup and panic with MacOS
 guest
To:     Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>,
        benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au,
        npiggin@gmail.com, linuxppc-dev@lists.ozlabs.org,
        linux-kernel@vger.kernel.org, kvm-ppc@vger.kernel.org
References: <20190208143319.11980-1-mark.cave-ayland@ilande.co.uk>
From:   Christophe Leroy <christophe.leroy@c-s.fr>
Message-ID: <41b02fb0-cdc6-6de0-d8fc-44d3d0a8ad70@c-s.fr>
Date:   Fri, 8 Feb 2019 15:45:24 +0100
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Le 08/02/2019 à 15:33, Mark Cave-Ayland a écrit :
> Commit 8792468da5e1 "powerpc: Add the ability to save FPU without giving it up"

Expected format for the above is:

Commit 123456789abc ("text")

> 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@ilande.co.uk>

Should include a Fixes: and a Cc to stable ?

Fixes: 8792468da5e1 ("powerpc: Add the ability to save FPU without 
giving it up")
Cc: stable@vger.kernel.org

Christophe

> ---
>   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;
>