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Wed, 23 Sep 2026 10:23:34 -0700 (PDT) Received: from ziepe.ca ([130.41.10.202]) by smtp.gmail.com with ESMTPSA id 5614622812f47-4d5c522604asm2686648b6e.15.2026.09.23.10.23.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 23 Sep 2026 10:23:34 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1x9Qgv-0000000E9nH-0xvE; Wed, 23 Sep 2026 14:23:33 -0300 Date: Wed, 23 Sep 2026 14:23:33 -0300 From: Jason Gunthorpe To: Kameron Carr Cc: "Aneesh Kumar K.V" , mhklinux@outlook.com, Catalin Marinas , linux-coco@lists.linux.dev, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, iommu@lists.linux.dev, Andrew Morton , christian.koenig@amd.com, Joerg Roedel , Marc Zyngier , Marek Szyprowski , Robin Murphy , Steven Price , Sumit Semwal , Suzuki K Poulose , Thomas Gleixner , Will Deacon , dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, linux-media@vger.kernel.org, linux-mm@kvack.org Subject: Re: [RFC PATCH v7 02/13] mm: Add an allocator for CoCo shared memory Message-ID: <20260923172333.GM1540250@ziepe.ca> References: <20260921144847.501151-3-aneesh.kumar@kernel.org> <20260923130611.GF1540250@ziepe.ca> <20260923152124.GG1540250@ziepe.ca> <5cbe0bde-47d8-41ca-b244-bc0329d0d066@linux.microsoft.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5cbe0bde-47d8-41ca-b244-bc0329d0d066@linux.microsoft.com> X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 0163440005 X-Stat-Signature: nnu7sjj1yxn6kirr9ef54ej9zhpbpd5h X-HE-Tag: 1790184215-73471 X-HE-Meta: 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 mChup8rh a65X5NuioaeEZY/NxBo8UHGhBmK0JNt5+i9tsHsveWQ7py8N6+khfAvs9C7lvLukq1a4eq2q0MGIIbnJ66uSE7GTFgO7YS/+mKFqeP3wurabJJnUD9Rp+DQLNq70lQbzLKMThg9BQb3CWna22iTz1GE1l24/GFa4/fovSQIA665bwtL3PxyaOTvitEVuoh6xoY7YKmqQmuAYMb6WeZbAs52b9UWE+rRxXhziKhty0G/FZ5335dpbqsuGJWmFPqpGPW0sA0+Ed9MAbcV1Wnq8jRdEdNgqnTbCwZHp/ Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Sep 23, 2026 at 09:28:54AM -0700, Kameron Carr wrote: > On 9/23/2026 8:21 AM, Jason Gunthorpe wrote: > > On Wed, Sep 23, 2026 at 08:28:57PM +0530, Aneesh Kumar K.V wrote: > > > >> I'm also considering requiring the address passed to cc_make_shared() to > >> be in the linear map. This is currently required by both TDX and CCA, > >> while AMD SNP appears to support vmalloc addresses. The only user of > >> that vmalloc support is Hyper-V VMBus GPADL setup > >> (vmbus_establish_gpadl()). How should the generic CoCo shared-memory > >> allocator handle this? > > > > vmbus_establish_gpadl() is the the same wrong abstraction as the arch > > code. Get rid of it and use vmbus_establish_gpadl_caller_decrypted(): > > > > pdata->recv_buf = vzalloc(RECV_BUFFER_SIZE); > > if (!pdata->recv_buf) { > > ret = -ENOMEM; > > goto fail_free_ring; > > } > > > > ret = vmbus_establish_gpadl(channel, pdata->recv_buf, > > RECV_BUFFER_SIZE, &pdata->recv_gpadl); > > > > > > So you made an allocator that returns folios, now you just need to > > use that allocator to implement a kvzalloc wrapper. ARM can call vmap > > on decrypted memory with pgprot_decrypted(), right? > > > > Or maybe this can use vmbus_alloc_buffer(), it already does it. > > Michael Kelley recently proposed [1] moving all ring buffer allocations > to use vmbus_alloc_buffer(). If we move forward with this, it should > remove the dependency on vmalloc support. Even better vmbus_alloc_buffer() can use the new allocator API directly so it doesn't need to open code the set_memory_decrypted arch call. Lets do it! Jaon