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[121.45.204.168]) by smtp.gmail.com with ESMTPSA id i2-20020a17090332c200b0017834a6966csm367205plr.176.2022.09.20.14.46.24 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 20 Sep 2022 14:46:27 -0700 (PDT) Message-ID: <02490d2a-5e89-f342-f5b3-386406ffb2ea@ozlabs.ru> Date: Wed, 21 Sep 2022 07:46:21 +1000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:104.0) Gecko/20100101 Thunderbird/104.0 Subject: Re: [PATCH kernel v2] KVM: PPC: Make KVM_CAP_IRQFD_RESAMPLE support platform dependent To: Marc Zyngier References: <20220920125143.28009-1-aik@ozlabs.ru> <874jx2kp02.wl-maz@kernel.org> Content-Language: en-US From: Alexey Kardashevskiy In-Reply-To: <874jx2kp02.wl-maz@kernel.org> Cc: kvm@vger.kernel.org, kvm-ppc@vger.kernel.org, Nicholas Piggin , kvm-riscv@lists.infradead.org, Paolo Bonzini , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu On 21/09/2022 02:08, Marc Zyngier wr ote: > On Tue, 20 Sep 2022 13:51:43 +0100, > Alexey Kardashevskiy wrote: >> >> When introduced, IRQFD resampling worked on POWER8 with XICS. However >> KVM on POWER9 has never implemented it - the compatibility mode code >> ("XICS-on-XIVE") misses the kvm_notify_acked_irq() call and the native >> XIVE mode does not handle INTx in KVM at all. >> >> This moved the capability support advertising to platforms and stops >> advertising it on XIVE, i.e. POWER9 and later. >> >> Signed-off-by: Alexey Kardashevskiy >> Acked-by: Nicholas Piggin >> [For KVM RISC-V] >> Acked-by: Anup Patel >> --- >> Changes: >> v2: >> * removed ifdef for ARM64. > > The same argument applies to both x86 and s390, which do select > HAVE_KVM_IRQFD from the KVM config option. Only power allows this > option to be selected depending on the underlying interrupt controller > emulation. > > As for riscv and mips, they don't select HAVE_KVM_IRQFD, and this > isn't a user-selectable option. So why do they get patched at all? Before the patch, the capability was advertised on those, with your proposal it will stop. Which is a change in behavior which some may say requires a separate patch (like, one per platform). I am definitely overthinking it though and you are right. > My conclusion is that: > > - only power needs the #ifdefery in the arch-specific code > - arm64, s390 and x86 can use KVM_CAP_IRQFD_RESAMPLE without a #ifdef > - mips and riscv should be left alone Fair enough, thanks for the review! I'll post v3 shortly. > > Thanks, > > M. > -- Alexey _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm