From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 00D9F238C23 for ; Thu, 9 Apr 2026 00:16:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775693799; cv=none; b=fnMJnXbso+cuFxCYWria74IZxrjQfDTkJsUU2dWYZITPGa7bm+Ux4o/2I3HELJkj3Zjw4KBElAf+qtbqnaDZ2OhC5w/DA4wKffIMT9AcPLXa7NC2+HSU6ngKGOAG4ys+87rPD7uq5o/2IHrYfIHZIdMHCha3N+ZTbvbZW7+ZA2Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775693799; c=relaxed/simple; bh=6IXIum0cDL0t1dPq/LH926X9v7QyDHkPIxeerw24UDE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:content-type; b=uVFQgfCRHLb7jODV9HJDQUpQ9hSH2PGy4M5WWsCJBNiAcFY9NmTp/BHNEa29QXRYTS+mjdkSd/hKO/Uq4lhRhVzi4qNR4Y5a0DpLQgimWR6K8APDFn3iZXI0IB7dfAk+VGENH+GWJuBiy1vScYdPYPpciQ1DI5PPTrO2vqTZrVE= 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=Pv4oQDGz; arc=none smtp.client-ip=170.10.129.124 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="Pv4oQDGz" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1775693797; 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=/K+peBcGlE3GY5d6uET5VxMovheiwOxHprQZIawbTV0=; b=Pv4oQDGzTqfDI8C1GPbKDFV5FO2kVyQ8MJDmNQ1aPX7okeDz+2hscYtME+QRYLcTAvjbpv 9kXh6n+ozhW88s9IXsbQvGfC90IOZfKvjPjGvetITrUL40zoZVoWl05hEHKDngO3M81n33 tolh/AekGDipvv+tKQuUNAnLLd1u3Sw= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-39-tf42dWcxNrajL9EWTE2-pw-1; Wed, 08 Apr 2026 20:16:32 -0400 X-MC-Unique: tf42dWcxNrajL9EWTE2-pw-1 X-Mimecast-MFC-AGG-ID: tf42dWcxNrajL9EWTE2-pw_1775693789 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-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id B2D20180044D; Thu, 9 Apr 2026 00:16:28 +0000 (UTC) Received: from GoldenWind.redhat.com (unknown [10.22.80.49]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id E99E7300019F; Thu, 9 Apr 2026 00:16:24 +0000 (UTC) From: Lyude Paul To: nouveau@lists.freedesktop.org, Gary Guo , Daniel Almeida , rust-for-linux@vger.kernel.org, Danilo Krummrich , dri-devel@lists.freedesktop.org Cc: Matthew Maurer , FUJITA Tomonori , Lorenzo Stoakes , christian.koenig@amd.com, Asahi Lina , Miguel Ojeda , Andreas Hindborg , Simona Vetter , Alice Ryhl , Boqun Feng , Sumit Semwal , Krishna Ketan Rai , linux-media@vger.kernel.org, Shankari Anand , David Airlie , Benno Lossin , Viresh Kumar , linaro-mm-sig@lists.linaro.org, Asahi Lina , Greg Kroah-Hartman , kernel@vger.kernel.org Subject: [PATCH v10 5/5] rust: drm: gem: Add vmap functions to shmem bindings Date: Wed, 8 Apr 2026 20:12:51 -0400 Message-ID: <20260409001559.622026-6-lyude@redhat.com> In-Reply-To: <20260409001559.622026-1-lyude@redhat.com> References: <20260409001559.622026-1-lyude@redhat.com> Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 X-Mimecast-MFC-PROC-ID: a1QJGW2NCIo-oeysE5Tbo9uyadCdRICWz_-mkmWo6tw_1775693789 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true One of the more obvious use cases for gem shmem objects is the ability to create mappings into their contents. So, let's hook this up in our rust bindings. 