From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5F3E5277037 for ; Thu, 23 Oct 2025 21:27:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761254834; cv=none; b=em+TiQe19O3zzNh4p45GLErt3/8V/kQ+We7F4geAcncrGXqsRxbRGf4+P4DNCIN+Lb+Q3mEfoISCc5YfLq4VburjNjC5UecQaGHc9EP9iwuQRpB+8r3WziYuDPPiuYIqQhB0tKL6Zduy8ssH3fZeK995DKTZdQDChjWzENNts1o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761254834; c=relaxed/simple; bh=qf6a23PTN6BJbtTf8XRrDB2SB4SFxvK4SN0a7l+wXvs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=UGAsydLR3tNlzEEnN7TDcWy9NIjj1SuVtuiP3FzJDZyqCn56fkpCGsK3w+VDBhjZFSCO3TlP5leolKyjVU5ZvJbBYXcB8IobI2Dpm5dzel1o0umKnac1FvaJN3L8vBdz8U8fCOjt3/sEhbOrOQINNkxw9OFvHX+QpMRewibbnc0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=NT8SbYPR; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="NT8SbYPR" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1761254831; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=fgB8Z93TRo4WCd3p++Pa+dxvLDuIIdiTgas1fg3xpX4=; b=NT8SbYPRYA9v9J7dKNK4AZ8h78wGV+8eG/G/D78qzzpxRKizhpGtJROf1IQbietltPPpvr t9LihVvifoZXjEbgB6+NHLumnaJGwzRA8cMUBEaZUi/nLPkaqQ2DB2ULOTmvDPhdsYRG+A Om0u9opXo9x36ZPy12pVqt9dAXkgCRM= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-108-DM6r9jKOOTedqlgtO7uMLQ-1; Thu, 23 Oct 2025 17:27:05 -0400 X-MC-Unique: DM6r9jKOOTedqlgtO7uMLQ-1 X-Mimecast-MFC-AGG-ID: DM6r9jKOOTedqlgtO7uMLQ_1761254823 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 28A701956046; Thu, 23 Oct 2025 21:27:03 +0000 (UTC) Received: from chopper.lan (unknown [10.22.64.235]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id CC7A730002DB; Thu, 23 Oct 2025 21:26:59 +0000 (UTC) From: Lyude Paul To: dri-devel@lists.freedesktop.org, rust-for-linux@vger.kernel.org, Alice Ryhl , Daniel Almeida , Danilo Krummrich , linux-kernel@vger.kernel.org Cc: David Airlie , Simona Vetter , Miguel Ojeda , Alex Gaynor , Boqun Feng , Gary Guo , =?UTF-8?q?Bj=C3=B6rn=20Roy=20Baron?= , Benno Lossin , Andreas Hindborg , Trevor Gross , Asahi Lina Subject: [PATCH v5 8/8] rust: drm/gem: Add vmap functions to shmem bindings Date: Thu, 23 Oct 2025 17:22:10 -0400 Message-ID: <20251023212540.1141999-9-lyude@redhat.com> In-Reply-To: <20251023212540.1141999-1-lyude@redhat.com> References: <20251023212540.1141999-1-lyude@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 One of the more obvious use cases for gem shmem objects is the ability to create mappings into their contents, specifically iosys mappings. Now that we've added iosys_map rust bindings to the kernel, let's hook these up in gem shmem. Similar to how we handle SGTables, we make sure there's two different types of mappings: owned mappings (kernel::drm::gem::shmem::VMap) and borrowed mappings (kernel::drm::gem::shmem::VMapRef). One last note: we change the #[expect(unused)] for RawIoSysMap::from_raw() to an #[allow(unused)]. Normally we would simply remove the lint assertion, however - since shmem is conditionally built, we need allow to avoid hitting warnings in certain kernel configurations. Signed-off-by: Lyude Paul --- rust/kernel/drm/gem/shmem.rs | 160 ++++++++++++++++++++++++++++++++++- rust/kernel/iosys_map.rs | 2 +- 2 files changed, 160 insertions(+), 2 deletions(-) diff --git a/rust/kernel/drm/gem/shmem.rs b/rust/kernel/drm/gem/shmem.rs index 21ccb6c1824be..62a2c12b9fe2a 100644 --- a/rust/kernel/drm/gem/shmem.rs +++ b/rust/kernel/drm/gem/shmem.rs @@ -13,15 +13,18 @@ container_of, drm::{device, driver, gem, private::Sealed}, error::{from_err_ptr, to_result}, + iosys_map::*, prelude::*, scatterlist, + transmute::*, types::{ARef, Opaque}, }; use core::{ + mem::{self, MaybeUninit}, ops::{Deref, DerefMut}, ptr::NonNull, }; -use gem::{BaseObjectPrivate, DriverObject, IntoGEMObject}; +use gem::{BaseObject, BaseObjectPrivate, DriverObject, IntoGEMObject}; /// A struct for controlling the creation of shmem-backed GEM objects. /// @@ -192,6 +195,72 @@ pub fn owned_sg_table(&self) -> Result> { _owner: self.into(), }) } + + /// Attempt to create a [`RawIoSysMap`] from the gem object. + fn raw_vmap(&self) -> Result> { + build_assert!