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[159.2.239.150]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-532ae2c6a33sm1773871cf.0.2026.09.18.09.57.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 18 Sep 2026 09:57:55 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1x7buM-00000001zBN-2BHs; Fri, 18 Sep 2026 13:57:54 -0300 Date: Fri, 18 Sep 2026 13:57:54 -0300 From: Jason Gunthorpe To: Catalin Marinas Cc: "Aneesh Kumar K.V (Arm)" , linux-coco@lists.linux.dev, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, iommu@lists.linux.dev, Marc Zyngier , Marek Szyprowski , Robin Murphy , Steven Price , Suzuki K Poulose , Thomas Gleixner , Will Deacon Subject: Re: [PATCH v6 0/9] coco: guest: Enforce host page-size alignment for shared buffers Message-ID: <20260918165754.GG11599@ziepe.ca> References: <20260904103452.1197239-1-aneesh.kumar@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260918_095758_296872_0315606F X-CRM114-Status: GOOD ( 13.14 ) 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: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Sep 18, 2026 at 05:52:31PM +0100, Catalin Marinas wrote: > TBH, I'm tempted not to support this configuration at all, just fail > gracefully if the realm page size doesn't match the host's. However, if > that's a real world configuration, realm != host is going to be fairly common. host > realm is probably not that common, I would guess. > I wonder whether could we leverage the swiotlb mechanism but with a > separate io_tlb_mem as a shared coco allocator with the right > alignment and use this pool when force_dma_unencrypted() instead of > specific alloc_pages() with adjusted order. I propose we fix the far too low level set memory decrypted apis into proper allocators, with APIs that can handle a round up. Then see where we end up after that. If we can hide 90% of it in an allocator then lets see if we can open code the rest. Jason