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Mon, 10 Nov 2025 13:11:05 +0000 Date: Mon, 10 Nov 2025 13:11:05 +0000 Message-ID: <865xbiuj6e.wl-maz@kernel.org> From: Marc Zyngier To: Mark Brown Cc: kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org, Joey Gouly , Suzuki K Poulose , Oliver Upton , Zenghui Yu , Peter Maydell , Paolo Bonzini , Aishwarya.TCV@arm.com Subject: Re: [PATCH v2 3/3] KVM: arm64: Limit clearing of ID_{AA64PFR0,PFR1}_EL1.GIC to userspace irqchip In-Reply-To: References: <20251030122707.2033690-1-maz@kernel.org> <20251030122707.2033690-4-maz@kernel.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/30.1 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: broonie@kernel.org, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org, joey.gouly@arm.com, suzuki.poulose@arm.com, oliver.upton@linux.dev, yuzenghui@huawei.com, peter.maydell@linaro.org, pbonzini@redhat.com, Aishwarya.TCV@arm.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, 10 Nov 2025 12:51:55 +0000, Mark Brown wrote: > > On Thu, Oct 30, 2025 at 12:27:07PM +0000, Marc Zyngier wrote: > > Now that the idreg's GIC field is in sync with the irqchip, limit > > the runtime clearing of these fields to the pathological case where > > we do not have an in-kernel GIC. > > > > While we're at it, use the existing API instead of open-coded > > accessors to access the ID regs. > > Today's next/pending-fixes is showing regressions on a range of physical > arm64 platforms (including at least a bunch of A53 systems, an A55 one > and an A72 one) in the steal_time selftest which bisect to this patch. > We get asserts in the kernel on ID register sets: > > [ 150.872407] WARNING: CPU: 0 PID: 2865 at arch/arm64/kvm/sys_regs.c:2353 kvm_set_vm_id_reg+0x9c/0xf4 > > ... > > [ 151.045312] Call trace: > [ 151.047780] kvm_set_vm_id_reg+0x9c/0xf4 (P) > [ 151.052098] kvm_finalize_sys_regs+0x88/0x240 > [ 151.056504] kvm_arch_vcpu_run_pid_change+0xb4/0x438 > [ 151.061527] kvm_vcpu_ioctl+0x92c/0x9d0 Please name the platforms this fails on. Here, on a sample of one A72 box, I don't see the issue: maz@sy-borg:~$ ./steal_time Random seed: 0x6b8b4567 TAP version 13 1..4 ok 1 vcpu0 ok 2 vcpu1 ok 3 vcpu2 ok 4 vcpu3 # Totals: pass:4 fail:0 xfail:0 xpass:0 skip:0 error:0 Thanks, M. -- Without deviation from the norm, progress is not possible.