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

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Date: Mon, 26 Feb 2024 20:58:00 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: zhaotianrui <zhaotianrui@...ngson.cn>
Cc: maobibo <maobibo@...ngson.cn>, 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

LGTM, queued for loongarch-kvm.

Huacai

On Thu, Feb 1, 2024 at 11:30 AM zhaotianrui <zhaotianrui@...ngson.cn> wrote:
>
> Reviewed-by: Tianrui Zhao <zhaotianrui@...ngson.cn>
>
> 在 2024/1/31 上午11:48, maobibo 写道:
> > 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
> >>
>
>