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Sun, 27 Sep 2026 09:26:46 +0000 Date: Sun, 27 Sep 2026 10:29:54 +0100 Message-ID: <87v77r2ga5.wl-maz@kernel.org> From: Marc Zyngier To: Suzuki K Poulose Cc: Catalin Marinas , kvm@vger.kernel.org, kvmarm@lists.linux.dev, will@kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, steven.price@arm.com, aneesh.kumar@kernel.org, oupton@kernel.org, gshan@redhat.com, joey.gouly@arm.com, tabba@google.com, yuzenghui@huawei.com, linux-coco@lists.linux.dev, gankulkarni@os.amperecomputing.com, sdonthineni@nvidia.com, alpergun@google.com, fj0570is@fujitsu.com, WeiLin.Chang@arm.com, lpieralisi@kernel.org, enju.kohei@fujitsu.com, sudeep.holla@arm.com, jonathan.cameron@oss.qualcomm.com Subject: Re: [PATCH v19 2/7] firmware: arm_rmm: Check for RMI support at init In-Reply-To: References: <20260924135201.850038-1-suzuki.poulose@arm.com> <20260924135201.850038-3-suzuki.poulose@arm.com> 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) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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: suzuki.poulose@arm.com, catalin.marinas@arm.com, kvm@vger.kernel.org, kvmarm@lists.linux.dev, will@kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, steven.price@arm.com, aneesh.kumar@kernel.org, oupton@kernel.org, gshan@redhat.com, joey.gouly@arm.com, tabba@google.com, yuzenghui@huawei.com, linux-coco@lists.linux.dev, gankulkarni@os.amperecomputing.com, sdonthineni@nvidia.com, alpergun@google.com, fj0570is@fujitsu.com, WeiLin.Chang@arm.com, lpieralisi@kernel.org, enju.kohei@fujitsu.com, sudeep.holla@arm.com, jonathan.cameron@oss.qualcomm.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false On Fri, 25 Sep 2026 16:23:49 +0100, Suzuki K Poulose wrote: > > On 25/09/2026 11:42, Catalin Marinas wrote: > > On Thu, Sep 24, 2026 at 02:51:56PM +0100, Suzuki K Poulose wrote: > >> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > >> index 32102c3912fa7..e8b29983b0021 100644 > >> --- a/arch/arm64/kernel/cpufeature.c > >> +++ b/arch/arm64/kernel/cpufeature.c > >> @@ -293,6 +293,7 @@ static const struct arm64_ftr_bits ftr_id_aa64isar3[] = { > >> static const struct arm64_ftr_bits ftr_id_aa64pfr0[] = { > >> ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64PFR0_EL1_CSV3_SHIFT, 4, 0), > >> ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64PFR0_EL1_CSV2_SHIFT, 4, 0), > >> + ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64PFR0_EL1_RME_SHIFT, 4, 0), > > > > I think we end up exposing this to (any) guest unless we mask it out in > > sanitise_id_aa64dfr0_el1(). Do the guests care about the RME version? I > > Valid point. I personally don't think this matters. The FEAT_RME alone > is not useful or harmful. I could mask it in KVM as a safe bet. Is there *any* case where the guest (realm or not) should know it is running on RME enabled HW? I can perfectly imagine that someone would implement something looking like CCA on non-RME systems. M. -- Jazz isn't dead. It just smells funny.