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 7AC3BCFA76C for ; Fri, 21 Nov 2025 10:19:37 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 3E3C610E84D; Fri, 21 Nov 2025 10:19:37 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.b="mGdd3on0"; dkim-atps=neutral Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.21]) by gabe.freedesktop.org (Postfix) with ESMTPS id 820B210E849; Fri, 21 Nov 2025 10:19:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1763720376; x=1795256376; h=message-id:subject:from:to:cc:date:in-reply-to: references:content-transfer-encoding:mime-version; bh=ImYrT4ezOGbF3CP/zqe9wmHgOUPHDvbUTkb7IowfDTc=; b=mGdd3on0/UPJb3LIISkNAaQThucODjpGQv05nj4OpMloWD9kaGzhPJ7c uX9rLZXkwPZ9YooiKtg1bwqx5VfBl0Td1yoKGV5RZl0nuNl8jFA6CVsEA 8xyMAg++tfQZoGgINF6dFAx348y0Lx7mDNDFluExDUxcH8oYv3MbDVnee bUp2T52X0DwJM1B1LyxkuY+MJqHnBPGNYNoMJRZJlTFyTQv8arRgu1V5a ALP8wTgBJ3pTDLPmT/yUdrNteplClVfiDgT3X0xYAmuQ3SVjURbZt2Sro xFaVYQxmNwsBXntT8Gk01fSmAoKr9Wl1h7e42MCqYrQ4Nh8EUhfEW1F0v Q==; X-CSE-ConnectionGUID: wDIzIBhUQ+K8lyBidU/XFw== X-CSE-MsgGUID: YShc3l6bRXuJztx0HAP1JQ== X-IronPort-AV: E=McAfee;i="6800,10657,11619"; a="65744814" X-IronPort-AV: E=Sophos;i="6.20,215,1758610800"; d="scan'208";a="65744814" Received: from orviesa009.jf.intel.com ([10.64.159.149]) by orvoesa113.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Nov 2025 02:19:35 -0800 X-CSE-ConnectionGUID: qe5RUukAT6mmyZcI9/lB2w== X-CSE-MsgGUID: uOkXJz9ZTtKONrRjsswzDQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.20,215,1758610800"; d="scan'208";a="191448644" Received: from klitkey1-mobl1.ger.corp.intel.com (HELO [10.245.245.9]) ([10.245.245.9]) by orviesa009-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Nov 2025 02:19:31 -0800 Message-ID: Subject: Re: [PATCH v2 02/17] drm/pagemap, drm/xe: Add refcounting to struct drm_pagemap From: Thomas =?ISO-8859-1?Q?Hellstr=F6m?= To: "Ghimiray, Himal Prasad" , intel-xe@lists.freedesktop.org Cc: Matthew Brost , dri-devel@lists.freedesktop.org, apopple@nvidia.com, airlied@gmail.com, Simona Vetter , felix.kuehling@amd.com, Christian =?ISO-8859-1?Q?K=F6nig?= , dakr@kernel.org, "Mrozek, Michal" , Joonas Lahtinen Date: Fri, 21 Nov 2025 11:19:29 +0100 In-Reply-To: References: <20251111164408.113070-1-thomas.hellstrom@linux.intel.com> <20251111164408.113070-3-thomas.hellstrom@linux.intel.com> Organization: Intel Sweden AB, Registration Number: 556189-6027 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.54.3 (3.54.3-2.fc41) MIME-Version: 1.0 X-BeenThere: intel-xe@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel Xe graphics driver List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-xe-bounces@lists.freedesktop.org Sender: "Intel-xe" Hi, Himal! On Wed, 2025-11-12 at 11:37 +0530, Ghimiray, Himal Prasad wrote: >=20 >=20 > On 11-11-2025 22:13, Thomas Hellstr=C3=B6m wrote: > > With the end goal of being able to free unused pagemaps > > and allocate them on demand, add a refcount to struct drm_pagemap, > > remove the xe embedded drm_pagemap, allocating and freeing it > > explicitly. > >=20 > > v2: > > - Make the drm_pagemap pointer in drm_gpusvm_pages reference- > > counted. > >=20 > > Signed-off-by: Thomas Hellstr=C3=B6m > > Reviewed-by: Matthew Brost #v1 > > --- > > =C2=A0 drivers/gpu/drm/drm_gpusvm.c=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= |=C2=A0 4 ++- > > =C2=A0 drivers/gpu/drm/drm_pagemap.c=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 | 51 > > ++++++++++++++++++++++++++++++ > > =C2=A0 drivers/gpu/drm/xe/xe_svm.c=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0 | 26 ++++++++++----- > > =C2=A0 drivers/gpu/drm/xe/xe_vram_types.h |=C2=A0 2 +- > > =C2=A0 include/drm/drm_pagemap.h=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0 | 36 +++++++++++++++++++++ > > =C2=A0 5 files changed, 109 insertions(+), 10 deletions(-) > >=20 > > diff --git a/drivers/gpu/drm/drm_gpusvm.c > > b/drivers/gpu/drm/drm_gpusvm.c > > index 73e550c8ff8c..1f96375d1f2b 100644 > > --- a/drivers/gpu/drm/drm_gpusvm.c > > +++ b/drivers/gpu/drm/drm_gpusvm.c > > @@ -1038,6 +1038,7 @@ static void __drm_gpusvm_unmap_pages(struct > > drm_gpusvm *gpusvm, > > =C2=A0=C2=A0 flags.has_dma_mapping =3D false; > > =C2=A0=C2=A0 WRITE_ONCE(svm_pages->flags.__flags, > > flags.__flags); > > =C2=A0=20 > > + drm_pagemap_put(svm_pages->dpagemap); > > =C2=A0=C2=A0 svm_pages->dpagemap =3D NULL; > > =C2=A0=C2=A0 } > > =C2=A0 } > > @@ -1431,7 +1432,8 @@ int drm_gpusvm_get_pages(struct drm_gpusvm > > *gpusvm, > > =C2=A0=20 > > =C2=A0=C2=A0 if (pagemap) { > > =C2=A0=C2=A0 flags.has_devmem_pages =3D true; > > - svm_pages->dpagemap =3D dpagemap; > > + drm_pagemap_put(svm_pages->dpagemap); >=20 > Dont we risk a UAF for dpagemap if svm_pages->dpagemap is same as > dpagemap ? Thanks for reviewing. Here the dpagemap refcount is protected from dropping to zero by a page presence in the CPU address space and us holding the notifier lock. But agree that this looks bad from a reader's perspective. I'll fix that up. Thanks, Thomas