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Mon, 03 Jun 2024 15:31:34 +0100 Date: Mon, 03 Jun 2024 15:31:33 +0100 Message-ID: <86ikyqkshm.wl-maz@kernel.org> From: Marc Zyngier To: Mark Brown Cc: Fuad Tabba , kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, will@kernel.org, qperret@google.com, seanjc@google.com, alexandru.elisei@arm.com, catalin.marinas@arm.com, philmd@linaro.org, james.morse@arm.com, suzuki.poulose@arm.com, oliver.upton@linux.dev, mark.rutland@arm.com, joey.gouly@arm.com, rananta@google.com, yuzenghui@huawei.com Subject: Re: [PATCH v3 05/11] KVM: arm64: Eagerly restore host fpsimd/sve state in pKVM In-Reply-To: <382e0746-84a4-4c59-9187-ca9b87f9d265@sirena.org.uk> References: <20240528125914.277057-1-tabba@google.com> <20240528125914.277057-6-tabba@google.com> <6e473418-dbce-4008-94fe-f60174d3f8fe@sirena.org.uk> <86jzj6kuh4.wl-maz@kernel.org> <382e0746-84a4-4c59-9187-ca9b87f9d265@sirena.org.uk> 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/29.2 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: broonie@kernel.org, tabba@google.com, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, will@kernel.org, qperret@google.com, seanjc@google.com, alexandru.elisei@arm.com, catalin.marinas@arm.com, philmd@linaro.org, james.morse@arm.com, suzuki.poulose@arm.com, oliver.upton@linux.dev, mark.rutland@arm.com, joey.gouly@arm.com, rananta@google.com, 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-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240603_073138_156397_1E088DA5 X-CRM114-Status: GOOD ( 20.82 ) 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, 03 Jun 2024 15:15:37 +0100, Mark Brown wrote: > > On Mon, Jun 03, 2024 at 02:48:39PM +0100, Marc Zyngier wrote: > > Mark Brown wrote: > > > On Mon, Jun 03, 2024 at 09:37:16AM +0100, Fuad Tabba wrote: > > > > > Also, one of the concerns in terms of performance is now with > > > > nested-virt support being added, and the overhead of doing the > > > > conditional update when we know that it's unlikely that anyone is > > > > implementing vectors as big as the max. > > > > I guess there's the option of doing a restore of a value fixed during > > > initialisation instead? > > > And what do we gain from that? > > Reducing the number of places that need updating. That'd be assuming that the host side value never requires any change and will be OK with a fixed value. Given that this highly hypothetical change would be likely to be a hierarchical control much like ZCR_ELx is today, the fixed value is likely to change on a regular basis. In any case, this is something we can (re)evaluate when we get to it. If ever. M. -- Without deviation from the norm, progress is not possible. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel