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? 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(). 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? 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
