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 D8311D149CD for ; Fri, 25 Oct 2024 17:19:55 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 5145E10EB4F; Fri, 25 Oct 2024 17:19:55 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (1024-bit key; unprotected) header.d=linux.dev header.i=@linux.dev header.b="c9GGxZXT"; dkim-atps=neutral Received: from out-179.mta0.migadu.com (out-179.mta0.migadu.com [91.218.175.179]) by gabe.freedesktop.org (Postfix) with ESMTPS id 782F210EB4F for ; Fri, 25 Oct 2024 17:19:52 +0000 (UTC) Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1729876790; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=zT8cxh9uxcPpAXeRpOz4K99RVMk98+LQB2m+38sDL18=; b=c9GGxZXTqKq/17PPlPsVMWRapDMJVqwydDYWu2ns/FLqowPdC7ORXzFoI+zJd7C8TDSLir Lj4PH0liZOkEAFW/6AzRORJmkXklKHv2BOBZ7KmK3KPsj+xiO8Akx1wdYUIvqi5/D+MoyA PtGgM1V404IJCS5GcRToxe82udFBhOc= Date: Sat, 26 Oct 2024 01:19:42 +0800 MIME-Version: 1.0 Subject: Re: [PATCH 2/3] drm/etnaviv: Map and unmap the GPU VA range with respect to its user size To: Lucas Stach , Russell King , Christian Gmeiner Cc: David Airlie , Simona Vetter , etnaviv@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org References: <20241004194207.1013744-1-sui.jingfeng@linux.dev> <20241004194207.1013744-3-sui.jingfeng@linux.dev> <13b9c1bde7f0534f7f3c576126def206bdafd60c.camel@pengutronix.de> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Sui Jingfeng In-Reply-To: <13b9c1bde7f0534f7f3c576126def206bdafd60c.camel@pengutronix.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT 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" Hi, On 2024/10/7 18:17, Lucas Stach wrote: > Am Samstag, dem 05.10.2024 um 03:42 +0800 schrieb Sui Jingfeng: >> Since the GPU VA space is compact in terms of 4KiB unit, map and/or unmap >> the area that doesn't belong to a context breaks the philosophy of PPAS. >> That results in severe errors: GPU hang and MMU fault (page not present) >> and such. >> >> Shrink the usuable size of etnaviv GEM buffer object to its user size, >> instead of the original physical size of its backing memory. >> >> Signed-off-by: Sui Jingfeng >> --- >> drivers/gpu/drm/etnaviv/etnaviv_mmu.c | 28 +++++++++------------------ >> 1 file changed, 9 insertions(+), 19 deletions(-) >> >> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_mmu.c b/drivers/gpu/drm/etnaviv/etnaviv_mmu.c >> index 6fbc62772d85..a52ec5eb0e3d 100644 >> --- a/drivers/gpu/drm/etnaviv/etnaviv_mmu.c >> +++ b/drivers/gpu/drm/etnaviv/etnaviv_mmu.c >> @@ -70,8 +70,10 @@ static int etnaviv_context_map(struct etnaviv_iommu_context *context, >> } >> >> static int etnaviv_iommu_map(struct etnaviv_iommu_context *context, u32 iova, >> + unsigned int user_len, >> struct sg_table *sgt, int prot) >> -{ struct scatterlist *sg; >> +{ >> + struct scatterlist *sg; >> unsigned int da = iova; >> unsigned int i; >> int ret; >> @@ -81,7 +83,8 @@ static int etnaviv_iommu_map(struct etnaviv_iommu_context *context, u32 iova, >> >> for_each_sgtable_dma_sg(sgt, sg, i) { >> phys_addr_t pa = sg_dma_address(sg) - sg->offset; >> - size_t bytes = sg_dma_len(sg) + sg->offset; >> + unsigned int phys_len = sg_dma_len(sg) + sg->offset; >> + size_t bytes = MIN(phys_len, user_len); >> >> VERB("map[%d]: %08x %pap(%zx)", i, iova, &pa, bytes); >> >> @@ -89,6 +92,7 @@ static int etnaviv_iommu_map(struct etnaviv_iommu_context *context, u32 iova, >> if (ret) >> goto fail; >> >> + user_len -= bytes; >> da += bytes; >> } > Since the MIN(phys_len, user_len) may limit the mapped amount in the > wrong direction, I was thinking that if this will could really happen. 'if (phys_len <= user_len)' is true, the 'bytes' is a number of multiple of PAGE_SIZE. Since our sg table is created by drm_prime_pages_to_sg(), so the program still works exactly some as before. It only differs from previous when 'if (phys_len > user_len)' is true, but then, it is the tail SG entry that the size of it is not a multiple of PAGE_SIZE. The 'bytes' will be *exactly* the size of remain GPUVA range we should map. > I would think it would be good to add a > WARN_ON(user_len != 0) after the dma SG iteration. So the program here seems nearly always correct, no? Or are you means that when the CPU PAGE size < 4KiB cases ? I never ever have a CPU has < 4 KiB page configuration. Regards, Sui >> >> @@ -104,21 +108,7 @@ static int etnaviv_iommu_map(struct etnaviv_iommu_context *context, u32 iova, >> static void etnaviv_iommu_unmap(struct etnaviv_iommu_context *context, u32 iova, >> struct sg_table *sgt, unsigned len) >> { >> - struct scatterlist *sg; >> - unsigned int da = iova; >> - int i; >> - >> - for_each_sgtable_dma_sg(sgt, sg, i) { >> - size_t bytes = sg_dma_len(sg) + sg->offset; >> - >> - etnaviv_context_unmap(context, da, bytes); >> - >> - VERB("unmap[%d]: %08x(%zx)", i, iova, bytes); >> - >> - BUG_ON(!PAGE_ALIGNED(bytes)); >> - >> - da += bytes; >> - } >> + etnaviv_context_unmap(context, iova, len); > This drops some sanity checks, but I have only ever seen them fire when > we had other kernel memory corruption issues, so I'm fine with the > simplification you did here. > > Regards, > Lucas > >> >> context->flush_seq++; >> } >> @@ -131,7 +121,7 @@ static void etnaviv_iommu_remove_mapping(struct etnaviv_iommu_context *context, >> lockdep_assert_held(&context->lock); >> >> etnaviv_iommu_unmap(context, mapping->vram_node.start, >> - etnaviv_obj->sgt, etnaviv_obj->base.size); >> + etnaviv_obj->sgt, etnaviv_obj->user_size); >> drm_mm_remove_node(&mapping->vram_node); >> } >> >> @@ -314,7 +304,7 @@ int etnaviv_iommu_map_gem(struct etnaviv_iommu_context *context, >> goto unlock; >> >> mapping->iova = node->start; >> - ret = etnaviv_iommu_map(context, node->start, sgt, >> + ret = etnaviv_iommu_map(context, node->start, user_size, sgt, >> ETNAVIV_PROT_READ | ETNAVIV_PROT_WRITE); >> >> if (ret < 0) { -- Best regards, Sui