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Tue, 11 Aug 2026 07:29:13 -0700 (PDT) From: Zhenhao Wan Date: Tue, 11 Aug 2026 22:28:50 +0800 Subject: [PATCH 1/2] drm/nouveau/dmem: fix mismatched DMA unmap size for large folios Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260811-b4-nouveau-dmem-thp-fixes-v1-1-2cdf9860af2a@gmail.com> References: <20260811-b4-nouveau-dmem-thp-fixes-v1-0-2cdf9860af2a@gmail.com> In-Reply-To: <20260811-b4-nouveau-dmem-thp-fixes-v1-0-2cdf9860af2a@gmail.com> To: Lyude Paul , Danilo Krummrich , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Andrew Morton , Balbir Singh Cc: dri-devel@lists.freedesktop.org, nouveau@lists.freedesktop.org, linux-kernel@vger.kernel.org, Zhenhao Wan , Yuhao Jiang , stable@vger.kernel.org X-Mailer: b4 0.15.2 X-Developer-Signature: v=1; a=ed25519-sha256; t=1786458544; l=1970; i=whi4ed0g@gmail.com; h=from:subject:message-id; bh=Ms56ytpwHSeFHdp6KwntU4e11PGxIQxSST+kpBvVKeU=; b=J5mecMWmZ3choz70xb/rBRDm8mbs+xBBy0WtROvpD9chGghI1Y9qX2K3DiSCMBIRSYRdUvbwn J4w19x36HDnAC44CAx0r8knwMUTbJhDgWQGJ/Qk8KO7+ukM2tsSaLMa X-Developer-Key: i=whi4ed0g@gmail.com; a=ed25519; pk=zRTKlstE0LmilshGwJsFYEVjiT6RiXMBXK8Og6VmuVQ= Device-private THP migration maps migration buffers with page_size() and records that length in dma_info->size. For a compound folio page_size() is PAGE_SIZE << order, but two teardown sites still pass a literal PAGE_SIZE to dma_unmap_page(): - nouveau_dmem_migrate_to_ram() on the success path, and - nouveau_dmem_migrate_copy_one() on the copy-error path. For an order > 0 folio this unmaps less than was mapped, leaking the remainder of the IOMMU/IOVA mapping. The other unmap sites, in nouveau_dmem_migrate_chunk() and nouveau_dmem_evict_chunk(), already use the saved size; use it here too. Fixes: c32287471077 ("gpu/drm/nouveau: enable THP support for GPU memory mi= gration") Reported-by: Yuhao Jiang Assisted-by: Claude:claude-opus-5 Cc: stable@vger.kernel.org Signed-off-by: Zhenhao Wan --- drivers/gpu/drm/nouveau/nouveau_dmem.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/nouveau/nouveau_dmem.c b/drivers/gpu/drm/nouve= au/nouveau_dmem.c index 9442ec6e1f6c..d2abee3efb9a 100644 --- a/drivers/gpu/drm/nouveau/nouveau_dmem.c +++ b/drivers/gpu/drm/nouveau/nouveau_dmem.c @@ -267,7 +267,7 @@ static vm_fault_t nouveau_dmem_migrate_to_ram(struct vm= _fault *vmf) nouveau_fence_new(&fence, dmem->migrate.chan); migrate_vma_pages(&args); nouveau_dmem_fence_done(&fence); - dma_unmap_page(drm->dev->dev, dma_info.dma_addr, PAGE_SIZE, + dma_unmap_page(drm->dev->dev, dma_info.dma_addr, dma_info.size, DMA_BIDIRECTIONAL); done: migrate_vma_finalize(&args); @@ -772,7 +772,7 @@ static unsigned long nouveau_dmem_migrate_copy_one(stru= ct nouveau_drm *drm, return mpfn; =20 out_dma_unmap: - dma_unmap_page(dev, dma_info->dma_addr, PAGE_SIZE, DMA_BIDIRECTIONAL); + dma_unmap_page(dev, dma_info->dma_addr, dma_info->size, DMA_BIDIRECTIONAL= ); out_free_page: nouveau_dmem_page_free_locked(drm, dpage); out: --=20 2.34.1 From nobody Tue Sep 29 06:11:03 2026 Received: from mail-pf1-f178.google.com (mail-pf1-f178.google.com [209.85.210.178]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 87C40263C8F for ; Tue, 11 Aug 2026 14:29:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.178 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786458560; cv=none; b=RBQ9fUCE5BKyYxgKcImy33PRwIMhhFfzgh5oyjM5N59oX9ec7tCYZ4QtUPvLaNTYnGNoB1nUI7Q/8ADm6C00phZN+pospKh5zbTzNSKfzDHSg0GH4uyRav4XB0QvxLkIklA1kZNab0lz69j0ZEfzgcjl9mfa58bzzDX3UVENw8k= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; 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Tue, 11 Aug 2026 07:29:18 -0700 (PDT) Received: from LAPTOP-N3B6U5LC.localdomain ([117.147.100.52]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-84fa954fc8asm890209b3a.50.2026.08.11.07.29.