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From: Oliver Upton To: Sean Christopherson Cc: Mark Brown , Marc Zyngier , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Paolo Bonzini , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, kvm@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, Andrew Jones , James Houghton , David Woodhouse , linux-next@vger.kernel.org Subject: Re: [PATCH v3 03/14] KVM: selftests: Return a value from vcpu_get_reg() instead of using an out-param Message-ID: References: <20241009154953.1073471-1-seanjc@google.com> <20241009154953.1073471-4-seanjc@google.com> <39ea24d8-9dae-447a-ae37-e65878c3806f@sirena.org.uk> 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: X-Migadu-Flow: FLOW_OUT Hey, On Fri, Nov 01, 2024 at 07:48:00AM -0700, Sean Christopherson wrote: > On Fri, Nov 01, 2024, Mark Brown wrote: > > On Wed, Oct 09, 2024 at 08:49:42AM -0700, Sean Christopherson wrote: > > > Return a uint64_t from vcpu_get_reg() instead of having the caller provide > > > a pointer to storage, as none of the vcpu_get_reg() usage in KVM selftests > > > accesses a register larger than 64 bits, and vcpu_set_reg() only accepts a > > > 64-bit value. If a use case comes along that needs to get a register that > > > is larger than 64 bits, then a utility can be added to assert success and > > > take a void pointer, but until then, forcing an out param yields ugly code > > > and prevents feeding the output of vcpu_get_reg() into vcpu_set_reg(). > > > > This commit, which is in today's -next as 5c6c7b71a45c9c, breaks the > > build on arm64: > > > > aarch64/psci_test.c: In function ‘host_test_system_off2’: > > aarch64/psci_test.c:247:9: error: too many arguments to function ‘vcpu_get_reg’ > > 247 | vcpu_get_reg(target, KVM_REG_ARM_PSCI_VERSION, &psci_version); > > | ^~~~~~~~~~~~ > > In file included from aarch64/psci_test.c:18: > > include/kvm_util.h:705:24: note: declared here > > 705 | static inline uint64_t vcpu_get_reg(struct kvm_vcpu *vcpu, uint64_t id) > > | ^~~~~~~~~~~~ > > At top level: > > cc1: note: unrecognized command-line option ‘-Wno-gnu-variable-sized-type-not-at > > -end’ may have been intended to silence earlier diagnostics > > > > since the updates done to that file did not take account of 72be5aa6be4 > > ("KVM: selftests: Add test for PSCI SYSTEM_OFF2") which has been merged > > in the kvm-arm64 tree. > > Bugger. In hindsight, it's obvious that of course arch selftests would add usage > of vcpu_get_reg(). > > Unless someone has a better idea, I'll drop the series from kvm-x86, post a new > version that applies on linux-next, and then re-apply the series just before the > v6.13 merge window (rinse and repeat as needed if more vcpu_get_reg() users come > along). Can you instead just push out a topic branch and let the affected maintainers deal with it? This is the usual way we handle conflicts between trees... > That would be a good oppurtunity to do the $(ARCH) directory switch[*] too, e.g. > have a "selftests_late" or whatever topic branch. The right time to do KVM-wide changes (even selftests) is *early* in the development cycle, not last minute. It gives us plenty of time to iron out the wrinkles. > Sorry for the pain Mark, you've been playing janitor for us too much lately. +1, appreciate your help on this. -- Thanks, Oliver