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). Signed-off-by: Lyude Paul --- V7: * Switch over to the new iosys map bindings that use the Io trait V8: * Get rid of iosys_map bindings for now, only support non-iomem types * s/as_shmem()/as_raw_shmem() V9: * Get rid of some outdated comments I missed * Add missing SIZE check to raw_vmap() * Add a proper unit test that ensures that we actually validate SIZE at compile-time. Turns out it takes only 34 lines to make a boilerplate DRM driver for a kunit test :) * Add unit tests * Add some missing #[inline]s V10: * Correct issue with iomem error path We previously called raw_vunmap() if we got an iomem allocation, but raw_vunmap() was written such that it assumed all allocations were sysmem allocations. Fix this by just making raw_vunmap() accept a iosys_map. rust/kernel/drm/gem/shmem.rs | 354 +++++++++++++++++++++++++++++++++++ 1 file changed, 354 insertions(+) diff --git a/rust/kernel/drm/gem/shmem.rs b/rust/kernel/drm/gem/shmem.rs index 111be446213df..6c186d83f528e 100644 --- a/rust/kernel/drm/gem/shmem.rs +++ b/rust/kernel/drm/gem/shmem.rs @@ -26,6 +26,11 @@ from_err_ptr, // to_result, }, + io::{ + Io, + IoCapable, + IoKnownSize, // + }, prelude::*, scatterlist, types::{ @@ -35,6 +40,11 @@ }; use core::{ cell::UnsafeCell, + ffi::c_void, + mem::{ + self, + MaybeUninit, // + }, ops::{ Deref, DerefMut, // @@ -45,6 +55,7 @@ }, }; use gem::{ + BaseObject, BaseObjectPrivate, DriverObject, IntoGEMObject, // @@ -288,6 +299,84 @@ pub fn owned_sg_table(&self, dev: &device::Device) -> Result> // `Some(Devres>)`. Ok(SGTable(self.into())) } + + /// Attempt to create a vmap from the gem object, and confirm the size of said vmap. + fn raw_vmap(&self, min_size: usize) -> Result<*mut c_void> { + if self.size() < min_size { + return Err(ENOSPC); + } + + 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(), ptr::null_mut()); + let ret = bindings::drm_gem_shmem_vmap_locked(self.as_raw_shmem(), map.as_mut_ptr()); + bindings::dma_resv_unlock(self.raw_dma_resv()); + ret + })?; + + // SAFETY: The call to drm_gem_shmem_vunmap_locked succeeded above, so we are guaranteed + // that map is properly initialized. + let map = unsafe { map.assume_init() }; + + // XXX: We don't currently support iomem allocations + if map.is_iomem { + // SAFETY: + // - The vmap operation above succeeded, guaranteeing that `map` points to a valid + // memory mapping. + // - We checked that this is an iomem allocation, making it safe to read vaddr_iomem + unsafe { self.raw_vunmap(map) }; + + Err(ENOTSUPP) + } else { + // SAFETY: We checked that this is not an iomem allocation, making it safe to read vaddr + Ok(unsafe { map.__bindgen_anon_1.vaddr }) + } + } + + /// Unmap a vmap from the gem object. + /// + /// # Safety + /// + /// - The caller promises that `map` is a valid 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, mut map: bindings::iosys_map) { + 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, ptr::null_mut()); + bindings::drm_gem_shmem_vunmap_locked(self.as_raw_shmem(), &mut map); + bindings::dma_resv_unlock(resv); + } + } + + /// Creates and returns a virtual kernel memory mapping for this object. + #[inline] + pub fn vmap(&self) -> Result> { + Ok(VMapRef { + // INVARIANT: `raw_vmap()` checks that the gem object is at least as large as `SIZE`. + addr: self.raw_vmap(SIZE)?, + owner: self, + }) + } + + /// Creates and returns an owned reference to a virtual kernel memory mapping for this object. + #[inline] + pub fn owned_vmap(&self) -> Result> { + Ok(VMap { + // INVARIANT: `raw_vmap()` checks that the gem object is at least as large as `SIZE`. + addr: self.raw_vmap(SIZE)?, + owner: self.into(), + }) + } } impl Deref for Object { @@ -386,6 +475,154 @@ unsafe impl Send for SGTableMap {} // it points to is guaranteed to