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Wed, 19 Feb 2025 00:36:06 -0800 (PST) Date: Wed, 19 Feb 2025 09:36:05 +0100 From: Andrew Jones To: BillXiang Cc: anup@brainfault.org, kvm-riscv@lists.infradead.org, kvm@vger.kernel.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, atishp@atishpatra.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu Subject: Re: [PATCH] riscv: KVM: Remove unnecessary vcpu kick Message-ID: <20250219-badec60b9b12834cf534dcbf@orel> References: <20250219015426.1939-1-xiangwencheng@lanxincomputing.com> 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=us-ascii Content-Disposition: inline In-Reply-To: <20250219015426.1939-1-xiangwencheng@lanxincomputing.com> On Wed, Feb 19, 2025 at 09:54:26AM +0800, BillXiang wrote: > Thank you Andrew Jones, forgive my errors in the last email. >From here down is all exactly the same as your first email, which I already completely replied to. > 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. > > 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); > } else { > eix = &imsic->swfile->eix[iid / BITS_PER_TYPE(u64)]; > set_bit(iid & (BITS_PER_TYPE(u64) - 1), eix->eip); > -- > 2.46.2