linux-kernel - Re: [PATCH] LoongArch: KVM: Remove unnecessary CSR register saving during enter guest

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Message-ID: <b7c08e0d-bd7d-aea9-250e-1649e95599b7@loongson.cn>
Date: Wed, 31 Jan 2024 11:48:16 +0800
From: maobibo <maobibo@...ngson.cn>
To: Tianrui Zhao <zhaotianrui@...ngson.cn>,
 Huacai Chen <chenhuacai@...nel.org>
Cc: kvm@...r.kernel.org, loongarch@...ts.linux.dev,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] LoongArch: KVM: Remove unnecessary CSR register saving
 during enter guest

slightly ping :)

On 2024/1/12 上午11:50, Bibo Mao wrote:
> Some CSR registers like CRMD/PRMD are saved during enter VM mode. However
> they are not restored for actual use, saving for these CSR registers
> can be removed.
> 
> Signed-off-by: Bibo Mao <maobibo@...ngson.cn>
> ---
>   arch/loongarch/kvm/switch.S | 6 ------
>   1 file changed, 6 deletions(-)
> 
> diff --git a/arch/loongarch/kvm/switch.S b/arch/loongarch/kvm/switch.S
> index 0ed9040307b7..905b90de50e8 100644
> --- a/arch/loongarch/kvm/switch.S
> +++ b/arch/loongarch/kvm/switch.S
> @@ -213,12 +213,6 @@ SYM_FUNC_START(kvm_enter_guest)
>   	/* Save host GPRs */
>   	kvm_save_host_gpr a2
>   
> -	/* Save host CRMD, PRMD to stack */
> -	csrrd	a3, LOONGARCH_CSR_CRMD
> -	st.d	a3, a2, PT_CRMD
> -	csrrd	a3, LOONGARCH_CSR_PRMD
> -	st.d	a3, a2, PT_PRMD
> -
>   	addi.d	a2, a1, KVM_VCPU_ARCH
>   	st.d	sp, a2, KVM_ARCH_HSP
>   	st.d	tp, a2, KVM_ARCH_HTP
> 
> base-commit: de927f6c0b07d9e698416c5b287c521b07694cac
>