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[34.22.131.218]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-442fd50b9b2sm42329115e9.12.2025.05.16.10.53.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 16 May 2025 10:53:31 -0700 (PDT) Date: Fri, 16 May 2025 18:53:27 +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 01/10] KVM: arm64: Handle huge mappings for np-guest CMOs Message-ID: References: <20250509131706.2336138-1-vdonnefort@google.com> <20250509131706.2336138-2-vdonnefort@google.com> <86bjrsg3az.wl-maz@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <86bjrsg3az.wl-maz@kernel.org> Hi, Thanks for having a look at the series. On Fri, May 16, 2025 at 01:15:00PM +0100, Marc Zyngier wrote: > On Fri, 09 May 2025 14:16:57 +0100, > Vincent Donnefort wrote: > > > > clean_dcache_guest_page() and invalidate_icache_guest_page() accept a > > size as an argument. But they also rely on fixmap, which can only map a > > single PAGE_SIZE page. > > > > With the upcoming stage-2 huge mappings for pKVM np-guests, those > > callbacks will get size > PAGE_SIZE. Loop the CMOs on a PAGE_SIZE basis > > until the whole range is done. > > > > Signed-off-by: Vincent Donnefort > > > > diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c > > index 31173c694695..23544928a637 100644 > > --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c > > +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c > > @@ -219,14 +219,28 @@ static void guest_s2_put_page(void *addr) > > > > static void clean_dcache_guest_page(void *va, size_t size) > > { > > - __clean_dcache_guest_page(hyp_fixmap_map(__hyp_pa(va)), size); > > - hyp_fixmap_unmap(); > > + WARN_ON(!PAGE_ALIGNED(size)); > > What if "va" isn't aligned? So the only callers are either for PAGE_SIZE or PMD_SIZE with the right alignment addr alignment. But happy to make this more future-proof, after all an ALIGN() is quite cheap. > > > + > > + while (size) { > > + __clean_dcache_guest_page(hyp_fixmap_map(__hyp_pa(va)), > > + PAGE_SIZE); > > + hyp_fixmap_unmap(); > > + va += PAGE_SIZE; > > + size -= PAGE_SIZE; > > + } > > I know pKVM dies on WARN, but this code "looks" unsafe. Can you align > va and size to be on page boundaries, so that we are 100% sure the > loop terminates? > > > } > > > > static void invalidate_icache_guest_page(void *va, size_t size) > > { > > - __invalidate_icache_guest_page(hyp_fixmap_map(__hyp_pa(va)), size); > > - hyp_fixmap_unmap(); > > + WARN_ON(!PAGE_ALIGNED(size)); > > + > > + while (size) { > > + __invalidate_icache_guest_page(hyp_fixmap_map(__hyp_pa(va)), > > + PAGE_SIZE); > > + hyp_fixmap_unmap(); > > + va += PAGE_SIZE; > > + size -= PAGE_SIZE; > > + } > > Same here. > > Thanks, > > M. > > -- > Without deviation from the norm, progress is not possible.