Linaro-mm-sig

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Re: [Linaro-mm-sig] [PATCH v3 1/2] habanalabs: define uAPI to export FD for DMA-BUF

by Christian König

Am 22.06.21 um 17:40 schrieb Oded Gabbay: > On Tue, Jun 22, 2021 at 6:31 PM Christian König > <christian.koenig(a)amd.com> wrote: >> >> >> Am 22.06.21 um 17:28 schrieb Jason Gunthorpe: >>> On Tue, Jun 22, 2021 at 05:24:08PM +0200, Christian König wrote: >>> >>>>>> I will take two GAUDI devices and use one as an exporter and one as an >>>>>> importer. I want to see that the solution works end-to-end, with real >>>>>> device DMA from importer to exporter. >>>>> I can tell you it doesn't. Stuffing physical addresses directly into >>>>> the sg list doesn't involve any of the IOMMU code so any configuration >>>>> that requires IOMMU page table setup will not work. >>>> Sure it does. See amdgpu_vram_mgr_alloc_sgt: >>>> >>>> amdgpu_res_first(res, offset, length, &cursor); >>> ^^^^^^^^^^ >>> >>> I'm not talking about the AMD driver, I'm talking about this patch. >>> >>> + bar_address = hdev->dram_pci_bar_start + >>> + (pages[cur_page] - prop->dram_base_address); >>> + sg_dma_address(sg) = bar_address; >> Yeah, that is indeed not working. >> >> Oded you need to use dma_map_resource() for this. >> >> Christian. > Yes, of course. > But will it be enough ? > Jason said that supporting IOMMU isn't nice when we don't have struct pages. > I fail to understand the connection, I need to dig into this. Question is what you want to do with this? A struct page is always needed if you want to do stuff like HMM with it, if you only want P2P between device I actually recommend to avoid it. Christian. > > Oded > >> >> >>> Jason

5 years, 1 month

Re: [Linaro-mm-sig] [PATCH v3 1/2] habanalabs: define uAPI to export FD for DMA-BUF

by Jason Gunthorpe

On Tue, Jun 22, 2021 at 06:24:28PM +0300, Oded Gabbay wrote: > On Tue, Jun 22, 2021 at 6:11 PM Jason Gunthorpe <jgg(a)ziepe.ca> wrote: > > > > On Tue, Jun 22, 2021 at 04:12:26PM +0300, Oded Gabbay wrote: > > > > > > 1) Setting sg_page to NULL > > > > 2) 'mapping' pages for P2P DMA without going through the iommu > > > > 3) Allowing P2P DMA without using the p2p dma API to validate that it > > > > can work at all in the first place. > > > > > > > > All of these result in functional bugs in certain system > > > > configurations. > > > > > > > > Jason > > > > > > Hi Jason, > > > Thanks for the feedback. > > > Regarding point 1, why is that a problem if we disable the option to > > > mmap the dma-buf from user-space ? > > > > Userspace has nothing to do with needing struct pages or not > > > > Point 1 and 2 mostly go together, you supporting the iommu is not nice > > if you dont have struct pages. > > > > You should study Logan's patches I pointed you at as they are solving > > exactly this problem. > Yes, I do need to study them. I agree with you here. It appears I > have a hole in my understanding. I'm missing the connection between > iommu support (which I must have of course) and struct pages. Chistian explained what the AMD driver is doing by calling dma_map_resource(). Which is a hacky and slow way of achieving what Logan's series is doing. > > No, the design of the dmabuf requires the exporter to do the dma maps > > and so it is only the exporter that is wrong to omit all the iommu and > > p2p logic. > > > > RDMA is OK today only because nobody has implemented dma buf support > > in rxe/si - mainly because the only implementations of exporters don't > > Can you please educate me, what is rxe/si ? Sorry, rxe/siw - these are the all-software implementations of RDMA and they require the struct page to do a SW memory copy. They can't implement dmabuf without it. > ok... > so how come that patch-set was merged into 5.12 if it's buggy ? We only implemented true dma devices for RDMA DMABUF support, so it is isn't buggy right now. > Yes, that's what I expect to see. But I want to see it with my own > eyes and then figure out how to solve this. It might be tricky to test because you have to ensure the iommu is turned on and has a non-idenity page table. Basically if it doesn't trigger a IOMMU failure then the IOMMU isn't setup properly. Jason

