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h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=vLKpHlXy9TeAxplzn8LuOxnhs+NZZT08I8jSb7+j1I6L64gZFqCGnchXfZ3Dqibh8 eQMv80pCWNlnv73z0GmxiYSywlJm2UuyVrhWN9MyheshF5MMnKprwZkReiNsEO3hTc KddnGGEGanHe0MFeVvE3aGvk5G7QNuyyTWu9q8xw= Date: Tue, 22 Sep 2026 17:25:58 +0100 From: Catalin Marinas To: "Aneesh Kumar K.V (Arm)" 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: <20260921144847.501151-3-aneesh.kumar@kernel.org> X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 077C714000F X-Stat-Signature: sy5e4no4wx9pwi8uua38bboezh44ycfj X-HE-Tag: 1790094364-976424 X-HE-Meta: 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 b3zXfVo8 FS+nBw1Z9gTk5WKuE3Fff6q8NLgs6TQALgLkELnW7b7adJSlcu6g1+navyU836P6fzKpLhLZtbsgO6WqIBKHzMVsn2Ehn8Evi3MRvb+1oea6N+WuA/5t31uxS3fW2w6t5O6MoetrBdPgvcfSn0XrfZAOnwnm2BV4dHFM8JJr6Hp2W83BjSshsnXhoqP7QFNjknOEzOI9YK4wfXOg6Z3ZEGAhzc9iFIDHyAHurQd7Ht99U34I= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Sep 21, 2026 at 08:18:36PM +0530, Aneesh Kumar K.V (Arm) wrote: > +int alloc_cc_shared_pages_node(int nid, gfp_t gfp, > + size_t requested, struct cc_shared_pages *mem) > +{ > + struct cc_shared_layout layout; > + struct page *page; > + unsigned int order; > + bool zero = gfp & __GFP_ZERO; > + int ret; > + > + if (!mem) > + return -EINVAL; > + > + ret = cc_shared_calc_layout(requested, &layout); > + if (ret) > + return ret; > + > + order = get_order(layout.shared_size); > + if (order > MAX_PAGE_ORDER) > + return -EINVAL; > + > + /* > + * State transitions require a linear-map address and may modify memory. > + * Allocate from low memory and defer requested zeroing until afterwards. > + */ > + gfp &= ~(__GFP_HIGHMEM | __GFP_ZERO); > + if (nid == NUMA_NO_NODE) > + page = alloc_pages(gfp, order); > + else > + page = alloc_pages_node(nid, gfp, order); > + if (!page) > + return -ENOMEM; > + > + ret = cc_make_shared(page_address(page), layout.shared_size); > + if (ret) { > + if (!cc_make_private(page_address(page), layout.shared_size)) > + __free_pages(page, order); > + else > + pr_warn_ratelimited("leaking %zu bytes with uncertain shared state\n", > + layout.shared_size); > + return ret; > + } > + > + if (zero) > + memset(page_address(page), 0, layout.shared_size); Does the memset() post sharing logic work for pKVM as well? If nothing clears it, we have a small window where guest data is leaked to the host. Is there a case where we *do not* need the memory cleared? If not, maybe we can move the logic in the arch set_memory_decrypted(). -- Catalin