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Mon, 02 Mar 2026 17:58:14 +0000 Date: Mon, 02 Mar 2026 17:58:12 +0000 Message-ID: <86ldga866j.wl-maz@kernel.org> From: Marc Zyngier To: Ben Horgan Cc: amitsinght@marvell.com, baisheng.gao@unisoc.com, baolin.wang@linux.alibaba.com, carl@os.amperecomputing.com, dave.martin@arm.com, david@kernel.org, dfustini@baylibre.com, fenghuay@nvidia.com, gshan@redhat.com, james.morse@arm.com, jonathan.cameron@huawei.com, kobak@nvidia.com, lcherian@marvell.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, peternewman@google.com, punit.agrawal@oss.qualcomm.com, quic_jiles@quicinc.com, reinette.chatre@intel.com, rohit.mathew@arm.com, scott@os.amperecomputing.com, sdonthineni@nvidia.com, tan.shaopeng@fujitsu.com, xhao@linux.alibaba.com, catalin.marinas@arm.com, will@kernel.org, corbet@lwn.net, oupton@kernel.org, joey.gouly@arm.com, suzuki.poulose@arm.com, kvmarm@lists.linux.dev, zengheng4@huawei.com, linux-doc@vger.kernel.org, Shaopeng Tan Subject: Re: [PATCH v5 11/41] KVM: arm64: Force guest EL1 to use user-space's partid configuration In-Reply-To: <20260224175720.2663924-12-ben.horgan@arm.com> References: <20260224175720.2663924-1-ben.horgan@arm.com> <20260224175720.2663924-12-ben.horgan@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; 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SAEximRunCond expanded to false On Tue, 24 Feb 2026 17:56:50 +0000, Ben Horgan wrote: > > From: James Morse > > While we trap the guest's attempts to read/write the MPAM control > registers, the hardware continues to use them. Guest-EL0 uses KVM's > user-space's configuration, as the value is left in the register, and > guest-EL1 uses either the host kernel's configuration, or in the case of > VHE, the UNKNOWN reset value of MPAM1_EL1. > > We want to force the guest-EL1 to use KVM's user-space's MPAM > configuration. On nVHE rely on MPAM0_EL1 and MPAM1_EL1 always being > programmed the same and on VHE copy MPAM0_EL1 into the guest's > MPAM1_EL1. There is no need to restore as this is out of context once TGE > is set. > > Tested-by: Gavin Shan > Tested-by: Shaopeng Tan > Tested-by: Peter Newman > Tested-by: Zeng Heng > Reviewed-by: Shaopeng Tan > Reviewed-by: Jonathan Cameron > Signed-off-by: James Morse > Signed-off-by: Ben Horgan Acked-by: Marc Zyngier M. -- Without deviation from the norm, progress is not possible.