linux-kernel - Re: [PATCH v2] riscv: KVM: Remove unnecessary vcpu kick

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Message-ID: <CAAhSdy34iNEqcVOziJcjnhS5xTYx3o+iXex8bEAwmUDApXWAcg@mail.gmail.com>
Date: Fri, 21 Feb 2025 22:36:25 +0530
From: Anup Patel <anup@...infault.org>
To: BillXiang <xiangwencheng@...xincomputing.com>
Cc: ajones@...tanamicro.com, kvm-riscv@...ts.infradead.org, 
	kvm@...r.kernel.org, linux-riscv@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, atishp@...shpatra.org, paul.walmsley@...ive.com, 
	palmer@...belt.com, aou@...s.berkeley.edu, rkrcmar@...tanamicro.com
Subject: Re: [PATCH v2] riscv: KVM: Remove unnecessary vcpu kick

On Fri, Feb 21, 2025 at 4:16 PM BillXiang
<xiangwencheng@...xincomputing.com> wrote:
>
> Remove the unnecessary kick to the vCPU after writing to the vs_file
> of IMSIC in kvm_riscv_vcpu_aia_imsic_inject.
>
> For vCPUs that are running, writing to the vs_file directly forwards
> the interrupt as an MSI to them and does not need an extra kick.
>
> For vCPUs that are descheduled after emulating WFI, KVM will enable
> the guest external interrupt for that vCPU in
> kvm_riscv_aia_wakeon_hgei. This means that writing to the vs_file
> will cause a guest external interrupt, which will cause KVM to wake
> up the vCPU in hgei_interrupt to handle the interrupt properly.
>
> Signed-off-by: BillXiang <xiangwencheng@...xincomputing.com>

Queued this patch as a fix for Linux-6.14-rcX.

Thanks,
Anup

> ---
> v2: Revise the commit message to ensure it meets the required
>     standards for acceptance
>
>  arch/riscv/kvm/aia_imsic.c | 1 -
>  1 file changed, 1 deletion(-)
>
> diff --git a/arch/riscv/kvm/aia_imsic.c b/arch/riscv/kvm/aia_imsic.c
> index a8085cd8215e..29ef9c2133a9 100644
> --- a/arch/riscv/kvm/aia_imsic.c
> +++ b/arch/riscv/kvm/aia_imsic.c
> @@ -974,7 +974,6 @@ int kvm_riscv_vcpu_aia_imsic_inject(struct kvm_vcpu *vcpu,
>
>         if (imsic->vsfile_cpu >= 0) {
>                 writel(iid, imsic->vsfile_va + IMSIC_MMIO_SETIPNUM_LE);
> -               kvm_vcpu_kick(vcpu);
>         } else {
>                 eix = &imsic->swfile->eix[iid / BITS_PER_TYPE(u64)];
>                 set_bit(iid & (BITS_PER_TYPE(u64) - 1), eix->eip);
> --
> 2.46.2