[PATCH RFC v2 27/50] samples/kvm: Remove mem_provider_ops from sample provider
From: Ackerley Tng via B4 Relay
Date: Thu Oct 22 2026 - 19:35:29 EST
From: Ackerley Tng <ackerleytng@xxxxxxxxxx>
Trim this memory provider down to just the memory provider parts first,
removing mem_provider_ops and related callbacks.
Leave the integration with guest_memfd alternative providers to future
patches.
Signed-off-by: Ackerley Tng <ackerleytng@xxxxxxxxxx>
---
samples/Kconfig | 4 +-
samples/kvm/mem_provider_sample.c | 121 ++++----------------------------------
samples/kvm/mem_provider_sample.h | 8 +--
3 files changed, 18 insertions(+), 115 deletions(-)
diff --git a/samples/Kconfig b/samples/Kconfig
index a06eafb5d7ba4..29a0efe49ac3a 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -328,9 +328,9 @@ source "samples/damon/Kconfig"
config SAMPLE_KVM_MEM_PROVIDER
tristate "Build sample memory provider -- loadable module only"
- depends on MEM_PROVIDER && CONTIG_ALLOC && X86_64 && m
+ depends on CONTIG_ALLOC && X86_64 && m
help
- This builds a sample memory provider (include/linux/mem_provider.h).
+ This builds a sample memory provider.
Its files can back a guest_memfd and be mapped by iommufd.
It allocates a contiguous region with alloc_contig_pages()
and carves out child provider files on the fly.
diff --git a/samples/kvm/mem_provider_sample.c b/samples/kvm/mem_provider_sample.c
index 574c712a11389..294b2d65fc29d 100644
--- a/samples/kvm/mem_provider_sample.c
+++ b/samples/kvm/mem_provider_sample.c
@@ -2,13 +2,10 @@
/*
* mem_provider_sample - a sample memory provider.
*
- * The module owns a region of physical memory and lends it through provider
- * files (include/linux/mem_provider.h). A VMM passes the same file to
- * KVM_CREATE_GUEST_MEMFD, for the guest, and to IOMMU_IOAS_MAP_FILE, for the
- * guest's devices. The module calls neither KVM nor iommufd: it answers
- * "what is page N" and revokes a range when the answer changes.
+ * The module owns a region of physical memory and lends it through child
+ * files.
*
- * The control device /dev/mem_provider_sample creates provider files.
+ * The control device /dev/mem_provider_sample creates child files.
* NEW_CHILD carves part of the region into a child file. A page can also
* be taken away. See mem_provider_sample.h.
*
@@ -21,7 +18,6 @@
#include <linux/fs.h>
#include <linux/gfp.h>
#include <linux/io.h>
-#include <linux/mem_provider.h>
#include <linux/miscdevice.h>
#include <linux/mm.h>
#include <linux/module.h>
@@ -31,14 +27,11 @@
#include "mem_provider_sample.h"
/*
- * One provider file.
+ * One child file.
*
- * Lock order: mps_root.lock, then mps_info.lock, then the consumers' locks
- * (taken by their revoke callbacks). get_page() takes no lock, so a
- * consumer can call it from its fault paths and its revoke callback.
+ * Lock order: mps_root.lock, then mps_info.lock.
*/
struct mps_info {
- struct mem_provider_file mpf;
struct mutex lock; /* the bitmaps */
unsigned long base_pfn;
@@ -69,89 +62,7 @@ static struct mps_root {
struct list_head children;
} mps_root;
-/* Does @info have page @index now? Called with or without info->lock. */
-static bool mps_page_present(struct mps_info *info, unsigned long index)
-{
- return !test_bit(index, info->absent);
-}
-
-/*
- * The length of the run from @index of pages with the same state as @index:
- * present.
- */
-static unsigned long mps_run(struct mps_info *info, unsigned long index)
-{
- unsigned long end = info->npages;
-
- end = min(end, find_next_bit(info->absent, info->npages, index + 1));
- return end - index;
-}
-
-/* ---- Provider operations ------------------------------------------------ */
-
-static struct mem_provider_file *
-mps_mp_attach(struct file *file, loff_t size)
-{
- struct mps_info *info = file->private_data;
-
- if (size > (loff_t)info->npages << PAGE_SHIFT)
- return ERR_PTR(-EINVAL);
- return &info->mpf;
-}
-
-static void mps_mp_detach(struct mem_provider_file *mpf)
-{
-}
-
-/*
- * Reads the bitmaps without info->lock. A change runs under the lock and
- * revokes the range afterwards, so an answer that a change makes out of date
- * is dropped by the consumer.
