linux-kernel - Re: [PATCH] KVM: Loongarch: Remove undefined a6 argument comment for kvm

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Message-ID: <CAAhV-H7Op_W0B7d4uQQVU_BEkpyQmwf9TCxQA9bYx3=JrQZ8pg@mail.gmail.com>
Date: Fri, 26 Jul 2024 14:32:24 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: maobibo <maobibo@...ngson.cn>
Cc: Dandan Zhang <zhangdandan@...ontech.com>, zhaotianrui@...ngson.cn, kernel@...0n.name, 
	kvm@...r.kernel.org, loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org, 
	wangyuli@...ontech.com, Wentao Guan <guanwentao@...ontech.com>
Subject: Re: [PATCH] KVM: Loongarch: Remove undefined a6 argument comment for kvm_hypercall

On Fri, Jul 26, 2024 at 11:35 AM maobibo <maobibo@...ngson.cn> wrote:
>
>
>
> On 2024/7/26 上午10:55, Huacai Chen wrote:
> > On Fri, Jul 26, 2024 at 9:49 AM maobibo <maobibo@...ngson.cn> wrote:
> >>
> >>
> >>
> >> On 2024/7/25 下午9:48, Dandan Zhang wrote:
> >>> The kvm_hypercall set for LoongArch is limited to a1-a5.
> >>> The mention of a6 in the comment is undefined that needs to be rectified.
> >>>
> >>> Signed-off-by: Wentao Guan <guanwentao@...ontech.com>
> >>> Signed-off-by: Dandan Zhang <zhangdandan@...ontech.com>
> >>> ---
> >>>    arch/loongarch/include/asm/kvm_para.h | 4 ++--
> >>>    1 file changed, 2 insertions(+), 2 deletions(-)
> >>>
> >>> diff --git a/arch/loongarch/include/asm/kvm_para.h b/arch/loongarch/include/asm/kvm_para.h
> >>> index 335fb86778e2..43ec61589e6c 100644
> >>> --- a/arch/loongarch/include/asm/kvm_para.h
> >>> +++ b/arch/loongarch/include/asm/kvm_para.h
> >>> @@ -39,9 +39,9 @@ struct kvm_steal_time {
> >>>     * Hypercall interface for KVM hypervisor
> >>>     *
> >>>     * a0: function identifier
> >>> - * a1-a6: args
> >>> + * a1-a5: args
> >>>     * Return value will be placed in a0.
> >>> - * Up to 6 arguments are passed in a1, a2, a3, a4, a5, a6.
> >>> + * Up to 5 arguments are passed in a1, a2, a3, a4, a5.
> >>>     */
> >>>    static __always_inline long kvm_hypercall0(u64 fid)
> >>>    {
> >>>
> >>
> >> Dandan,
> >>
> >> Nice catch. In future hypercall abi may expand such as the number of
> >> input register and output register, or async hypercall function if there
> >> is really such requirement.
> >>
> >> Anyway the modification is deserved and it is enough to use now, thanks
> >> for doing it.
> >>
> >> Reviewed-by: Bibo Mao <maobibo@...ngson.cn>
> > Maybe it is better to implement kvm_hypercall6() than remove a6 now?
> That is one option also. The main reason is that there is no such
> requirement in near future :(, I prefer to removing the annotation and
> keeping it clean.
I don't like removing something and then adding it back again, so if
kvm_hypercall6() is needed in future, it is better to add it now.

Huacai
>
> Regards
> Bibo Mao
> >
> > Huacai
> >>
>
>