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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 89BECC5AC7A for ; Fri, 7 Aug 2026 11:58:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=Xd3UFDIz5wYvevp0q0lFRxsbOOvF3TFwe4o0b4um2rs=; b=E0UgrvpXjxlnS6ngC96KdRzN99 3VqYu1ys3GI6P77RvcH3uozVBfkFtMfjHY460ChH/A1vhT6n9sa18owrp2xw/c22v/4mbxK+dmlpA HAufaMS8PJvPH9oEPkYu1H0wSuZEmT5FkqNmSt89YC7tuFESUwRxiFx3gXf69w4CfmL/sPm81WUjj WHLJ3lP+GsoLOLbFdydfwbVwA1rd6y/MNDkCDEiT+ljDEnVvsRlGdLWEEPaRWD0UhJCHGRLQ8TXKt 3gJN7d+k/OjEFE5VNVzEin8/xu/ZlAJDb4u+89YnPePbXjmIjUA7zTzi91JyeEPC0nlhHCwTgh4Vj rvutnQuw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wsJDl-00000007z4d-1Z0m; Fri, 07 Aug 2026 11:58:41 +0000 Received: from sea.source.kernel.org ([2600:3c0a:e001:78e:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wsJDk-00000007z4T-0XBb for linux-arm-kernel@lists.infradead.org; Fri, 07 Aug 2026 11:58:40 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 9545243394; Fri, 7 Aug 2026 11:58:38 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id F2F7A1F00A3A; Fri, 7 Aug 2026 11:58:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786103918; bh=Xd3UFDIz5wYvevp0q0lFRxsbOOvF3TFwe4o0b4um2rs=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=Nb5CNrdE/4Z45mCov87EsHo7R+c/XppeMgdWkypZiJi0hG1F3qOgd2tMn8awJqvaS lbdSFBuX+8DZW+BUgsVb72bpNXzoeTOxLUMO7EfDoa8A1uqNuAgZxEIKcOk6xWqCjz inB/PGpqH/asRSsq2GTJ8yf/60nRgNhE7C1XyCY51qwFthllbwSfudh5hb9iKzACj7 QziTT7OLJ6iY0pmcLYRNlH75OV6VN8M2L9EGh7RPznyr9g/ejgHCUX6HO7rcff8qyK jVXAQEnK36ohiepgjg3IyQBDlNwN1AqiRdGYIzb5ul1D0/BFPUE3uuAab7MCjuibx8 FtaKWGZWWR0DA== Date: Fri, 7 Aug 2026 12:58:29 +0100 From: Will Deacon To: "Aneesh Kumar K.V (Arm)" Cc: iommu@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-coco@lists.linux.dev, Robin Murphy , Marek Szyprowski , Marc Zyngier , Steven Price , Suzuki K Poulose , Catalin Marinas , Jiri Pirko , Jason Gunthorpe , Mostafa Saleh , Petr Tesarik , Alexey Kardashevskiy , Dan Williams , Xu Yilun , linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Sven Schnelle , x86@kernel.org Subject: Re: [PATCH] arm64: swiotlb: Keep the default size for protected guests Message-ID: References: <20260717180442.110954-18-aneesh.kumar@kernel.org> <20260807092612.2202005-1-aneesh.kumar@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260807092612.2202005-1-aneesh.kumar@kernel.org> 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, Aug 07, 2026 at 02:56:12PM +0530, Aneesh Kumar K.V (Arm) wrote: > Realm guests and protected KVM guests may require swiotlb for device DMA > even when all system RAM is addressable by the DMA zones. > > Do not reduce the SWIOTLB buffer to the kmalloc-bouncing size for these > guests, as the reduced number of slots can be exhausted during CCA guest > operation. > > Fixes: 30c5e45ee2c5 ("dma-direct: make dma_direct_map_phys() honor DMA_ATTR_CC_SHARED") > Signed-off-by: Aneesh Kumar K.V (Arm) > --- > arch/arm64/mm/init.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c > index e308a7cabd12..24caaf10e755 100644 > --- a/arch/arm64/mm/init.c > +++ b/arch/arm64/mm/init.c > @@ -339,7 +339,8 @@ void __init arch_mm_preinit(void) > { > unsigned int flags = SWIOTLB_VERBOSE; > > - if (max_pfn <= PFN_DOWN(arm64_dma_phys_limit)) { > + if (!cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT) && > + max_pfn <= PFN_DOWN(arm64_dma_phys_limit)) { Protected guests under pKVM rely on restricted DMA, so won't this just waste memory for them? Will