On Fri, 16 Dec 2022 at 10:39, Sumit Garg <sumit.garg@xxxxxxxxxx> wrote: > > On Fri, 16 Dec 2022 at 06:11, Ira Weiny <ira.weiny@xxxxxxxxx> wrote: > > > > On Fri, Oct 07, 2022 at 10:12:57AM +0200, Jens Wiklander wrote: > > > On Thu, Oct 6, 2022 at 8:20 PM Linus Torvalds > > > <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > > > > > > > > On Wed, Oct 5, 2022 at 11:24 PM Sumit Garg <sumit.garg@xxxxxxxxxx> wrote: > > > > > > > > > > Sorry but you need to get your driver mainline in order to support > > > > > vmalloc interface. > > > > > > > > Actually, I think even then we shouldn't support vmalloc - and > > > > register_shm_helper() just needs to be changed to pass in an array of > > > > actual page pointers instead. > > > > > > register_shm_helper() is an internal function, I suppose it's what's > > > passed to tee_shm_register_user_buf() and especially > > > tee_shm_register_kernel_buf() in this case. > > > > > > So the gain is that in the kernel it becomes the caller's > > > responsibility to provide the array of page pointers and the TEE > > > subsystem doesn't need to care about what kind of kernel memory it is > > > any longer. Yes, that should avoid eventual complexities with > > > vmalloc() etc. > > > > I finally spent some time digging into this again. > > > > Overall I'm not opposed to trying to clean up the code more but I feel like the > > removal of TEE_SHM_USER_MAPPED is too complex for the main goal; to remove a > > caller of kmap_to_page(). > > > > Not only is that flag used in release_registered_pages() but it is also used in > > tee_shm_fop_mmap(). I'm not following exactly why. I think this is to allow > > mmap of the tee_shm's allocated by kernel users? > > No, its rather to allow mmap of tee_shm allocated via > tee_shm_alloc_user_buf(). Have a look at its user-space usage here > [1]. So overall I agree here that we can't get rid of > TEE_SHM_USER_MAPPED completely as it has a valid mmap use-case. > > [1] https://github.com/OP-TEE/optee_client/blob/master/libteec/src/tee_client_api.c#L907 > > > Which I _think_ is > > orthogonal to the callers of tee_shm_register_kernel_buf()? > > > > > > > > > > > > > At that point TEE_SHM_USER_MAPPED should also go away, because then > > > > it's the caller that should just do either the user space page > > > > pinning, or pass in the kernel page pointer. > > > > > > > > JensW, is there some reason that wouldn't work? > > > > > > We still need to know if it's kernel or user pages in > > > release_registered_pages(). > > > > Yes. > > > > As I dug into this it seemed ok to define a tee_shm_kernel_free(). Pull out > > the allocation of the page array from register_shm_helper() such that it could > > be handled by tee_shm_register_kernel_buf() and this new tee_shm_kernel_free(). > > > > +1 > > > This seems reasonable because the only callers of tee_shm_register_kernel_buf() > > are in trusted_tee.c and they all call tee_shm_free() on the registered memory > > prior to returning. > > > > Other callers[*] of tee_shm_free() obtained tee_shm from > > tee_shm_alloc_kernel_buf() which AFAICT avoids all this nonsense. > > > > [*] such as .../drivers/firmware/broadcom/tee_bnxt_fw.c. > > > > > > > > The struct tee_shm:s acquired with syscalls from user space are > > > reference counted. As are the kernel tee_shm:s, but I believe we could > > > separate them to avoid reference counting tee_shm:s used by kernel > > > clients if needed. I'll need to look closer at this if we're going to > > > use that approach. > > > > > > Without reference counting the caller of tee_shm_free() can be certain > > > that the secure world is done with the memory so we could delegate the > > > kernel pages part of release_registered_pages() to the caller instead. > > > > > > > I'm not sure I follow you here. Would this be along the lines of creating a > > tee_shm_free_kernel() to be used in trusted_tee.c for those specific kernel > > data? > > I can't find a reason/use-case for the TEE subsystem to keep a > refcount of memory registered by other kernel drivers like > trusted_tee.c. So yes I think it should be safe to directly free that > shm via tee_shm_free_kernel(). Also with that we can simplify shm > registration by kernel clients via directly passing page pointers to > tee_shm_register_kernel_buf() (I would rather rename this API as > tee_shm_register_kernel_pages()). Okay, so I will take up this work and get rid of kmap_to_page invocation from the TEE subsystem. Ira, You can then rebase your patchset over my work. -Sumit > > > > > Overall I feel like submitting this series again with Christoph and Al's > > comments addressed is the best way forward to get rid of kmap_to_page(). I > > would really like to get moving on that to avoid any further issues with the > > kmap conversions. > > > > But if folks feel strongly enough about removing that flag I can certainly try > > to do so. > > > > Ira > > > > > Cheers, > > > Jens > > > > > > > > > > > Linus
