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 D86C8C71130 for ; Mon, 7 Jul 2025 19:06:58 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id A1D8F10E52F; Mon, 7 Jul 2025 19:06:58 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.b="t4NObD3O"; dkim-atps=neutral Received: from nyc.source.kernel.org (nyc.source.kernel.org [147.75.193.91]) by gabe.freedesktop.org (Postfix) with ESMTPS id 7831110E52F; Mon, 7 Jul 2025 19:06:57 +0000 (UTC) Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by nyc.source.kernel.org (Postfix) with ESMTP id 9A62BA54312; Mon, 7 Jul 2025 19:06:56 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0534EC4CEE3; Mon, 7 Jul 2025 19:06:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1751915216; bh=c5ydvdpNmmS/uIC1z+YD+lCe1xruHbZRmDzLrfPGm0c=; h=Date:Subject:Cc:To:From:References:In-Reply-To:From; b=t4NObD3OZGoVszdgOqabwHh/3ZRSpEnEwPQB5i2yPvXaF9MquceFGRrwSndhrFRY/ yC5qZ9v+8Baqe0UlV3Fvw6SgduxU9a4TdShe+5kM8saS2ROuq/H0UPsFHBdPjn96qn GAojgpAce0Maty1SmSNtZV87nW/hzM504udrdUYXNJ0cMQv/OK5xxHzJr2OdXDPGdk NI1SKviU0dMSsN+MD8qnjOcUSFn3YYxWqEngtv6WdKTHb/ZhkrT3NzPIfCdBpkwiAL RkXZ61Y0DFU2NJYk5I275h2SihKv+qgeqDZ9HTT+pO1u2FzMQdOGdqUgzu7tEOoS7L YZjDVYfj9APxw== Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Mon, 07 Jul 2025 21:06:50 +0200 Message-Id: Subject: Re: [PATCH v4 4/7] drm/gpuvm: Add a helper to check if two VA can be merged Cc: "Caterina Shablia" , "Maarten Lankhorst" , "Maxime Ripard" , "Thomas Zimmermann" , "David Airlie" , "Simona Vetter" , "Frank Binns" , "Matt Coster" , "Karol Herbst" , "Lyude Paul" , "Boris Brezillon" , "Steven Price" , "Liviu Dudau" , "Lucas De Marchi" , =?utf-8?q?Thomas_Hellstr=C3=B6m?= , "Rodrigo Vivi" , , , , , , "Asahi Lina" To: "Danilo Krummrich" From: "Danilo Krummrich" References: <20250707170442.1437009-1-caterina.shablia@collabora.com> <20250707170442.1437009-5-caterina.shablia@collabora.com> In-Reply-To: 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" On Mon Jul 7, 2025 at 9:00 PM CEST, Danilo Krummrich wrote: > On Mon Jul 7, 2025 at 7:04 PM CEST, Caterina Shablia wrote: >> diff --git a/drivers/gpu/drm/drm_gpuvm.c b/drivers/gpu/drm/drm_gpuvm.c >> index 05978c5c38b1..dc3c2f906400 100644 >> --- a/drivers/gpu/drm/drm_gpuvm.c >> +++ b/drivers/gpu/drm/drm_gpuvm.c >> @@ -2098,12 +2098,48 @@ op_unmap_cb(const struct drm_gpuvm_ops *fn, void= *priv, >> return fn->sm_step_unmap(&op, priv); >> } >> =20 >> +static bool can_merge(struct drm_gpuvm *gpuvm, const struct drm_gpuva *= a, >> + const struct drm_gpuva *b) >> +{ >> + /* Only GEM-based mappings can be merged, and they must point to >> + * the same GEM object. >> + */ >> + if (a->gem.obj !=3D b->gem.obj || !a->gem.obj) >> + return false; >> + >> + /* Let's keep things simple for now and force all flags to match. */ >> + if (a->flags !=3D b->flags) >> + return false; Forgot to mention, this can include driver specific flags. How do we know f= rom the generic code whether this condition makes sense? *At least* it would ne= ed to be documented. However, I think it would be better to provide an optional callback for dri= vers to check whether merge makes sense or not. This doesn't mean we need driver= s to do those common checks, this can remain here in the common code. >> + >> + /* Order VAs for the rest of the checks. */ >> + if (a->va.addr > b->va.addr) >> + swap(a, b); >> + >> + /* We assume the caller already checked that VAs overlap or are >> + * contiguous. >> + */ >> + if (drm_WARN_ON(gpuvm->drm, b->va.addr > a->va.addr + a->va.range)) >> + return false; >> + >> + /* We intentionally ignore u64 underflows because all we care about >> + * here is whether the VA diff matches the GEM offset diff. >> + */ >> + return b->va.addr - a->va.addr =3D=3D b->gem.offset - a->gem.offset; >> +} >> + >> static int >> __drm_gpuvm_sm_map(struct drm_gpuvm *gpuvm, >> const struct drm_gpuvm_ops *ops, void *priv, >> const struct drm_gpuvm_map_req *req) >> { >> struct drm_gpuva *va, *next; >> + struct drm_gpuva reqva =3D { >> + .va.addr =3D req->va.addr, >> + .va.range =3D req->va.range, >> + .gem.offset =3D req->gem.offset, >> + .gem.obj =3D req->gem.obj, >> + .flags =3D req->flags, > > Huh? Where does req->flags come from? I don't remember that this flag exi= sts in > struct drm_gpuvm_map_req in the preceding patch? > >> + }; >> u64 req_end =3D req->va.addr + req->va.range; >> int ret; >> =20 >> @@ -2116,12 +2152,9 @@ __drm_gpuvm_sm_map(struct drm_gpuvm *gpuvm, >> u64 addr =3D va->va.addr; >> u64 range =3D va->va.range; >> u64 end =3D addr + range; >> - bool merge =3D !!va->gem.obj; >> + bool merge =3D can_merge(gpuvm, va, &reqva); > > I know you want to do the swap() trick above, but I don't like creating a > temporary struct drm_gpuva with all the other uninitialized fields. > > If you really want this, can we please limit the scope? Maybe the followi= ng > helper: > > static bool can_merge(struct drm_gpuvm *gpuvm, > const struct drm_gpuva *va, > struct drm_gpuvm_map_req *req) > { > struct drm_gpuva reqva =3D { ... }; > return __can_merge(gpuvm, va, reqva); > }