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Wed, 11 Nov 2026 21:28:46 -0800 (PST) Received: from localhost ([2c0f:3d00:6be:8900:ce5e:9212:ea4b:f30]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-49944d646f9sm11119109f8f.32.2026.11.11.21.28.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 11 Nov 2026 21:28:46 -0800 (PST) Date: Thu, 12 Nov 2026 08:28:42 +0300 From: Dan Carpenter To: Marc Zyngier Cc: Dan Carpenter , Oliver Upton , Fuad Tabba , Joey Gouly , Steffen Eiden , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , Mark Rutland , linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, Karthik Bhargavan , =?iso-8859-1?Q?Cl=E9ment?= Blaudeau Subject: Re: [PATCH] KVM: arm64: nv: Initialize hw_mmu to NULL for nested vCPUs Message-ID: References: <86ld6z1782.wl-maz@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <86ld6z1782.wl-maz@kernel.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20261111_212852_793437_4F68365C X-CRM114-Status: GOOD ( 15.72 ) X-Spam-Score: -0.2 (/) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" X-Spam-Status: No, score=-3.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_EF,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Wed, Nov 11, 2026 at 07:46:53PM +0000, Marc Zyngier wrote: > > I think this really needs a comment to explain why we repaint hw_mmu > to NULL, because the next idiot who looks at this (likely me) will > probably remove this line... > > The other thing is that this means that nothing can evaluate > vcpu->arch.hw_mmu anywhere outside of the loaded path, as it can be > NULL. I *think* this is OK, but I need to really convince myself... > > I'd like to add something like: > > /* > * We can't rely on the S2 MMU being the canonical one, > * as userspace can restore a nested context. Nuke the > * hw_mmu early to ensure that we pick the correct one > * load time. It also means that we can't rely on hw_mmu > * being set to anything useful if the vcpu isn't loaded. > */ > > If that works for you, I'll squash that in. Absolutely. Thanks so much. regards, dan carpenter