| Message ID | 20220306021534.83553-1-jarkko@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [RFC] mm: Add f_ops->populate() | expand |
On Sun, Mar 06, 2022 at 04:15:33AM +0200, Jarkko Sakkinen wrote: > Sometimes you might want to use MAP_POPULATE to ask a device driver to > initialize the device memory in some specific manner. SGX driver can use > this to request more memory by issuing ENCLS[EAUG] x86 opcode for each > page in the address range. > > Add f_ops->populate() with the same parameters as f_ops->mmap() and make > it conditionally called inside call_mmap(). Update call sites > accodingly. Your device driver has a ->mmap operation. Why does it need another one? More explanation required here.
On Sun, Mar 06, 2022 at 02:57:55AM +0000, Matthew Wilcox wrote: > On Sun, Mar 06, 2022 at 04:15:33AM +0200, Jarkko Sakkinen wrote: > > Sometimes you might want to use MAP_POPULATE to ask a device driver to > > initialize the device memory in some specific manner. SGX driver can use > > this to request more memory by issuing ENCLS[EAUG] x86 opcode for each > > page in the address range. > > > > Add f_ops->populate() with the same parameters as f_ops->mmap() and make > > it conditionally called inside call_mmap(). Update call sites > > accodingly. > > Your device driver has a ->mmap operation. Why does it need another > one? More explanation required here. f_ops->mmap() would require an additional parameter, which results heavy refactoring. struct file_operations has 1125 references in the kernel tree, so I decided to check this way around first. BR, Jarkko
On Sun, Mar 06, 2022 at 05:21:11AM +0200, Jarkko Sakkinen wrote: > On Sun, Mar 06, 2022 at 02:57:55AM +0000, Matthew Wilcox wrote: > > On Sun, Mar 06, 2022 at 04:15:33AM +0200, Jarkko Sakkinen wrote: > > > Sometimes you might want to use MAP_POPULATE to ask a device driver to > > > initialize the device memory in some specific manner. SGX driver can use > > > this to request more memory by issuing ENCLS[EAUG] x86 opcode for each > > > page in the address range. > > > > > > Add f_ops->populate() with the same parameters as f_ops->mmap() and make > > > it conditionally called inside call_mmap(). Update call sites > > > accodingly. > > > > Your device driver has a ->mmap operation. Why does it need another > > one? More explanation required here. > > f_ops->mmap() would require an additional parameter, which results > heavy refactoring. > > struct file_operations has 1125 references in the kernel tree, so I > decided to check this way around first. Are you saying that your device driver behaves differently if MAP_POPULATE is set versus if it isn't? That seems hideously broken.
On Sun, Mar 06, 2022 at 03:52:12AM +0000, Matthew Wilcox wrote: > On Sun, Mar 06, 2022 at 05:21:11AM +0200, Jarkko Sakkinen wrote: > > On Sun, Mar 06, 2022 at 02:57:55AM +0000, Matthew Wilcox wrote: > > > On Sun, Mar 06, 2022 at 04:15:33AM +0200, Jarkko Sakkinen wrote: > > > > Sometimes you might want to use MAP_POPULATE to ask a device driver to > > > > initialize the device memory in some specific manner. SGX driver can use > > > > this to request more memory by issuing ENCLS[EAUG] x86 opcode for each > > > > page in the address range. > > > > > > > > Add f_ops->populate() with the same parameters as f_ops->mmap() and make > > > > it conditionally called inside call_mmap(). Update call sites > > > > accodingly. > > > > > > Your device driver has a ->mmap operation. Why does it need another > > > one? More explanation required here. > > > > f_ops->mmap() would require an additional parameter, which results > > heavy refactoring. > > > > struct file_operations has 1125 references in the kernel tree, so I > > decided to check this way around first. > > Are you saying that your device driver behaves differently if > MAP_POPULATE is set versus if it isn't? That seems hideously broken. MAP_POPULATE does not do anything (according to __mm_populate in mm/gup.c) with VMA's that have some sort of device/IO memory, i.e. vm_flags intersecting with VM_PFNMAP | VM_IO. I can extend the guard obviously to: if (!ret && do_populate && file->f_op->populate && !!(vma->vm_flags & (VM_IO | VM_PFNMAP))) file->f_op->populate(file, vma); BR, Jarkko
