[PATCH v2] riscv: KVM: Remove unnecessary vcpu kick

[PATCH v2] riscv: KVM: Remove unnecessary vcpu kick

[BillXiang]

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@lanxincomputing.com>
---
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

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

[Andrew Jones]

On Fri, Feb 21, 2025 at 06:45:38PM +0800, BillXiang 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@lanxincomputing.com>
> ---
> 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

Reviewed-by: Andrew Jones <ajones@ventanamicro.com>

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

[Radim Krčmář]

2025-02-21T18:45:38+08:00, BillXiang <xiangwencheng@lanxincomputing.com>:
> 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@lanxincomputing.com>
> ---
> v2: Revise the commit message to ensure it meets the required 
>     standards for acceptance

Nice, thanks.

Reviewed-by: Radim Krčmář <rkrcmar@ventanamicro.com>

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

[Anup Patel]

On Fri, Feb 21, 2025 at 4:16 PM BillXiang
<xiangwencheng@lanxincomputing.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@lanxincomputing.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

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

[patchwork-bot+linux-riscv]

Hello:

This patch was applied to riscv/linux.git (for-next)
by Anup Patel <anup@brainfault.org>:

On Fri, 21 Feb 2025 18:45:38 +0800 you 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.
> 
> [...]

Here is the summary with links:
  - [v2] riscv: KVM: Remove unnecessary vcpu kick
    https://git.kernel.org/riscv/c/d252435aca44

You are awesome, thank you!
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