5 years, 1 month

Re: [Linaro-mm-sig] [PATCH v3 1/2] habanalabs: define uAPI to export FD for DMA-BUF

by Jason Gunthorpe

On Tue, Jun 22, 2021 at 04:12:26PM +0300, Oded Gabbay wrote: > > 1) Setting sg_page to NULL > > 2) 'mapping' pages for P2P DMA without going through the iommu > > 3) Allowing P2P DMA without using the p2p dma API to validate that it > > can work at all in the first place. > > > > All of these result in functional bugs in certain system > > configurations. > > > > Jason > > Hi Jason, > Thanks for the feedback. > Regarding point 1, why is that a problem if we disable the option to > mmap the dma-buf from user-space ? Userspace has nothing to do with needing struct pages or not Point 1 and 2 mostly go together, you supporting the iommu is not nice if you dont have struct pages. You should study Logan's patches I pointed you at as they are solving exactly this problem. > In addition, I didn't see any problem with sg_page being NULL in the > RDMA p2p dma-buf code. Did I miss something here ? No, the design of the dmabuf requires the exporter to do the dma maps and so it is only the exporter that is wrong to omit all the iommu and p2p logic. RDMA is OK today only because nobody has implemented dma buf support in rxe/si - mainly because the only implementations of exporters don't set the struct page and are thus buggy. > I will take two GAUDI devices and use one as an exporter and one as an > importer. I want to see that the solution works end-to-end, with real > device DMA from importer to exporter. I can tell you it doesn't. Stuffing physical addresses directly into the sg list doesn't involve any of the IOMMU code so any configuration that requires IOMMU page table setup will not work. Jason

5 years, 1 month

Re: [Linaro-mm-sig] [PATCH v3 1/2] habanalabs: define uAPI to export FD for DMA-BUF

by Jason Gunthorpe

On Tue, Jun 22, 2021 at 03:04:30PM +0300, Oded Gabbay wrote: > On Tue, Jun 22, 2021 at 3:01 PM Jason Gunthorpe <jgg(a)ziepe.ca> wrote: > > > > On Tue, Jun 22, 2021 at 11:42:27AM +0300, Oded Gabbay wrote: > > > On Tue, Jun 22, 2021 at 9:37 AM Christian König > > > <ckoenig.leichtzumerken(a)gmail.com> wrote: > > > > > > > > Am 22.06.21 um 01:29 schrieb Jason Gunthorpe: > > > > > On Mon, Jun 21, 2021 at 10:24:16PM +0300, Oded Gabbay wrote: > > > > > > > > > >> Another thing I want to emphasize is that we are doing p2p only > > > > >> through the export/import of the FD. We do *not* allow the user to > > > > >> mmap the dma-buf as we do not support direct IO. So there is no access > > > > >> to these pages through the userspace. > > > > > Arguably mmaping the memory is a better choice, and is the direction > > > > > that Logan's series goes in. Here the use of DMABUF was specifically > > > > > designed to allow hitless revokation of the memory, which this isn't > > > > > even using. > > > > > > > > The major problem with this approach is that DMA-buf is also used for > > > > memory which isn't CPU accessible. > > > > That isn't an issue here because the memory is only intended to be > > used with P2P transfers so it must be CPU accessible. > > > > > > That was one of the reasons we didn't even considered using the mapping > > > > memory approach for GPUs. > > > > Well, now we have DEVICE_PRIVATE memory that can meet this need > > too.. Just nobody has wired it up to hmm_range_fault() > > > > > > > So you are taking the hit of very limited hardware support and reduced > > > > > performance just to squeeze into DMABUF.. > > > > > > Thanks Jason for the clarification, but I honestly prefer to use > > > DMA-BUF at the moment. > > > It gives us just what we need (even more than what we need as you > > > pointed out), it is *already* integrated and tested in the RDMA > > > subsystem, and I'm feeling comfortable using it as I'm somewhat > > > familiar with it from my AMD days. > > > > You still have the issue that this patch is doing all of this P2P > > stuff wrong - following the already NAK'd AMD approach. > > Could you please point me exactly to the lines of code that are wrong > in your opinion ? 1) Setting sg_page to NULL 2) 'mapping' pages for P2P DMA without going through the iommu 3) Allowing P2P DMA without using the p2p dma API to validate that it can work at all in the first place. All of these result in functional bugs in certain system configurations. Jason

