linux-kernel - Re: [PATCH 3/3] LoongArch: KVM: Set host with kernel mode when switch to VM mode

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Message-ID: <cc68705c-6900-f185-84b7-5473acb3ce96@loongson.cn>
Date: Mon, 10 Feb 2025 09:43:42 +0800
From: bibo mao <maobibo@...ngson.cn>
To: Huacai Chen <chenhuacai@...nel.org>
Cc: Tianrui Zhao <zhaotianrui@...ngson.cn>, WANG Xuerui <kernel@...0n.name>,
 kvm@...r.kernel.org, loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] LoongArch: KVM: Set host with kernel mode when switch
 to VM mode



On 2025/2/9 下午5:47, Huacai Chen wrote:
> Hi, Bibo,
> 
> On Fri, Feb 7, 2025 at 11:26 AM Bibo Mao <maobibo@...ngson.cn> wrote:
>>
>> PRMD and ERA register is only meaningful on the beginning stage
>> of exception entry, and it can be overwritten for nested irq or
>> exception.
> The code doesn't touch ERA, so ERA in the commit message is a typo?
oh, ERA is redundant here.
Will remove it in next version.

Regards
Bibo Mao
> 
> Huacai
>>
>> When CPU runs in VM mode, interrupt need be enabled on host. And the
>> mode for host had better be kernel mode rather than random.
>>
>> Signed-off-by: Bibo Mao <maobibo@...ngson.cn>
>> ---
>>   arch/loongarch/kvm/switch.S | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/loongarch/kvm/switch.S b/arch/loongarch/kvm/switch.S
>> index 0c292f818492..1be185e94807 100644
>> --- a/arch/loongarch/kvm/switch.S
>> +++ b/arch/loongarch/kvm/switch.S
>> @@ -85,7 +85,7 @@
>>           * Guest CRMD comes from separate GCSR_CRMD register
>>           */
>>          ori     t0, zero, CSR_PRMD_PIE
>> -       csrxchg t0, t0,   LOONGARCH_CSR_PRMD
>> +       csrwr   t0, LOONGARCH_CSR_PRMD
>>
>>          /* Set PVM bit to setup ertn to guest context */
>>          ori     t0, zero, CSR_GSTAT_PVM
>> --
>> 2.39.3
>>