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Tue, 18 Feb 2025 09:48:41 -0800 (PST) Date: Tue, 18 Feb 2025 18:48:41 +0100 From: Andrew Jones To: =?utf-8?B?6aG55paH5oiQ?= Cc: "kvm-riscv@lists.infradead.org" , "anup@brainfault.org" , "atishp@atishpatra.org" , "paul.walmsley@sifive.com" , "palmer@dabbelt.com" , "aou@eecs.berkeley.edu" , "kvm@vger.kernel.org" , "linux-riscv@lists.infradead.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] riscv: KVM: Remove unnecessary vcpu kick Message-ID: <20250218-57a3a16e477f83a8c267d120@orel> References: <38cc241c40a8ef2775e304d366bcd07df733ecf0.1d66512d.85e4.41a5.8cf7.4c1fdb05d775@feishu.cn> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <38cc241c40a8ef2775e304d366bcd07df733ecf0.1d66512d.85e4.41a5.8cf7.4c1fdb05d775@feishu.cn> On Tue, Feb 18, 2025 at 04:00:24PM +0800, 项文成 wrote: > From 30dd00f6886119ecc5c39b6b88f8617a57e598fc Mon Sep 17 00:00:00 2001 > From: BillXiang > Date: Tue, 18 Feb 2025 15:45:52 +0800 > Subject: [PATCH] riscv: KVM: Remove unnecessary vcpu kick > > Hello everyone, > I'm wondering whether it's necessary to kick the virtual hart > after writing to the vsfile of IMSIC. > From my understanding, writing to the vsfile should directly > forward the interrupt as MSI to the virtual hart. This means that > an additional kick should not be necessary, as it would cause the > vCPU to exit unnecessarily and potentially degrade performance. > I've tested this behavior in QEMU, and it seems to work perfectly > fine without the extra kick. > Would appreciate any insights or confirmation on this! > Best regards. The above should be in a cover letter so the commit message can be written following the guidelines of [1] [1] Documentation/process/submitting-patches.rst > > Signed-off-by: BillXiang > --- >  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); We can't completely remove the kick, but we could replace it with a kvm_vcpu_wake_up(). There's also a kick in kvm_riscv_vcpu_vstimer_expired() which could be a kvm_vcpu_wake_up() when hideleg has IRQ_VS_TIMER set (which it currently always does). Thanks, drew >         } else { >                 eix = &imsic->swfile->eix[iid / BITS_PER_TYPE(u64)]; >                 set_bit(iid & (BITS_PER_TYPE(u64) - 1), eix->eip); > -- > 2.46.2 > > -- > kvm-riscv mailing list > kvm-riscv@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/kvm-riscv