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 11 Aug 2026 07:29:18 -0700 (PDT) From: Zhenhao Wan Date: Tue, 11 Aug 2026 22:28:51 +0800 Subject: [PATCH 2/2] drm/nouveau/dmem: fix callocated underflow on large folio split Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260811-b4-nouveau-dmem-thp-fixes-v1-2-2cdf9860af2a@gmail.com> References: <20260811-b4-nouveau-dmem-thp-fixes-v1-0-2cdf9860af2a@gmail.com> In-Reply-To: <20260811-b4-nouveau-dmem-thp-fixes-v1-0-2cdf9860af2a@gmail.com> To: Lyude Paul , Danilo Krummrich , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Andrew Morton , Balbir Singh Cc: dri-devel@lists.freedesktop.org, nouveau@lists.freedesktop.org, linux-kernel@vger.kernel.org, Zhenhao Wan , Yuhao Jiang , stable@vger.kernel.org X-Mailer: b4 0.15.2 X-Developer-Signature: v=1; a=ed25519-sha256; t=1786458544; l=2343; i=whi4ed0g@gmail.com; h=from:subject:message-id; bh=25RfUnYCCAn500NPErkFHuNL6+Q3MhhwJRPB178c5V4=; b=KuT7Vz44ftGEbyMSNmyMs8gTFuhkVAnAk7FcqfCULSkaKx7+Tre0AqjyKJ+yRD05IFx+yF++P mhFHY/fO+knCTMRcui6xM+5LBLSBox31ZOFlheXXru87VbNIRBncJX0 X-Developer-Key: i=whi4ed0g@gmail.com; a=ed25519; pk=zRTKlstE0LmilshGwJsFYEVjiT6RiXMBXK8Og6VmuVQ= nouveau_dmem_folio_free() drops chunk->callocated once per freed folio, while a large (compound) device-private folio is only counted once when it is allocated. When such a folio is split, the mm core invokes ->folio_split() (nouveau_dmem_folio_split()) once for each new sub-folio, but the hook only fixes up the sub-folio metadata and leaves chunk->callocated unchanged. Each resulting sub-folio is later freed separately, so after a split the single allocation (+1) is met by N frees (-N), leaving chunk->callocated short by N-1. On the first split/free cycle it underflows: WARN_ON(!chunk->callocated) fires, the unsigned counter wraps and never returns to zero, so the chunk can no longer be reclaimed (nouveau_dmem_fini() also warns on the leaked count). Account for the new sub-folio in the split hook, under the same lock as nouveau_dmem_folio_free(), so the count stays balanced. Fixes: c32287471077 ("gpu/drm/nouveau: enable THP support for GPU memory mi= gration") Reported-by: Yuhao Jiang Assisted-by: Claude:claude-opus-5 Cc: stable@vger.kernel.org Signed-off-by: Zhenhao Wan Reviewed-by: Lyude Paul --- drivers/gpu/drm/nouveau/nouveau_dmem.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/drivers/gpu/drm/nouveau/nouveau_dmem.c b/drivers/gpu/drm/nouve= au/nouveau_dmem.c index d2abee3efb9a..ad4570c50be7 100644 --- a/drivers/gpu/drm/nouveau/nouveau_dmem.c +++ b/drivers/gpu/drm/nouveau/nouveau_dmem.c @@ -279,11 +279,25 @@ static vm_fault_t nouveau_dmem_migrate_to_ram(struct = vm_fault *vmf) =20 static void nouveau_dmem_folio_split(struct folio *head, struct folio *tai= l) { + struct nouveau_dmem_chunk *chunk; + struct nouveau_dmem *dmem; + if (tail =3D=3D NULL) return; tail->pgmap =3D head->pgmap; tail->mapping =3D head->mapping; folio_set_zone_device_data(tail, folio_zone_device_data(head)); + + /* + * The split hands out a new independently-freeable folio that will + * later be released via nouveau_dmem_folio_free(); account for it so + * chunk->callocated stays balanced. + */ + chunk =3D nouveau_page_to_chunk(&head->page); + dmem =3D chunk->drm->dmem; + spin_lock(&dmem->lock); + chunk->callocated++; + spin_unlock(&dmem->lock); } =20 static const struct dev_pagemap_ops nouveau_dmem_pagemap_ops =3D { --=20 2.34.1