5 years, 1 month

Re: [Linaro-mm-sig] [PATCH v3 1/2] habanalabs: define uAPI to export FD for DMA-BUF

by Jason Gunthorpe

On Mon, Jun 21, 2021 at 10:24:16PM +0300, Oded Gabbay wrote: > Another thing I want to emphasize is that we are doing p2p only > through the export/import of the FD. We do *not* allow the user to > mmap the dma-buf as we do not support direct IO. So there is no access > to these pages through the userspace. Arguably mmaping the memory is a better choice, and is the direction that Logan's series goes in. Here the use of DMABUF was specifically designed to allow hitless revokation of the memory, which this isn't even using. So you are taking the hit of very limited hardware support and reduced performance just to squeeze into DMABUF.. Jason

5 years, 1 month

Re: [Linaro-mm-sig] [PATCH v3 1/2] habanalabs: define uAPI to export FD for DMA-BUF

by Jason Gunthorpe

On Mon, Jun 21, 2021 at 07:26:14PM +0300, Oded Gabbay wrote: > On Mon, Jun 21, 2021 at 5:12 PM Jason Gunthorpe <jgg(a)ziepe.ca> wrote: > > > > On Mon, Jun 21, 2021 at 03:02:10PM +0200, Greg KH wrote: > > > On Mon, Jun 21, 2021 at 02:28:48PM +0200, Daniel Vetter wrote: > > > > > > Also I'm wondering which is the other driver that we share buffers > > > > with. The gaudi stuff doesn't have real struct pages as backing > > > > storage, it only fills out the dma_addr_t. That tends to blow up with > > > > other drivers, and the only place where this is guaranteed to work is > > > > if you have a dynamic importer which sets the allow_peer2peer flag. > > > > Adding maintainers from other subsystems who might want to chime in > > > > here. So even aside of the big question as-is this is broken. > > > > > > From what I can tell this driver is sending the buffers to other > > > instances of the same hardware, > > > > A dmabuf is consumed by something else in the kernel calling > > dma_buf_map_attachment() on the FD. > > > > What is the other side of this? I don't see any > > dma_buf_map_attachment() calls in drivers/misc, or added in this patch > > set. > > This patch-set is only to enable the support for the exporter side. > The "other side" is any generic RDMA networking device that will want > to perform p2p communication over PCIe with our GAUDI accelerator. > An example is indeed the mlnx5 card which has already integrated > support for being an "importer". It raises the question of how you are testing this if you aren't using it with the only intree driver: mlx5. Jason

