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Mon, 7 Apr 2025 12:00:21 +0000 (UTC) Received: from localhost (dhcp-192-216.str.redhat.com [10.33.192.216]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id EF0F619541A6; Mon, 7 Apr 2025 12:00:19 +0000 (UTC) From: Cornelia Huck To: Oliver Upton , linux-arm-kernel@lists.infradead.org Cc: kvmarm@lists.linux.dev, Catalin Marinas , Will Deacon , Marc Zyngier , Oliver Upton Subject: Re: [PATCH] arm64: Expose AIDR_EL1 via sysfs In-Reply-To: <20250403231626.3181116-1-oliver.upton@linux.dev> Organization: "Red Hat GmbH, Sitz: Werner-von-Siemens-Ring 12, D-85630 Grasbrunn, Handelsregister: Amtsgericht =?utf-8?Q?M=C3=BCnchen=2C?= HRB 153243, =?utf-8?Q?Gesch=C3=A4ftsf=C3=BChrer=3A?= Ryan Barnhart, Charles Cachera, Michael O'Neill, Amy Ross" References: <20250403231626.3181116-1-oliver.upton@linux.dev> User-Agent: Notmuch/0.38.3 (https://notmuchmail.org) Date: Mon, 07 Apr 2025 14:00:17 +0200 Message-ID: <87jz7w9o6m.fsf@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: xbcBsVT45eMUlpcN_wfzjZ3WWpoHRYorv6V8CUmV528_1744027224 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250407_130205_268139_6341221E X-CRM114-Status: GOOD ( 13.94 ) 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 Thu, Apr 03 2025, Oliver Upton wrote: > The KVM PV ABI recently added a feature that allows the VM to discover > the set of physical CPU implementations, identified by a tuple of > {MIDR_EL1, REVIDR_EL1, AIDR_EL1}. Unlike other KVM PV features, the > expectation is that the VMM implements the hypercall instead of KVM as > it has the authoritative view of where the VM gets scheduled. > > To do this the VMM needs to know the values of these registers on any > CPU in the system. While MIDR_EL1 and REVIDR_EL1 are already exposed, > AIDR_EL1 is not. Provide it in sysfs along with the other identification > registers. > > Signed-off-by: Oliver Upton > --- > Documentation/ABI/testing/sysfs-devices-system-cpu | 1 + > Documentation/arch/arm64/cpu-feature-registers.rst | 13 +++++++------ > arch/arm64/include/asm/cpu.h | 1 + > arch/arm64/kernel/cpuinfo.c | 3 +++ > 4 files changed, 12 insertions(+), 6 deletions(-) Indeed, AIDR_EL1 should be available alongside the others. Reviewed-by: Cornelia Huck