( + mem::size_of::() > 0, + "It doesn't make sense for the mapping type to be a ZST" + ); + + let mut map: MaybeUninit = MaybeUninit::uninit(); + + // SAFETY: drm_gem_shmem_vmap can be called with the DMA reservation lock held + to_result(unsafe { + // TODO: see top of file + bindings::dma_resv_lock(self.raw_dma_resv(), core::ptr::null_mut()); + let ret = bindings::drm_gem_shmem_vmap_locked(self.as_shmem(), map.as_mut_ptr()); + bindings::dma_resv_unlock(self.raw_dma_resv()); + ret + })?; + + // SAFETY: if drm_gem_shmem_vmap did not fail, map is initialized now + Ok(unsafe { RawIoSysMap::from_raw(map.assume_init()) }) + } + + /// Unmap a [`RawIoSysMap`] from the gem object. + /// + /// # Safety + /// + /// - The caller promises that `map` came from a prior call to [`Self::raw_vmap`] on this gem + /// object. + /// - The caller promises that the memory pointed to by `map` will no longer be accesed through + /// this instance. + unsafe fn raw_vunmap(&self, map: &mut RawIoSysMap) { + let resv = self.raw_dma_resv(); + + // SAFETY: + // - This function is safe to call with the DMA reservation lock held + // - Our `ARef` is proof that the underlying gem object here is initialized and thus safe to + // dereference. + unsafe { + // TODO: see top of file + bindings::dma_resv_lock(resv, core::ptr::null_mut()); + bindings::drm_gem_shmem_vunmap_locked(self.as_shmem(), map.as_raw_mut()); + bindings::dma_resv_unlock(resv); + } + } + + /// Creates and returns a virtual kernel memory mapping for this object. + pub fn vmap(&self) -> Result> { + let map = self.raw_vmap()?; + + Ok(VMapRef { + // SAFETY: + // - The size of the vmap is the same as the size of the gem + // - The vmap will remain alive until this object is dropped. + map: unsafe { IoSysMapRef::new(map, self.size()) }, + owner: self, + }) + } + + /// Creates and returns an owned reference to a virtual kernel memory mapping for this object. + pub fn owned_vmap(&self) -> Result> { + Ok(VMap { + map: self.raw_vmap()?, + owner: self.into(), + }) + } } impl Deref for Object { @@ -243,6 +312,95 @@ impl driver::AllocImpl for Object { }; } +/// A borrowed reference to a virtual mapping for a shmem-based GEM object in kernel address space. +pub struct VMapRef<'a, D: DriverObject, T: AsBytes + FromBytes> { + map: IoSysMapRef<'a, T>, + owner: &'a Object, +} + +impl<'a, D: DriverObject, T: AsBytes + FromBytes> Clone for VMapRef<'a, D, T> { + fn clone(&self) -> Self { + // SAFETY: We have a successful vmap already, so this can't fail + unsafe { self.owner.vmap().unwrap_unchecked() } + } +} + +impl<'a, D: DriverObject, T: AsBytes + FromBytes> Deref for VMapRef<'a, D, T> { + type Target = IoSysMapRef<'a, T>; + + fn deref(&self) -> &Self::Target { + &self.map + } +} + +impl<'a, D: DriverObject, T: AsBytes + FromBytes> DerefMut for VMapRef<'a, D, T> { + fn deref_mut(&mut self) -> &mut Self::Target { + &mut self.map + } +} + +impl<'a, D: DriverObject, T: AsBytes + FromBytes> Drop for VMapRef<'a, D, T> { + fn drop(&mut self) { + // SAFETY: Our existence is proof that this map was previously created using self.owner. + unsafe { self.owner.raw_vunmap(&mut self.map) }; + } +} + +/// An owned reference to a virtual mapping for a shmem-based GEM object in kernel address space. +/// +/// # Invariants +/// +/// - The memory pointed to by `map` is at least as large as `T`. +/// - The memory pointed to by `map` remains valid at least until this object is dropped. +pub struct VMap { + map: RawIoSysMap, + owner: ARef>, +} + +impl Clone for VMap { + fn clone(&self) -> Self { + // SAFETY: We have a successful vmap already, so this can't fail + unsafe { self.owner.owned_vmap().unwrap_unchecked() } + } +} + +impl<'a, D: DriverObject, T: AsBytes + FromBytes> From> for VMap { + fn from(value: VMapRef<'a, D, T>) -> Self { + let this = Self { + map: value.map.clone(), + owner: value.owner.into(), + }; + + mem::forget(value); + this + } +} + +impl VMap { + /// Return a reference to the iosys map for this `VMap`. + pub fn get(&self) -> IoSysMapRef<'_, T> { + // SAFETY: The size of the iosys_map is equivalent to the size of the gem object. + unsafe { IoSysMapRef::new(self.map.clone(), self.owner.size()) } + } + + /// Borrows a reference to the object that owns this virtual mapping. + pub fn owner(&self) -> &Object { + &self.owner + } +} + +impl Drop for VMap { + fn drop(&mut self) { + // SAFETY: Our existence is proof that this map was previously created using self.owner + unsafe { self.owner.raw_vunmap(&mut self.map) }; + } +} + +/// SAFETY: `iosys_map` objects are safe to send across threads. +unsafe impl Send for VMap {} +/// SAFETY: `iosys_map` objects are safe to send across threads. +unsafe impl Sync for VMap {} + /// An owned reference to a scatter-gather table of DMA address spans for a GEM shmem object. /// /// This object holds an owned reference to the underlying GEM shmem object, ensuring that the diff --git a/rust/kernel/iosys_map.rs b/rust/kernel/iosys_map.rs index 4da0ab57cf35c..e7540139ada01 100644 --- a/rust/kernel/iosys_map.rs +++ b/rust/kernel/iosys_map.rs @@ -32,7 +32,7 @@ impl RawIoSysMap { /// Convert from a raw `bindings::iosys_map`. - #[expect(unused)] + #[allow(unused)] #[inline] pub(crate) fn from_raw(val: bindings::iosys_map) -> Self { Self(val, PhantomData) -- 2.51.0