diff mbox series

[RFC] mm: Add f_ops->populate()

Message ID 20220306021534.83553-1-jarkko@kernel.org (mailing list archive)
State New, archived
Headers show
Series [RFC] mm: Add f_ops->populate() | expand

Commit Message

Jarkko Sakkinen March 6, 2022, 2:15 a.m. UTC
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(-)

Comments

Matthew Wilcox March 6, 2022, 2:57 a.m. UTC | #1
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.
Jarkko Sakkinen March 6, 2022, 3:21 a.m. UTC | #2
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
Matthew Wilcox March 6, 2022, 3:52 a.m. UTC | #3
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.
Jarkko Sakkinen March 6, 2022, 4:11 a.m. UTC | #4
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
Matthew Wilcox March 6, 2022, 4:19 a.m. UTC | #5
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.
Jarkko Sakkinen March 6, 2022, 4:25 a.m. UTC | #6
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
Matthew Wilcox March 6, 2022, 4:36 a.m. UTC | #7
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 mbox series

Patch

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));