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 B0942CD5BD7 for ; Thu, 5 Sep 2024 16:31:02 +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:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=S0MHIzgzN4aU9BAfLMWWtTugRem1l63ddBbwwUAF0eY=; b=mVXILRdzM1NPTsVwvbULA/btbV 1dvB/IMw0m9VgB38EdTNjPp5oagrF37eZlvQv9V48Ek0WjFp9ZcCl27foWTyinhWHwmITO7vrvPEG jTf7bKxqO7W0B4etxjRa9cwSqSwudK5DNviA1TxY6G7HPXZgByqSXpyOXGA2dM+kh9QPh1o8ixRbo mUVkncHCYo/8vq8i4Uuo5AcDnAmL2dsT+zcuWyMHZXRgDu4SpJpJ1lOUxeVmrEYFrcDnxGJpzMrAj 9LfbcRg0jA0Zvz6CEMFMUTTapjB38d0IoDX2A9OuvhmQk+Gfbzqs4u6uFNIApAwwG2UR8NtTV/5YY Fvsuw0Qg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1smFNj-0000000983J-0x4T; Thu, 05 Sep 2024 16:30:51 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1smFKe-0000000974j-2rX8 for linux-arm-kernel@lists.infradead.org; Thu, 05 Sep 2024 16:27:41 +0000 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 9F38CFEC; Thu, 5 Sep 2024 09:28:06 -0700 (PDT) Received: from [10.1.196.40] (e121345-lin.cambridge.arm.com [10.1.196.40]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 836863F73B; Thu, 5 Sep 2024 09:27:32 -0700 (PDT) Message-ID: <53f13813-a515-475a-836d-0b6017a117eb@arm.com> Date: Thu, 5 Sep 2024 17:27:28 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] Revert "iommu/io-pgtable-arm: Optimise non-coherent unmap" To: Will Deacon , Rob Clark Cc: iommu@lists.linux.dev, linux-arm-msm@vger.kernel.org, freedreno@lists.freedesktop.org, Ashish Mhetre , Rob Clark , Joerg Roedel , "moderated list:ARM SMMU DRIVERS" , open list References: <20240905124956.84932-1-robdclark@gmail.com> <20240905155330.GA15246@willie-the-truck> From: Robin Murphy Content-Language: en-GB In-Reply-To: <20240905155330.GA15246@willie-the-truck> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240905_092740_797861_C1DAB1C0 X-CRM114-Status: GOOD ( 22.98 ) 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 05/09/2024 4:53 pm, Will Deacon wrote: > Hi Rob, > > On Thu, Sep 05, 2024 at 05:49:56AM -0700, Rob Clark wrote: >> From: Rob Clark >> >> This reverts commit 85b715a334583488ad7fbd3001fe6fd617b7d4c0. >> >> It was causing gpu smmu faults on x1e80100. >> >> I _think_ what is causing this is the change in ordering of >> __arm_lpae_clear_pte() (dma_sync_single_for_device() on the pgtable >> memory) and io_pgtable_tlb_flush_walk(). I'm not entirely sure how >> this patch is supposed to work correctly in the face of other >> concurrent translations (to buffers unrelated to the one being >> unmapped(), because after the io_pgtable_tlb_flush_walk() we can have >> stale data read back into the tlb. >> >> Signed-off-by: Rob Clark >> --- >> drivers/iommu/io-pgtable-arm.c | 31 ++++++++++++++----------------- >> 1 file changed, 14 insertions(+), 17 deletions(-) > > Please can you try the diff below, instead? Given that the GPU driver's .tlb_add_page is a no-op, I can't see this making a difference. In fact, given that msm_iommu_pagetable_unmap() still does a brute-force iommu_flush_iotlb_all() after io-pgtable returns, and in fact only recently made .tlb_flush_walk start doing anything either for the sake of the map path, I'm now really wondering how this patch has had any effect at all... :/ > > Will > > --->8 > > diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c > index 0e67f1721a3d..0a32e9499e2c 100644 > --- a/drivers/iommu/io-pgtable-arm.c > +++ b/drivers/iommu/io-pgtable-arm.c > @@ -672,7 +672,7 @@ static size_t __arm_lpae_unmap(struct arm_lpae_io_pgtable *data, > /* Clear the remaining entries */ > __arm_lpae_clear_pte(ptep, &iop->cfg, i); > > - if (gather && !iommu_iotlb_gather_queued(gather)) > + if (!iommu_iotlb_gather_queued(gather)) Note that this would reintroduce the latent issue which was present originally, wherein iommu_iotlb_gather_queued(NULL) is false, but if we actually allow a NULL gather to be passed to io_pgtable_tlb_add_page() it may end up being dereferenced (e.g. in arm-smmu-v3). Thanks, Robin. > for (int j = 0; j < i; j++) > io_pgtable_tlb_add_page(iop, gather, iova + j * size, size); >