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h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=N3sYQlebo9JuaPrX/aY4BYXg4kl12bBh2l+dg5S1TpD/sd1OrXwH32xGOiPW5K434 UuBzqurGcjPFaH0amX7WpALPGj4+fE2hTuRxrmfBQJcpZcj2x3NVvhpckvNi+KxnQI AtUULuSivZdyBUiepK0KoTPupOCiWcVRdZmElWyM= Date: Wed, 23 Sep 2026 11:10:32 +0100 From: Catalin Marinas To: "Aneesh Kumar K.V" Cc: 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, Jason Gunthorpe , 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: References: <20260921144847.501151-1-aneesh.kumar@kernel.org> <20260921144847.501151-3-aneesh.kumar@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: t6c6je3sapqs3kqu77pymnfbpmactb5m X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 08CB4140004 X-HE-Tag: 1790158238-648811 X-HE-Meta: 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 JuiGvfNP A9Hv9b6bdSNhdpzjtcNI3VXttmrPelIbmj6zRM0AtOwwqURJDm0TXUz9wqnIyFZXTWgvoA2H6RldZJwLkOWZ7UOIpMlcPfcRknc8AngsOYXmn2jIOtxQzf91QCQJ/FoROvaPHwBr7koh+WSjbXbvQLHkI5yvIR/E2s8Beh5czP0nCWciopueTeX8VC8rTYO0G/HzvTivTY+qtDQr9lyDoGhfaEVOyMllL+T7BYpNw6P1SJ6mGGv9dqlPtCrIHfW09wGuH2TxZYyuDxkI8fnnWu54ixo1kOMGeSfZY34iUjiXPs60rvYLpV/jmyeFTzugzD9uYHLdY1Cal5qB3ssRUEYGa8g== 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 02:01:08PM +0530, Aneesh Kumar K.V wrote: > I was pointed to this email thread: > > https://lore.kernel.org/all/c25502d3-35c6-4281-a9ec-856f789fb1b4@arm.com > > This makes a stronger case for having a CoCo shared memory allocator > that captures all these restrictions. It also means that > alloc_cc_shared_pages_node() needs: > > if (WARN_ON_ONCE(!gfpflags_allow_blocking(gfp))) > return -EINVAL; > > might_sleep(); I think gfpflags_allow_blocking() is the wrong predicate. It checks for __GFP_DIRECT_RECLAIM but we have callers like dma-buf which clear the flag (see HIGH_ORDER_GFP). ITS allocations also use GFP_NOWAIT, so they'll fail here. I'd just keep a might_sleep() in cc_make_*() and ignore gfp flags checking. Passing a no-blocking GFP flag doesn't necessarily mean the caller cannot sleep. It might also happen early enough (like its_init()) not to care - __might_resched() skips the warning if SYSTEM_BOOTING. -- Catalin