be thread-safe. unsafe impl Sync for SGTableMap {} +macro_rules! impl_vmap_io_capable { + ($impl:ident, $ty:ty $(, $lifetime:lifetime )?) => { + impl<$( $lifetime ,)? D: DriverObject, const SIZE: usize> IoCapable<$ty> + for $impl<$( $lifetime ,)? D, SIZE> + { + #[inline(always)] + unsafe fn io_read(&self, address: usize) -> $ty { + let ptr = address as *mut $ty; + + // SAFETY: The safety contract of `io_read` guarantees that address is a valid + // address within the bounds of `Self` of at least the size of $ty, and is properly + // aligned. + unsafe { ptr::read(ptr) } + } + + #[inline(always)] + unsafe fn io_write(&self, value: $ty, address: usize) { + let ptr = address as *mut $ty; + + // SAFETY: The safety contract of `io_write` guarantees that address is a valid + // address within the bounds of `Self` of at least the size of $ty, and is properly + // aligned. + unsafe { ptr::write(ptr, value) } + } + } + }; +} + +// Implement various traits common to both VMap types +macro_rules! impl_vmap_common { + ($impl:ident $(, $lifetime:lifetime )?) => { + impl<$( $lifetime ,)? D, const SIZE: usize> $impl<$( $lifetime ,)? D, SIZE> + where + D: DriverObject, + { + /// Borrows a reference to the object that owns this virtual mapping. + #[inline(always)] + pub fn owner(&self) -> &Object { + &self.owner + } + } + + impl<$( $lifetime ,)? D, const SIZE: usize> Drop for $impl<$( $lifetime ,)? D, SIZE> + where + D: DriverObject, + { + #[inline(always)] + fn drop(&mut self) { + // SAFETY: + // - Our existence is proof that this map was previously created using self.owner. + // - Since we are in Drop, we are guaranteed that no one will access the memory + // through this mapping after calling this. + unsafe { + self.owner.raw_vunmap(bindings::iosys_map { + is_iomem: false, + __bindgen_anon_1: bindings::iosys_map__bindgen_ty_1 { vaddr: self.addr } + }) + }; + } + } + + impl<$( $lifetime ,)? D, const SIZE: usize> Io for $impl<$( $lifetime ,)? D, SIZE> + where + D: DriverObject, + { + #[inline(always)] + fn addr(&self) -> usize { + self.addr as usize + } + + #[inline(always)] + fn maxsize(&self) -> usize { + self.owner.size() + } + } + + impl<$( $lifetime ,)? D, const SIZE: usize> IoKnownSize for $impl<$( $lifetime ,)? D, SIZE> + where + D: DriverObject, + { + const MIN_SIZE: usize = SIZE; + } + + impl_vmap_io_capable!($impl, u8 $( , $lifetime )?); + impl_vmap_io_capable!($impl, u16 $( , $lifetime )?); + impl_vmap_io_capable!($impl, u32 $( , $lifetime )?); + #[cfg(CONFIG_64BIT)] + impl_vmap_io_capable!($impl, u64 $( , $lifetime )?); + }; +} + +/// An owned reference to a virtual mapping for a shmem-based GEM object in kernel address space. +/// +/// # Invariants +/// +/// - The size of `owner` is >= SIZE. +/// - The memory pointed to by addr remains valid at least until this object is dropped. +pub struct VMap { + addr: *mut c_void, + owner: ARef>, +} + +impl_vmap_common!(VMap); + +impl Clone for VMap { + #[inline] + 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, const SIZE: usize> From> for VMap { + #[inline] + fn from(value: VMapRef<'a, D, SIZE>) -> Self { + let this = Self { + addr: value.addr, + owner: value.owner.into(), + }; + + mem::forget(value); + this + } +} + +// SAFETY: addr is guaranteed to be valid and accessible for the lifetime of VMap, ensuring its +// safe to send across threads. +unsafe impl Send for VMap {} +// SAFETY: addr is guaranteed to be valid and accessible for the lifetime of VMap, ensuring its +// safe to send across threads. +unsafe impl Sync for VMap {} + +/// A borrowed reference to a virtual mapping for a shmem-based GEM object in kernel address space. +pub struct VMapRef<'a, D: DriverObject, const SIZE: usize = 0> { + addr: *mut c_void, + owner: &'a Object, +} + +impl_vmap_common!