5 years, 1 month

Re: [Linaro-mm-sig] [PATCH v3 1/2] habanalabs: define uAPI to export FD for DMA-BUF

by Daniel Vetter

On Fri, Jun 18, 2021 at 2:36 PM Oded Gabbay <ogabbay(a)kernel.org> wrote: > User process might want to share the device memory with another > driver/device, and to allow it to access it over PCIe (P2P). > > To enable this, we utilize the dma-buf mechanism and add a dma-buf > exporter support, so the other driver can import the device memory and > access it. > > The device memory is allocated using our existing allocation uAPI, > where the user will get a handle that represents the allocation. > > The user will then need to call the new > uAPI (HL_MEM_OP_EXPORT_DMABUF_FD) and give the handle as a parameter. > > The driver will return a FD that represents the DMA-BUF object that > was created to match that allocation. > > Signed-off-by: Oded Gabbay <ogabbay(a)kernel.org> > Reviewed-by: Tomer Tayar <ttayar(a)habana.ai> Mission acomplished, we've gone full circle, and the totally-not-a-gpu driver is now trying to use gpu infrastructure. And seems to have gained vram meanwhile too. Next up is going to be synchronization using dma_fence so you can pass buffers back&forth without stalls among drivers. Bonus points for this being at v3 before it shows up on dri-devel and cc's dma-buf folks properly (not quite all, I added the missing people). I think we roughly have two options here a) Greg continues to piss off dri-devel folks while trying to look cute&cuddly and steadfastly claiming that this accelator doesn't work like any of the other accelerator drivers we have in drivers/gpu/drm. All while the driver ever more looks like one of these other accel drivers. b) We finally do what we should have done years back and treat this as a proper driver submission and review it on dri-devel instead of sneaking it in through other channels because the merge criteria dri-devel has are too onerous and people who don't have experience with accel stacks for the past 20 years or so don't like them. "But this probably means a new driver and big disruption!" Not my problem, I'm not the dude who has to come up with an excuse for this because I didn't merge the driver in the first place. I do get to throw a "we all told you so" in though, but that's not helping. Also I'm wondering which is the other driver that we share buffers with. The gaudi stuff doesn't have real struct pages as backing storage, it only fills out the dma_addr_t. That tends to blow up with other drivers, and the only place where this is guaranteed to work is if you have a dynamic importer which sets the allow_peer2peer flag. Adding maintainers from other subsystems who might want to chime in here. So even aside of the big question as-is this is broken. Currently only 2 drivers set allow_peer2peer, so those are the only ones who can consume these buffers from device memory. Pinging those folks specifically. Doug/Jason from infiniband: Should we add linux-rdma to the dma-buf wildcard match so that you can catch these next time around too? At least when people use scripts/get_maintainers.pl correctly. All the other subsystems using dma-buf are on there already (dri-devel, linux-media and linaro-mm-sig for android/arm embedded stuff). Cheers, Daniel > --- > include/uapi/misc/habanalabs.h | 28 +++++++++++++++++++++++++++- > 1 file changed, 27 insertions(+), 1 deletion(-) > > diff --git a/include/uapi/misc/habanalabs.h b/include/uapi/misc/habanalabs.h > index a47a731e4527..aa3d8e0ba060 100644 > --- a/include/uapi/misc/habanalabs.h > +++ b/include/uapi/misc/habanalabs.h > @@ -808,6 +808,10 @@ union hl_wait_cs_args { > #define HL_MEM_OP_UNMAP 3 > /* Opcode to map a hw block */ > #define HL_MEM_OP_MAP_BLOCK 4 > +/* Opcode to create DMA-BUF object for an existing device memory allocation > + * and to export an FD of that DMA-BUF back to the caller > + */ > +#define HL_MEM_OP_EXPORT_DMABUF_FD 5 > > /* Memory flags */ > #define HL_MEM_CONTIGUOUS 0x1 > @@ -878,11 +882,26 @@ struct hl_mem_in { > /* Virtual address returned from HL_MEM_OP_MAP */ > __u64 device_virt_addr; > } unmap; > + > + /* HL_MEM_OP_EXPORT_DMABUF_FD */ > + struct { > + /* Handle returned from HL_MEM_OP_ALLOC. In Gaudi, > + * where we don't have MMU for the device memory, the > + * driver expects a physical address (instead of > + * a handle) in the device memory space. > + */ > + __u64 handle; > + /* Size of memory allocation. Relevant only for GAUDI */ > + __u64 mem_size; > + } export_dmabuf_fd; > }; > > /* HL_MEM_OP_* */ > __u32 op; > - /* HL_MEM_* flags */ > + /* HL_MEM_* flags. > + * For the HL_MEM_OP_EXPORT_DMABUF_FD opcode, this field holds the > + * DMA-BUF file/FD flags. > + */ > __u32 flags; > /* Context ID - Currently not in use */ > __u32 ctx_id; > @@ -919,6 +938,13 @@ struct hl_mem_out { > > __u32 pad; > }; > + > + /* Returned in HL_MEM_OP_EXPORT_DMABUF_FD. Represents the > + * DMA-BUF object that was created to describe a memory > + * allocation on the device's memory space. The FD should be > + * passed to the importer driver > + */ > + __u64 fd; > }; > }; > > -- > 2.25.1 > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch

5 years, 1 month

Re: [Linaro-mm-sig] [PATCH v3 2/2] drm: protect drm_master pointers in drm_lease.c

by Daniel Vetter

On Sun, Jun 20, 2021 at 07:03:27PM +0800, Desmond Cheong Zhi Xi wrote: > Currently, direct copies of drm_file->master pointers should be > protected by drm_device.master_mutex when being dereferenced. This is > because drm_file->master is not invariant for the lifetime of > drm_file. If drm_file is not the creator of master, then > drm_file->is_master is false, and a call to drm_setmaster_ioctl will > invoke drm_new_set_master, which then allocates a new master for > drm_file and puts the old master. > > Thus, without holding drm_device.master_mutex, the old value of > drm_file->master could be freed while it is being used by another > concurrent process. > > In drm_lease.c, there are multiple instances where drm_file->master is > accessed and dereferenced while drm_device.master_mutex is not > held. This makes drm_lease.c vulnerable to use-after-free bugs. > > We address this issue as follows: > > 1. Clarify in the kerneldoc that drm_file->master is protected by > drm_device.master_mutex. > > 2. Add a new drm_file_get_master() function that calls drm_master_get > on drm_file->master while holding on to drm_device.master_mutex. Since > drm_master_get increments the reference count of master, this > prevents master from being freed until we unreference it with > drm_master_put. > > 3. In each case where drm_file->master is directly accessed and > eventually dereferenced in drm_lease.c, we wrap the access in a call > to the new drm_file_get_master function, then unreference the master > pointer once we are done using it. > > Reported-by: Daniel Vetter <daniel.vetter(a)ffwll.ch> > Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx(a)gmail.com> I think this approach looks much clearer than the previous. I've found a few smaller things below still. I think at least ... Cheers, Daniel > --- > drivers/gpu/drm/drm_auth.c | 22 ++++++++++++++ > drivers/gpu/drm/drm_lease.c | 57 ++++++++++++++++++++++++++----------- > include/drm/drm_auth.h | 1 + > include/drm/drm_file.h | 15 ++++++++-- > 4 files changed, 75 insertions(+), 20 deletions(-) > > diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c > index 86d4b72e95cb..0c64a77c67a6 100644 > --- a/drivers/gpu/drm/drm_auth.c > +++ b/drivers/gpu/drm/drm_auth.c > @@ -384,6 +384,28 @@ struct drm_master *drm_master_get(struct drm_master *master) > } > EXPORT_SYMBOL(drm_master_get); > > +/** > + * drm_file_get_master - reference @file_priv->master > + * @file_priv: DRM file private > + * > + * Increments the reference count of @file_priv->master and returns Does this format correctly? I'd go with "&drm_file.master of @file_priv". > + * @file_priv->master. > + * > + * Master pointers returned from this function should be unreferenced using > + * drm_master_put(). > + */ > +struct drm_master *drm_file_get_master(struct drm_file *file_priv) > +{ > + struct drm_master *master; > + > + mutex_lock(&file_priv->master->dev->master_mutex); > + master = drm_master_get(file_priv->master); > + mutex_unlock(&file_priv->master->dev->master_mutex); > + > + return master; > +} > +EXPORT_SYMBOL(drm_file_get_master); > + > static void drm_master_destroy(struct kref *kref) > { > struct drm_master *master = container_of(kref, struct drm_master, refcount); > diff --git a/drivers/gpu/drm/drm_lease.c b/drivers/gpu/drm/drm_lease.c > index da4f085fc09e..65eab82f8acc 100644 > --- a/drivers/gpu/drm/drm_lease.c > +++ b/drivers/gpu/drm/drm_lease.c > @@ -107,10 +107,17 @@ static bool _drm_has_leased(struct drm_master *master, int id) > */ > bool _drm_lease_held(struct drm_file *file_priv, int id) > { > + bool ret; > + struct drm_master *master; > + > if (!file_priv || !file_priv->master) So here we still have a ->master access outside of the locked code section. I think the best fix for that would be to move the NULL check into drm_file_get_master (where we grab the lock already anyway), and update the kerneldoc to