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charset="utf-8" Content-Transfer-Encoding: 8bit Subject: Re: [PATCH 1/2] drm/panthor: Add vm_bind region with kbo range intersection check From: =?utf-8?q?Adri=C3=A1n_Larumbe?= To: Boris Brezillon Cc: =?utf-8?q?Adri=C3=A1n_Larumbe?= , Steven Price , Liviu Dudau , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org In-Reply-To: <20260617205003.07e4275e@fedora-2.home> References: <20260616-vm_bind_checks-v1-0-956198602ae3@collabora.com> <20260616-vm_bind_checks-v1-1-956198602ae3@collabora.com> <20260617205003.07e4275e@fedora-2.home> Date: Fri, 19 Jun 2026 03:16:37 +0100 Message-Id: <178183539797.1716788.5917731920154470392.b4-reply@b4> X-Mailer: b4 0.15.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=4263; i=adrian.larumbe@collabora.com; h=from:subject:message-id; bh=3+ClM2jCUCrkcPwoT3pFFiLSM/LI7EC4s99PQ+OBgeQ=; b=owEB7QES/pANAwAKAQ4mfkzuU0M9AcsmYgBqNKaTJhyUXYUrEkRV9WCQ0qL43wokPrg2zlkAe vDoYKGDY0+JAbMEAAEKAB0WIQQyQDDowAUXXfk3B6QOJn5M7lNDPQUCajSmkwAKCRAOJn5M7lND PWuwC/9uksJnDrt3A0fSBBHfnoe0lqJr+uUUwk0L5QtponPy0dbtBafskeezwkMgk5JbCQWa4y/ yahCRyJRgR7a+QmhhSejsI0N2olk8cBqz8wDbRAsmt/b0KrD/HIKtfvonCbcML1MDascDmEG1bZ W9EZaFm2PiKWCWlskjkvRkEmTBx/oN2GCZFevIOIK8AYDpJZnKnNmSi9AQNnWZN/aVj+JcZ2/FB 4A/bqtBpzjBa08JnY4OoZswERWqIJ/A9lSf0p6/4r6MIBOz5vcBBVIhaIttcdLy9Ovjz/nqDIIT O6kahMuAXz+V4sC+MvXXn7tLc0TAhDzZvN51ON5IYw2UlTwhmm35unNFh0kkzpdhJgJ5A3VU1ih 5dkNRX5CFMvLHUA9ZsgOHgiYxkHyoGgx3mSajUK6HQ8d34l+vTDVWMSr0go3daE/PrLfA5urVkI qhDXpwasTQu14svK4XIMpSo6o6YE74GvMtw/f/lvEVQWMREaPuIKQfJhrr9fThWJcKTOA= X-Developer-Key: i=adrian.larumbe@collabora.com; a=openpgp; fpr=324030E8C005175DF93707A40E267E4CEE53433D On 2026-06-17 20:50:03+02:00, Boris Brezillon wrote: > On Tue, 16 Jun 2026 15:46:43 +0100 > Adrián Larumbe wrote: > > > When a VM is created, caller has to specify the range of the address space > > carve-out set aside for mapping kernel BO's. That means vm_bind mappings of > > UM-exposed BO's should not intersect with that region, but at the moment > > we're not checking this. > > > > At first, I thought of giving these values to drm_gpuvm_init() through its > > reserve_{offset, range} arguments, but it turns out that is meant for VM > > address spans that are not managed through the usual drm_gpuvm split/merge > > circuit, so I had no choice but to sort of duplicate that functionality in > > Panthor. That means we also need to keep that interval recorded in the VM. > > > > Signed-off-by: Adrián Larumbe > > --- > > drivers/gpu/drm/panthor/panthor_mmu.c | 33 +++++++++++++++++++++++++++++++++ > > 1 file changed, 33 insertions(+) > > > > diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c > > index 31cc57029c12..5625f3d34031 100644 > > --- a/drivers/gpu/drm/panthor/panthor_mmu.c > > +++ b/drivers/gpu/drm/panthor/panthor_mmu.c > > @@ -301,6 +301,15 @@ struct panthor_vm { > > /** @mm_lock: Lock protecting the @mm field. */ > > struct mutex mm_lock; > > > > + /** @kernel_va: VA-range reserved for kernel BOs. */ > > + struct { > > + /** @kernel_va.start: Start of the VA-range for kernel BOs. */ > > + u64 start; > > + > > + /** @kernel_va.range: Size of the automatic VA-range for kernel BOs. */ > > + u64 range; > > + } kernel_va; > > We can do with a single user_va_end. > > > + > > /** @kernel_auto_va: Automatic VA-range for kernel BOs. */ > > struct { > > /** @kernel_auto_va.start: Start of the automatic VA-range for kernel BOs. */ > > @@ -1309,6 +1318,24 @@ static int panthor_vm_op_ctx_prealloc_pts(struct panthor_vm_op_ctx *op_ctx) > > return 0; > > } > > > > +static bool > > +panthor_vm_is_kernel_address(struct panthor_vm *vm, > > + const struct drm_panthor_vm_bind_op *op) > > Rather than checking if the VA is not in the kernel range, I'd check > that the VA is in the user range, since that's what we want to enforce, > and if we ever decide to carve out extra sections above the user-range > that the UMD is not supposed to access, we would still catch invalid > map/unmap ops. > > > +{ > > + u32 op_type = op->flags & DRM_PANTHOR_VM_BIND_OP_TYPE_MASK; > > + u64 end, kstart, krange, kend; > > + > > + if (op_type == DRM_PANTHOR_VM_BIND_OP_TYPE_SYNC_ONLY) > > + return false; > > IIRC, we force op->va and op->size to be zero in that case[1], so no > need for this extra check IMHO. > > > + > > + end = op->va + op->size; > > + kstart = vm->kernel_va.start; > > + krange = vm->kernel_va.range; > > + kend = kstart + krange; > > + > > + return krange && op->va < kend && kstart < end; > > A single > > op->va + op->size <= vm->user_va_end; > > would do, at which point I'm not too sure adding a helper makes sense. I'll do this for v2. > > +} > > + > > #define PANTHOR_VM_BIND_OP_MAP_FLAGS \ > > (DRM_PANTHOR_VM_BIND_OP_MAP_READONLY | \ > > DRM_PANTHOR_VM_BIND_OP_MAP_NOEXEC | \ > > @@ -2891,6 +2918,8 @@ panthor_vm_create(struct panthor_device *ptdev, bool for_mcu, > > } else { > > min_va = 0; > > va_range = full_va_range; > > + vm->kernel_va.start = kernel_va_start; > > + vm->kernel_va.range = kernel_va_size; > > } > > > > mutex_init(&vm->mm_lock); > > @@ -2981,6 +3010,10 @@ panthor_vm_bind_prepare_op_ctx(struct drm_file *file, > > if (!IS_ALIGNED(op->va | op->size | op->bo_offset, vm_pgsz)) > > return -EINVAL; > > > > + /* We don't allow mappings that intersect with kbo's reserved range */ > > + if (panthor_vm_is_kernel_address(vm, op)) > > + return -EINVAL; > > + > > switch (op->flags & DRM_PANTHOR_VM_BIND_OP_TYPE_MASK) { > > case DRM_PANTHOR_VM_BIND_OP_TYPE_MAP: > > if (!(op->flags & DRM_PANTHOR_VM_BIND_OP_MAP_SPARSE)) { > > [1]https://elixir.bootlin.com/linux/v7.0.11/source/include/uapi/drm/panthor_drm.h#L588