(VMapRef, 'a); + +impl<'a, D: DriverObject, const SIZE: usize> Clone for VMapRef<'a, D, SIZE> { + #[inline] + fn clone(&self) -> Self { + // SAFETY: We have a successful vmap already, so this can't fail + unsafe { self.owner.vmap().unwrap_unchecked() } + } +} + /// 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 @@ -413,3 +650,120 @@ fn deref(&self) -> &Self::Target { unsafe { (*self.0.sgt_res.get()).as_ref().unwrap_unchecked() } } } + +#[kunit_tests(rust_drm_gem_shmem)] +mod tests { + use super::*; + use crate::{ + drm, + faux, + page::PAGE_SIZE, // + }; + + // The bare minimum needed to create a fake drm driver for kunit + + #[pin_data] + struct KunitData {} + struct KunitDriver; + struct KunitFile; + #[pin_data] + struct KunitObject {} + + const INFO: drm::DriverInfo = drm::DriverInfo { + major: 0, + minor: 0, + patchlevel: 0, + name: c"kunit", + desc: c"Kunit", + }; + + impl drm::file::DriverFile for KunitFile { + type Driver = KunitDriver; + + fn open(_dev: &drm::Device) -> Result>> { + Ok(KBox::new(Self, GFP_KERNEL)?.into()) + } + } + + impl gem::DriverObject for KunitObject { + type Driver = KunitDriver; + type Args = (); + + fn new( + _dev: &drm::Device, + _size: usize, + _args: Self::Args, + ) -> impl PinInit { + try_pin_init!(KunitObject {}) + } + } + + #[vtable] + impl drm::Driver for KunitDriver { + type Data = KunitData; + type File = KunitFile; + type Object = Object; + + const INFO: drm::DriverInfo = INFO; + const IOCTLS: &'static [drm::ioctl::DrmIoctlDescriptor] = &[]; + } + + fn create_drm_dev() -> Result<(faux::Registration, ARef>)> { + // Create a faux DRM device so we can test gem object creation. + let data = try_pin_init!(KunitData {}); + let dev = faux::Registration::new(c"Kunit", None)?; + let drm = drm::Device::::new(dev.as_ref(), data)?; + + Ok((dev, drm)) + } + + #[test] + fn compile_time_vmap_sizes() -> Result { + let (_dev, drm) = create_drm_dev()?; + + // Create a gem object to test with + let cfg_ = ObjectConfig:: { + map_wc: false, + parent_resv_obj: None, + }; + let obj = Object::::new(&drm, PAGE_SIZE, cfg_, ())?; + + // Try creating a normal vmap + obj.vmap::()?; + + // Try creating a vmap that's smaller then the size we specified + obj.vmap::<{ PAGE_SIZE - 100 }>()?; + + // Make sure creating a vmap that's too large fails + assert!(obj.vmap::<{ PAGE_SIZE + 200 }>().is_err()); + + Ok(()) + } + + #[test] + fn vmap_io() -> Result { + let (_dev, drm) = create_drm_dev()?; + + // Create a gem object to test with + let cfg_ = ObjectConfig:: { + map_wc: false, + parent_resv_obj: None, + }; + let obj = Object::::new(&drm, PAGE_SIZE, cfg_, ())?; + + let vmap = obj.vmap::()?; + + vmap.write8(0xDE, 0x0); + assert_eq!(vmap.read8(0x0), 0xDE); + vmap.write32(0xFFFFFFFF, 0x20); + + assert_eq!(vmap.read32(0x20), 0xFFFFFFFF); + + assert_eq!(vmap.read8(0x20), 0xFF); + assert_eq!(vmap.read8(0x21), 0xFF); + assert_eq!(vmap.read8(0x22), 0xFF); + assert_eq!(vmap.read8(0x23), 0xFF); + + Ok(()) + } +} -- 2.53.0