Re: [PATCH v4 2/3] drm/panthor: Add vm_bind region with kbo range overlap check

["Adrián Larumbe" <adrian.larumbe@collabora.com>]

On 2026-07-09 09:25:13+01:00, Steven Price wrote:
> On 04/07/2026 05:46, 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 storing the end of the user VA range at VM creation time and
> > doing a quick check in the vm_bind ioctl path was the simplest workaround.
> > 
> > Fixes: tag and reference the relevant sparse binding support commit.
> > Fixes: 647810ec2476 ("drm/panthor: Add the MMU/VM logical block")
> > Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
> > Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
> > ---
> >  drivers/gpu/drm/panthor/panthor_mmu.c | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
> > index 163231c1703d..662a2c13b467 100644
> > --- a/drivers/gpu/drm/panthor/panthor_mmu.c
> > +++ b/drivers/gpu/drm/panthor/panthor_mmu.c
> > @@ -310,6 +310,9 @@ struct panthor_vm {
> >  		u64 end;
> >  	} kernel_auto_va;
> >  
> > +	/** @user_va_range: Upper boundary of VAs VM users can map objects against. */
> > +	u64 user_va_range;
> > +
> >  	/** @as: Address space related fields. */
> >  	struct {
> >  		/**
> > @@ -2893,6 +2896,8 @@ panthor_vm_create(struct panthor_device *ptdev, bool for_mcu,
> >  		va_range = full_va_range;
> >  	}
> >  
> > +	vm->user_va_range = kernel_va_start;
> > +
> >  	mutex_init(&vm->mm_lock);
> >  	drm_mm_init(&vm->mm, kernel_va_start, kernel_va_size);
> >  	vm->kernel_auto_va.start = auto_kernel_va_start;
> > @@ -2985,6 +2990,10 @@ panthor_vm_bind_prepare_op_ctx(struct drm_file *file,
> >  	if (check_add_overflow(op->va, op->size, &end))
> >  		return -EINVAL;
> >  
> > +	/* We don't allow mappings that overlap with kbo's reserved range */
> > +	if (end > vm->user_va_range)
> > +		return -EINVAL;
> > +
> 
> Squashing this with the previous patch we can do this in one check:
> 
> 	if (range_overflows(op->va, op->size, vm->user_va_range))
> 		return -EINVAL;
> 
> Thanks,
> Steve

Will do so for the next revision.