On Sun, Mar 06, 2022 at 06:11:21AM +0200, Jarkko Sakkinen wrote: > On Sun, Mar 06, 2022 at 03:52:12AM +0000, Matthew Wilcox wrote: > > On Sun, Mar 06, 2022 at 05:21:11AM +0200, Jarkko Sakkinen wrote: > > > On Sun, Mar 06, 2022 at 02:57:55AM +0000, Matthew Wilcox wrote: > > > > On Sun, Mar 06, 2022 at 04:15:33AM +0200, Jarkko Sakkinen wrote: > > > > > Sometimes you might want to use MAP_POPULATE to ask a device driver to > > > > > initialize the device memory in some specific manner. SGX driver can use > > > > > this to request more memory by issuing ENCLS[EAUG] x86 opcode for each > > > > > page in the address range. > > > > > > > > > > Add f_ops->populate() with the same parameters as f_ops->mmap() and make > > > > > it conditionally called inside call_mmap(). Update call sites > > > > > accodingly. > > > > > > > > Your device driver has a ->mmap operation. Why does it need another > > > > one? More explanation required here. > > > > > > f_ops->mmap() would require an additional parameter, which results > > > heavy refactoring. > > > > > > struct file_operations has 1125 references in the kernel tree, so I > > > decided to check this way around first. > > > > Are you saying that your device driver behaves differently if > > MAP_POPULATE is set versus if it isn't? That seems hideously broken. > > MAP_POPULATE does not do anything (according to __mm_populate in mm/gup.c) > with VMA's that have some sort of device/IO memory, i.e. vm_flags > intersecting with VM_PFNMAP | VM_IO. > > I can extend the guard obviously to: > > if (!ret && do_populate && file->f_op->populate && > !!(vma->vm_flags & (VM_IO | VM_PFNMAP))) > file->f_op->populate(file, vma); Are you deliberately avoiding the question? I'm not asking about implementation. I'm asking about the semantics of MAP_POPULATE with your driver.
On Sun, Mar 06, 2022 at 04:19:26AM +0000, Matthew Wilcox wrote: > On Sun, Mar 06, 2022 at 06:11:21AM +0200, Jarkko Sakkinen wrote: > > On Sun, Mar 06, 2022 at 03:52:12AM +0000, Matthew Wilcox wrote: > > > On Sun, Mar 06, 2022 at 05:21:11AM +0200, Jarkko Sakkinen wrote: > > > > On Sun, Mar 06, 2022 at 02:57:55AM +0000, Matthew Wilcox wrote: > > > > > On Sun, Mar 06, 2022 at 04:15:33AM +0200, Jarkko Sakkinen wrote: > > > > > > Sometimes you might want to use MAP_POPULATE to ask a device driver to > > > > > > initialize the device memory in some specific manner. SGX driver can use > > > > > > this to request more memory by issuing ENCLS[EAUG] x86 opcode for each > > > > > > page in the address range. > > > > > > > > > > > > Add f_ops->populate() with the same parameters as f_ops->mmap() and make > > > > > > it conditionally called inside call_mmap(). Update call sites > > > > > > accodingly. > > > > > > > > > > Your device driver has a ->mmap operation. Why does it need another > > > > > one? More explanation required here. > > > > > > > > f_ops->mmap() would require an additional parameter, which results > > > > heavy refactoring. > > > > > > > > struct file_operations has 1125 references in the kernel tree, so I > > > > decided to check this way around first. > > > > > > Are you saying that your device driver behaves differently if > > > MAP_POPULATE is set versus if it isn't? That seems hideously broken. > > > > MAP_POPULATE does not do anything (according to __mm_populate in mm/gup.c) > > with VMA's that have some sort of device/IO memory, i.e. vm_flags > > intersecting with VM_PFNMAP | VM_IO. > > > > I can extend the guard obviously to: > > > > if (!ret && do_populate && file->f_op->populate && > > !!(vma->vm_flags & (VM_IO | VM_PFNMAP))) > > file->f_op->populate(file, vma); > > Are you deliberately avoiding the question? I'm not asking about > implementation. I'm asking about the semantics of MAP_POPULATE with > your driver. No. I just noticed a bug in the guard from your comment that I wanted point out. With the next version I post the corresponding change to the driver, in order to see this in context. BR, Jarkko
On Sun, Mar 06, 2022 at 06:25:52AM +0200, Jarkko Sakkinen wrote: > > Are you deliberately avoiding the question? I'm not asking about > > implementation. I'm asking about the semantics of MAP_POPULATE with > > your driver. > > No. I just noticed a bug in the guard from your comment that I wanted > point out. > > With the next version I post the corresponding change to the driver, > in order to see this in context. Oh, good grief. Don't bother. NAK.
