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[34.22.131.218]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-442f3380539sm118985205e9.16.2025.05.16.11.03.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 16 May 2025 11:03:18 -0700 (PDT) Date: Fri, 16 May 2025 19:03:14 +0100 From: Vincent Donnefort To: Marc Zyngier Cc: oliver.upton@linux.dev, joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, will@kernel.org, qperret@google.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH v4 10/10] KVM: arm64: np-guest CMOs with PMD_SIZE fixmap Message-ID: References: <20250509131706.2336138-1-vdonnefort@google.com> <20250509131706.2336138-11-vdonnefort@google.com> <864ixkfynk.wl-maz@kernel.org> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <864ixkfynk.wl-maz@kernel.org> > > +} > > + > > static void clean_dcache_guest_page(void *va, size_t size) > > { > > WARN_ON(!PAGE_ALIGNED(size)); > > > > while (size) { > > - __clean_dcache_guest_page(hyp_fixmap_map(__hyp_pa(va)), > > - PAGE_SIZE); > > - hyp_fixmap_unmap(); > > - va += PAGE_SIZE; > > - size -= PAGE_SIZE; > > + size_t fixmap_size = size == PMD_SIZE ? size : PAGE_SIZE; > > + void *addr = __fixmap_guest_page(va, &fixmap_size); > > + > > + __clean_dcache_guest_page(addr, fixmap_size); > > + __fixunmap_guest_page(fixmap_size); > > + > > + size -= fixmap_size; > > + va += fixmap_size; > > Can this ever be called with a *multiple* of PMD_SIZE? In this case > you'd still end-up doing PAGE_SIZEd-bite CMOs until there is only > PMD_SIZE left, ruining the optimisation. > > I think this needs fixing. So this can be only called with size either equal to PAGE_SIZE or PMD_SIZE. I wasn't sure if it was worth to make it more generic than it needs. But like for the first patch, I can make it more future-proof by handling size > PMD_SIZE. > > > } > > } > > [...]