state that it might return NULL. Same with all the checks for ->master below. > return true; > > - return _drm_lease_held_master(file_priv->master, id); > + master = drm_file_get_master(file_priv); > + ret = _drm_lease_held_master(master, id); > + drm_master_put(&master); > + > + return ret; > } > > /** > @@ -132,10 +139,11 @@ bool drm_lease_held(struct drm_file *file_priv, int id) > if (!file_priv || !file_priv->master || !file_priv->master->lessor) > return true; master->lessor dereferenced outside the lock or without holding a reference. > > - master = file_priv->master; > + master = drm_file_get_master(file_priv); > mutex_lock(&master->dev->mode_config.idr_mutex); > ret = _drm_lease_held_master(master, id); > mutex_unlock(&master->dev->mode_config.idr_mutex); > + drm_master_put(&master); > return ret; > } > > @@ -158,7 +166,7 @@ uint32_t drm_lease_filter_crtcs(struct drm_file *file_priv, uint32_t crtcs_in) > if (!file_priv || !file_priv->master || !file_priv->master->lessor) > return crtcs_in; Same here. > > - master = file_priv->master; > + master = drm_file_get_master(file_priv); > dev = master->dev; > > count_in = count_out = 0; > @@ -177,6 +185,7 @@ uint32_t drm_lease_filter_crtcs(struct drm_file *file_priv, uint32_t crtcs_in) > count_in++; > } > mutex_unlock(&master->dev->mode_config.idr_mutex); > + drm_master_put(&master); > return crtcs_out; > } > > @@ -490,7 +499,7 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, > size_t object_count; > int ret = 0; > struct idr leases; > - struct drm_master *lessor = lessor_priv->master; > + struct drm_master *lessor; > struct drm_master *lessee = NULL; > struct file *lessee_file = NULL; > struct file *lessor_file = lessor_priv->filp; > @@ -502,12 +511,6 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, > if (!drm_core_check_feature(dev, DRIVER_MODESET)) > return -EOPNOTSUPP; > > - /* Do not allow sub-leases */ > - if (lessor->lessor) { > - DRM_DEBUG_LEASE("recursive leasing not allowed\n"); > - return -EINVAL; > - } > - > /* need some objects */ > if (cl->object_count == 0) { > DRM_DEBUG_LEASE("no objects in lease\n"); > @@ -519,12 +522,22 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, > return -EINVAL; > } > > + lessor = drm_file_get_master(lessor_priv); > + /* Do not allow sub-leases */ > + if (lessor->lessor) { Here we check after grabbing the reference, so looks correct. > + DRM_DEBUG_LEASE("recursive leasing not allowed\n"); > + ret = -EINVAL; > + goto out_lessor; > + } > + > object_count = cl->object_count; > > object_ids = memdup_user(u64_to_user_ptr(cl->object_ids), > array_size(object_count, sizeof(__u32))); > - if (IS_ERR(object_ids)) > - return PTR_ERR(object_ids); > + if (IS_ERR(object_ids)) { > + ret = PTR_ERR(object_ids); > + goto out_lessor; > + } > > idr_init(&leases); > > @@ -535,14 +548,15 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, > if (ret) { > DRM_DEBUG_LEASE("lease object lookup failed: %i\n", ret); > idr_destroy(&leases); > - return ret; > + goto out_lessor; > } > > /* Allocate a file descriptor for the lease */ > fd = get_unused_fd_flags(cl->flags & (O_CLOEXEC | O_NONBLOCK)); > if (fd < 0) { > idr_destroy(&leases); > - return fd; > + ret = fd; > + goto out_lessor; > } > > DRM_DEBUG_LEASE("Creating lease\n"); > @@ -578,6 +592,7 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, > /* Hook up the fd */ > fd_install(fd, lessee_file); > > + drm_master_put(&lessor); > DRM_DEBUG_LEASE("drm_mode_create_lease_ioctl succeeded\n"); > return 0; > > @@ -587,6 +602,8 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, > out_leases: > put_unused_fd(fd); > > +out_lessor: > + drm_master_put(&lessor); > DRM_DEBUG_LEASE("drm_mode_create_lease_ioctl failed: %d\n", ret); > return ret; > } > @@ -609,7 +626,7 @@ int drm_mode_list_lessees_ioctl(struct drm_device *dev, > struct drm_mode_list_lessees *arg = data; > __u32 __user *lessee_ids = (__u32 __user *) (uintptr_t) (arg->lessees_ptr); > __u32 count_lessees = arg->count_lessees; > - struct drm_master *lessor = lessor_priv->master, *lessee; > + struct drm_master *lessor, *lessee; > int count; > int ret = 0; > > @@ -620,6 +637,7 @@ int drm_mode_list_lessees_ioctl(struct drm_device *dev, > if (!drm_core_check_feature(dev, DRIVER_MODESET)) > return -EOPNOTSUPP; > > + lessor = drm_file_get_master(lessor_priv); > DRM_DEBUG_LEASE("List lessees for %d\n", lessor->lessee_id); > > mutex_lock(&dev->mode_config.idr_mutex); > @@ -643,6 +661,7 @@ int drm_mode_list_lessees_ioctl(struct drm_device *dev, > arg->count_lessees = count; > > mutex_unlock(&dev->mode_config.idr_mutex); > + drm_master_put(&lessor); > > return ret; > } > @@ -662,7 +681,7 @@ int drm_mode_get_lease_ioctl(struct drm_device *dev, > struct drm_mode_get_lease *arg = data; > __u32 __user *object_ids = (__u32 __user *) (uintptr_t) (arg->objects_ptr); > __u32 count_objects = arg->count_objects; > - struct drm_master *lessee = lessee_priv->master; > + struct drm_master *lessee; > struct idr *object_idr; > int count; > void *entry; > @@ -676,6 +695,7 @@ int drm_mode_get_lease_ioctl(struct drm_device *dev, > if (!drm_core_check_feature(dev, DRIVER_MODESET)) > return -EOPNOTSUPP; > > + lessee = drm_file_get_master(lessee_priv); > DRM_DEBUG_LEASE("get lease for %d\n", lessee->lessee_id); > > mutex_lock(&dev->mode_config.idr_mutex); > @@ -703,6 +723,7 @@ int drm_mode_get_lease_ioctl(struct drm_device *dev, > arg->count_objects = count; > > mutex_unlock(&dev->mode_config.idr_mutex); > + drm_master_put(&lessee); > > return ret; > } > @@ -721,7 +742,7 @@ int drm_mode_revoke_lease_ioctl(struct drm_device *dev, > void *data, struct drm_file *lessor_priv) > { > struct drm_mode_revoke_lease *arg = data; > - struct drm_master *lessor = lessor_priv->master; > + struct drm_master *lessor; > struct drm_master *lessee; > int ret = 0; > > @@ -731,6 +752,7 @@ int drm_mode_revoke_lease_ioctl(struct drm_device *dev, > if (!drm_core_check_feature(dev, DRIVER_MODESET)) > return -EOPNOTSUPP; > > + lessor = drm_file_get_master(lessor_priv); > mutex_lock(&dev->mode_config.idr_mutex); > > lessee = _drm_find_lessee(lessor, arg->lessee_id); > @@ -751,6 +773,7 @@ int drm_mode_revoke_lease_ioctl(struct drm_device *dev, > > fail: > mutex_unlock(&dev->mode_config.idr_mutex); > + drm_master_put(&lessor); > > return ret; > } > diff --git a/include/drm/drm_auth.h b/include/drm/drm_auth.h > index 6bf8b2b78991..f99d3417f304 100644 > --- a/include/drm/drm_auth.h > +++ b/include/drm/drm_auth.h > @@ -107,6 +107,7 @@ struct drm_master { > }; > > struct drm_master *drm_master_get(struct drm_master *master); > +struct drm_master *drm_file_get_master(struct drm_file *file_priv); > void drm_master_put(struct drm_master **master); > bool drm_is_current_master(struct drm_file *fpriv); > > diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h > index b81b3bfb08c8..e9931fca4ab7 100644 > --- a/include/drm/drm_file.h > +++ b/include/drm/drm_file.h > @@ -226,9 +226,18 @@ struct drm_file { > /** > * @master: > * > - * Master this node is currently associated with. Only relevant if > - * drm_is_primary_client() returns true. Note that this only > - * matches &drm_device.master if the master is the currently active one. > + * Master this node is currently associated with. Protected by struct > + * &drm_device.master_mutex. > + * > + * Only relevant if drm_is_primary_client() returns true. Note that > + * this only matches &drm_device.master if the master is the currently > + * active one. > + * > + * When obtaining a copy of this pointer, it is recommended to either > + * hold struct &drm_device.master_mutex for the duration of the > + * pointer's use, or to use drm_file_get_master() if struct > + * &drm_device.master_mutex is not currently held and there is no other > + * need to hold it. This prevents @master from being freed during use. > * > * See also @authentication and @is_master and the :ref:`section on > * primary nodes and authentication <drm_primary_node>`. > -- > 2.25.1 > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch

5 years, 1 month

Fixing problems around shared fences and RCU in DMA-buf

by Christian König

Hi everyone and especially Daniel, this is the revised patch set to fix and rework dma_buf_poll(). The new code should avoid problems with RCU and also now correctly waits for all fences in the resv object. The rest of the series is then the well known change to dma_resv_test_signaled(), nouveau and now new also msm. Then last are two patches which drop the workarounds from amdgpu, but those can wait till the next cycle. I think it would be rather good if the have at least to change to dma_buf_poll() pushed in this merge window and maybe even CC stable since this looks really broken to me. Please review, test and/or comment. Thanks, Christian.

5 years, 1 month

Introduce fence iterators to abstract dma_resv RCU handling

by Christian König

Hi guys, during the recent discussion about SLAB_TYPESAFE_BY_RCU, dma_fence_get_rcu and dma_fence_get_rcu_safe we found that the RCU handling for dma_resv objects was implemented multiple times. Unfortunately a lot of those implementations get the rather complicated dance with RCU and the sequence number handling wrong. So this patch set aims to audit and unify this by providing an iterator which automatically restarts when a modification to the dma_resv object is detected. The result is pretty impressive I think since this not only mean that we got rid of all those incorrect dma_fence_get_rcu() cases, but also reduce the overall loc count quite a bit. Please review and/or comment. Cheers, Christian.

5 years, 1 month

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