From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id D1D3BC98302 for ; Tue, 22 Sep 2026 16:26:06 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 2B91810ED9C; Tue, 22 Sep 2026 16:26:06 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=arm.com header.i=@arm.com header.b="vLKpHlXy"; dkim-atps=neutral Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by gabe.freedesktop.org (Postfix) with ESMTP id 592DE10ED9C for ; Tue, 22 Sep 2026 16:26:04 +0000 (UTC) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 177FF1576; Tue, 22 Sep 2026 09:26:00 -0700 (PDT) Received: from arm.com (usa-sjc-mx-foss1.foss.arm.com [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 06CF23F632; Tue, 22 Sep 2026 09:26:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1790094363; bh=ayic+nVzRT7jF2h19D33qb2NxY0nfyFpS1c2IauCEkw=; 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-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" 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