From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marc Zyngier Date: Tue, 20 Sep 2022 16:08:13 +0000 Subject: Re: [PATCH kernel v2] KVM: PPC: Make KVM_CAP_IRQFD_RESAMPLE support platform dependent Message-Id: <874jx2kp02.wl-maz@kernel.org> List-Id: References: <20220920125143.28009-1-aik@ozlabs.ru> In-Reply-To: <20220920125143.28009-1-aik@ozlabs.ru> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Alexey Kardashevskiy Cc: kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm-riscv@lists.infradead.org, Paolo Bonzini , Anup Patel , kvm-ppc@vger.kernel.org, Nicholas Piggin 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? 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 Thanks, M. -- Without deviation from the norm, progress is not possible.