diff --git a/arch/mips/kernel/vdso.c b/arch/mips/kernel/vdso.c index 3d0cf471f2fe..89f3f3da9abd 100644 --- a/arch/mips/kernel/vdso.c +++ b/arch/mips/kernel/vdso.c @@ -102,7 +102,7 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) base = mmap_region(NULL, STACK_TOP, PAGE_SIZE, VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC, - 0, NULL); + 0, NULL, false); if (IS_ERR_VALUE(base)) { ret = base; goto out; diff --git a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c index 1b526039a60d..4c71f64d6a79 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c @@ -107,7 +107,7 @@ static int i915_gem_dmabuf_mmap(struct dma_buf *dma_buf, struct vm_area_struct * if (!obj->base.filp) return -ENODEV; - ret = call_mmap(obj->base.filp, vma); + ret = call_mmap(obj->base.filp, vma, false); if (ret) return ret; diff --git a/fs/coda/file.c b/fs/coda/file.c index 29dd87be2fb8..e14f312fdbf8 100644 --- a/fs/coda/file.c +++ b/fs/coda/file.c @@ -173,7 +173,7 @@ coda_file_mmap(struct file *coda_file, struct vm_area_struct *vma) spin_unlock(&cii->c_lock); vma->vm_file = get_file(host_file); - ret = call_mmap(vma->vm_file, vma); + ret = call_mmap(vma->vm_file, vma, false); if (ret) { /* if call_mmap fails, our caller will put host_file so we diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c index fa125feed0ff..b963a9397e80 100644 --- a/fs/overlayfs/file.c +++ b/fs/overlayfs/file.c @@ -503,7 +503,7 @@ static int ovl_mmap(struct file *file, struct vm_area_struct *vma) vma_set_file(vma, realfile); old_cred = ovl_override_creds(file_inode(file)->i_sb); - ret = call_mmap(vma->vm_file, vma); + ret = call_mmap(vma->vm_file, vma, false); revert_creds(old_cred); ovl_file_accessed(file); diff --git a/include/linux/fs.h b/include/linux/fs.h index e2d892b201b0..fb90284e1c82 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1993,6 +1993,7 @@ struct file_operations { long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long); long (*compat_ioctl) (struct file *, unsigned int, unsigned long); int (*mmap) (struct file *, struct vm_area_struct *); + int (*populate)(struct file *, struct vm_area_struct *); unsigned long mmap_supported_flags; int (*open) (struct inode *, struct file *); int (*flush) (struct file *, fl_owner_t id); @@ -2074,9 +2075,14 @@ static inline ssize_t call_write_iter(struct file *file, struct kiocb *kio, return file->f_op->write_iter(kio, iter); } -static inline int call_mmap(struct file *file, struct vm_area_struct *vma) +static inline int call_mmap(struct file *file, struct vm_area_struct *vma, bool do_populate) { - return file->f_op->mmap(file, vma); + int ret = file->f_op->mmap(file, vma); + + if (!ret && do_populate) + ret = file->f_op->populate(file, vma); + + return ret; } extern ssize_t vfs_read(struct file *, char __user *, size_t, loff_t *); diff --git a/include/linux/mm.h b/include/linux/mm.h index 213cc569b192..6c8c036f423b 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2683,7 +2683,7 @@ extern unsigned long get_unmapped_area(struct file *, unsigned long, unsigned lo extern unsigned long mmap_region(struct file *file, unsigned long addr, unsigned long len, vm_flags_t vm_flags, unsigned long pgoff, - struct list_head *uf); + struct list_head *uf, bool do_populate); extern unsigned long do_mmap(struct file *file, unsigned long addr, unsigned long len, unsigned long prot, unsigned long