- */
-static int mps_mp_get_page(struct mem_provider_file *mpf, pgoff_t index,
- unsigned long *pfn, int *max_order, u32 *attrs)
-{
- struct mps_info *info = container_of(mpf, struct mps_info, mpf);
- unsigned long run;
-
- if (index >= info->npages)
- return -EINVAL;
-
- if (!mps_page_present(info, index))
- return -EFAULT;
-
- /* The aligned block around @index must be one run. */
- run = mps_run(info, index);
- while (*max_order) {
- unsigned long first = ALIGN_DOWN(index, 1UL << *max_order);
-
- if (first + (1UL << *max_order) <= index + run &&
- (first == index || mps_page_present(info, first)) &&
- mps_run(info, first) >= 1UL << *max_order)
- break;
- (*max_order)--;
- }
-
- *pfn = info->base_pfn + index;
- return 0;
-}
-
-static const struct mem_provider_ops mps_mp_ops = {
- .attach = mps_mp_attach,
- .detach = mps_mp_detach,
- .get_page = mps_mp_get_page,
-};
-
-/* Tell the consumers that pages [start, end) of @info changed. */
-static void mps_revoke(struct mps_info *info, unsigned long start,
- unsigned long end)
-{
- if (end > start)
- mem_provider_revoke(&info->mpf, (loff_t)start << PAGE_SHIFT,
- (loff_t)(end - start) << PAGE_SHIFT);
-}
-
-/* ---- Provider file ------------------------------------------------------ */
+/* ---- Child file --------------------------------------------------------- */
/* Byte range [offset, offset + len) of @info as page indices. */
static int mps_range(struct mps_info *info, u64 offset, u64 len,
@@ -174,7 +85,6 @@ static void mps_set_present(struct mps_info *info, unsigned long start,
bitmap_clear(info->absent, start, end - start);
else
bitmap_set(info->absent, start, end - start);
- mps_revoke(info, start, end);
mutex_unlock(&info->lock);
}
@@ -226,15 +136,11 @@ static int mps_file_release(struct inode *inode, struct file *file)
return 0;
}
-static const struct mem_provider_fops mps_file_fops = {
- .fops = {
- .owner = THIS_MODULE,
- .fop_flags = FOP_MEM_PROVIDER,
- .release = mps_file_release,
- .unlocked_ioctl = mps_file_ioctl,
- .compat_ioctl = compat_ptr_ioctl,
- },
- .ops = &mps_mp_ops,
+static const struct file_operations mps_file_fops = {
+ .owner = THIS_MODULE,
+ .release = mps_file_release,
+ .unlocked_ioctl = mps_file_ioctl,
+ .compat_ioctl = compat_ptr_ioctl,
};
/*
@@ -253,7 +159,6 @@ static int mps_new_file(unsigned long base_pfn, unsigned long npages,
info = kzalloc_obj(*info);
if (!info)
return -ENOMEM;
- mem_provider_file_init(&info->mpf);
info->base_pfn = base_pfn;
info->npages = npages;
info->absent = bitmap_zalloc(npages, GFP_KERNEL);
@@ -269,7 +174,7 @@ static int mps_new_file(unsigned long base_pfn, unsigned long npages,
ret = fd;
goto err_free;
}
- file = anon_inode_getfile("[mem-provider-sample]", &mps_file_fops.fops,
+ file = anon_inode_getfile("[mem-provider-sample]", &mps_file_fops,
info, O_RDWR);
if (IS_ERR(file)) {
put_unused_fd(fd);
@@ -354,7 +259,7 @@ static struct file *mps_get_child(int fd, struct mps_info **infop)
if (!file)
return ERR_PTR(-EBADF);
- if (file->f_op != &mps_file_fops.fops ||
+ if (file->f_op != &mps_file_fops ||
!((struct mps_info *)file->private_data)->is_child) {
fput(file);
return ERR_PTR(-EINVAL);
diff --git a/samples/kvm/mem_provider_sample.h b/samples/kvm/mem_provider_sample.h
index 51eaf39acbad1..b520b49e56f60 100644
--- a/samples/kvm/mem_provider_sample.h
+++ b/samples/kvm/mem_provider_sample.h
@@ -6,12 +6,10 @@
#include <linux/types.h>
/*
- * A sample memory provider (include/linux/mem_provider.h).
+ * A sample memory provider.
*
- * Every fd that this module returns is a provider file. Pass it as
- * resource_fd to KVM_CREATE_GUEST_MEMFD with GUEST_MEMFD_FLAG_USE_RESOURCE,
- * and as fd to IOMMU_IOAS_MAP_FILE. Both consumers follow every change that
- * the ioctls below make.
+ * Every fd that this module returns is a child file. Pass it to
+ * KVM_CREATE_GUEST_MEMFD.
*/
#define MPS_IOCTL_BASE 'P'
--
2.56.0.257.gf7497c7d27-goog