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Thu, 20 Nov 2025 14:51:45 +0000 Date: Thu, 20 Nov 2025 14:51:44 +0000 Message-ID: <865xb4sqnz.wl-maz@kernel.org> From: Marc Zyngier To: Joey Gouly Cc: kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Suzuki K Poulose , Oliver Upton , Zenghui Yu Subject: Re: [PATCH 2/5] KVM: arm64: Force trap of GMID_EL1 when the guest doesn't have MTE In-Reply-To: <20251120143419.GA2325986@e124191.cambridge.arm.com> References: <20251120133202.2037803-1-maz@kernel.org> <20251120133202.2037803-3-maz@kernel.org> <20251120143419.GA2325986@e124191.cambridge.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) 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: joey.gouly@arm.com, kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, suzuki.poulose@arm.com, oupton@kernel.org, yuzenghui@huawei.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 Thu, 20 Nov 2025 14:34:19 +0000, Joey Gouly wrote: > > On Thu, Nov 20, 2025 at 01:31:59PM +0000, Marc Zyngier wrote: > > If our host has MTE, but the guest doesn't, make sure we set HCR_EL2.TID5 > > to force GMID_EL1 being trapped. > > > > Signed-off-by: Marc Zyngier > > --- > > arch/arm64/kvm/sys_regs.c | 2 ++ > > 1 file changed, 2 insertions(+) > > > > diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c > > index 84e6f04220589..40f32b017f107 100644 > > --- a/arch/arm64/kvm/sys_regs.c > > +++ b/arch/arm64/kvm/sys_regs.c > > @@ -5558,6 +5558,8 @@ static void vcpu_set_hcr(struct kvm_vcpu *vcpu) > > > > if (kvm_has_mte(vcpu->kvm)) > > vcpu->arch.hcr_el2 |= HCR_ATA; > > + else if (id_aa64pfr1_mte(read_sanitised_ftr_reg(SYS_ID_AA64PFR1_EL1))) > > + vcpu->arch.hcr_el2 |= HCR_TID5; > > This is because we want to enable the trapping regardless of CONFIG_ARM64_MTE > (so we can't use system_supports_mte()). Indeed. In general, we cannot rely on the kernel's own configuration, since the guest sees most of the actual HW. > > Reviewed-by: Joey Gouly Thanks! M. -- Without deviation from the norm, progress is not possible.