flags, unsigned long pgoff, unsigned long *populate, struct list_head *uf); diff --git a/ipc/shm.c b/ipc/shm.c index b3048ebd5c31..89b28f32acf0 100644 --- a/ipc/shm.c +++ b/ipc/shm.c @@ -587,7 +587,7 @@ static int shm_mmap(struct file *file, struct vm_area_struct *vma) if (ret) return ret; - ret = call_mmap(sfd->file, vma); + ret = call_mmap(sfd->file, vma, do_populate); if (ret) { shm_close(vma); return ret; diff --git a/mm/mmap.c b/mm/mmap.c index 1e8fdb0b51ed..5eca79957d4c 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1413,6 +1413,7 @@ unsigned long do_mmap(struct file *file, unsigned long addr, unsigned long flags, unsigned long pgoff, unsigned long *populate, struct list_head *uf) { + bool do_populate = (flags & (MAP_POPULATE | MAP_NONBLOCK)) == MAP_POPULATE; struct mm_struct *mm = current->mm; vm_flags_t vm_flags; int pkey = 0; @@ -1579,10 +1580,9 @@ unsigned long do_mmap(struct file *file, unsigned long addr, vm_flags |= VM_NORESERVE; } - addr = mmap_region(file, addr, len, vm_flags, pgoff, uf); + addr = mmap_region(file, addr, len, vm_flags, pgoff, uf, do_populate); if (!IS_ERR_VALUE(addr) && - ((vm_flags & VM_LOCKED) || - (flags & (MAP_POPULATE | MAP_NONBLOCK)) == MAP_POPULATE)) + ((vm_flags & VM_LOCKED) || do_populate)) *populate = len; return addr; } @@ -1721,7 +1721,7 @@ static inline int accountable_mapping(struct file *file, vm_flags_t vm_flags) unsigned long mmap_region(struct file *file, unsigned long addr, unsigned long len, vm_flags_t vm_flags, unsigned long pgoff, - struct list_head *uf) + struct list_head *uf, bool do_populate) { struct mm_struct *mm = current->mm; struct vm_area_struct *vma, *prev, *merge; @@ -1790,7 +1790,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr, } vma->vm_file = get_file(file); - error = call_mmap(file, vma); + error = call_mmap(file, vma, do_populate); if (error) goto unmap_and_free_vma; diff --git a/mm/nommu.c b/mm/nommu.c index 55a9e48a7a02..a3c20b803c27 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -941,7 +941,7 @@ static int do_mmap_shared_file(struct vm_area_struct *vma) { int ret; - ret = call_mmap(vma->vm_file, vma); + ret = call_mmap(vma->vm_file, vma, false); if (ret == 0) { vma->vm_region->vm_top = vma->vm_region->vm_end; return 0; @@ -972,7 +972,7 @@ static int do_mmap_private(struct vm_area_struct *vma, * - VM_MAYSHARE will be set if it may attempt to share */ if (capabilities & NOMMU_MAP_DIRECT) { - ret = call_mmap(vma->vm_file, vma); + ret = call_mmap(vma->vm_file, vma, false); if (ret == 0) { /* shouldn't return success if we're not sharing */ BUG_ON(!(vma->vm_flags & VM_MAYSHARE));
Sometimes you might want to use MAP_POPULATE to ask a device driver to initialize the device memory in some specific manner. SGX driver can use this to request more memory by issuing ENCLS[EAUG] x86 opcode for each page in the address range. Add f_ops->populate() with the same parameters as f_ops->mmap() and make it conditionally called inside call_mmap(). Update call sites accodingly. Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org> --- arch/mips/kernel/vdso.c | 2 +- drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c | 2 +- fs/coda/file.c | 2 +- fs/overlayfs/file.c | 2 +- include/linux/fs.h | 10 ++++++++-- include/linux/mm.h | 2 +- ipc/shm.c | 2 +- mm/mmap.c | 10 +++++----- mm/nommu.c | 4 ++-- 9 files changed, 21 insertions(+), 15 deletions(-)