6.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Juergen Gross jgross@suse.com
[ Upstream commit 70045cf6593cbf0740956ea9b7b4269142c6ee38 ]
When compiling the kernel with LLVM, the following warning was issued:
drivers/xen/gntdev.c:991: warning: stack frame size (1160) exceeds limit (1024) in function 'gntdev_ioctl'
The main reason is struct gntdev_copy_batch which is located on the stack and has a size of nearly 1kb.
For performance reasons it shouldn't by just dynamically allocated instead, so allocate a new instance when needed and instead of freeing it put it into a list of free structs anchored in struct gntdev_priv.
Fixes: a4cdb556cae0 ("xen/gntdev: add ioctl for grant copy") Reported-by: Abinash Singh abinashsinghlalotra@gmail.com Reviewed-by: Stefano Stabellini sstabellini@kernel.org Signed-off-by: Juergen Gross jgross@suse.com Message-ID: 20250703073259.17356-1-jgross@suse.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/xen/gntdev-common.h | 4 +++ drivers/xen/gntdev.c | 71 ++++++++++++++++++++++++++----------- 2 files changed, 54 insertions(+), 21 deletions(-)
diff --git a/drivers/xen/gntdev-common.h b/drivers/xen/gntdev-common.h index 9c286b2a1900..ac8ce3179ba2 100644 --- a/drivers/xen/gntdev-common.h +++ b/drivers/xen/gntdev-common.h @@ -26,6 +26,10 @@ struct gntdev_priv { /* lock protects maps and freeable_maps. */ struct mutex lock;
+ /* Free instances of struct gntdev_copy_batch. */ + struct gntdev_copy_batch *batch; + struct mutex batch_lock; + #ifdef CONFIG_XEN_GRANT_DMA_ALLOC /* Device for which DMA memory is allocated. */ struct device *dma_dev; diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c index 61faea1f0663..1f2160765618 100644 --- a/drivers/xen/gntdev.c +++ b/drivers/xen/gntdev.c @@ -56,6 +56,18 @@ MODULE_AUTHOR("Derek G. Murray Derek.Murray@cl.cam.ac.uk, " "Gerd Hoffmann kraxel@redhat.com"); MODULE_DESCRIPTION("User-space granted page access driver");
+#define GNTDEV_COPY_BATCH 16 + +struct gntdev_copy_batch { + struct gnttab_copy ops[GNTDEV_COPY_BATCH]; + struct page *pages[GNTDEV_COPY_BATCH]; + s16 __user *status[GNTDEV_COPY_BATCH]; + unsigned int nr_ops; + unsigned int nr_pages; + bool writeable; + struct gntdev_copy_batch *next; +}; + static unsigned int limit = 64*1024; module_param(limit, uint, 0644); MODULE_PARM_DESC(limit, @@ -584,6 +596,8 @@ static int gntdev_open(struct inode *inode, struct file *flip) INIT_LIST_HEAD(&priv->maps); mutex_init(&priv->lock);
+ mutex_init(&priv->batch_lock); + #ifdef CONFIG_XEN_GNTDEV_DMABUF priv->dmabuf_priv = gntdev_dmabuf_init(flip); if (IS_ERR(priv->dmabuf_priv)) { @@ -608,6 +622,7 @@ static int gntdev_release(struct inode *inode, struct file *flip) { struct gntdev_priv *priv = flip->private_data; struct gntdev_grant_map *map; + struct gntdev_copy_batch *batch;
pr_debug("priv %p\n", priv);
@@ -620,6 +635,14 @@ static int gntdev_release(struct inode *inode, struct file *flip) } mutex_unlock(&priv->lock);
+ mutex_lock(&priv->batch_lock); + while (priv->batch) { + batch = priv->batch; + priv->batch = batch->next; + kfree(batch); + } + mutex_unlock(&priv->batch_lock); + #ifdef CONFIG_XEN_GNTDEV_DMABUF gntdev_dmabuf_fini(priv->dmabuf_priv); #endif @@ -785,17 +808,6 @@ static long gntdev_ioctl_notify(struct gntdev_priv *priv, void __user *u) return rc; }
-#define GNTDEV_COPY_BATCH 16 - -struct gntdev_copy_batch { - struct gnttab_copy ops[GNTDEV_COPY_BATCH]; - struct page *pages[GNTDEV_COPY_BATCH]; - s16 __user *status[GNTDEV_COPY_BATCH]; - unsigned int nr_ops; - unsigned int nr_pages; - bool writeable; -}; - static int gntdev_get_page(struct gntdev_copy_batch *batch, void __user *virt, unsigned long *gfn) { @@ -953,36 +965,53 @@ static int gntdev_grant_copy_seg(struct gntdev_copy_batch *batch, static long gntdev_ioctl_grant_copy(struct gntdev_priv *priv, void __user *u) { struct ioctl_gntdev_grant_copy copy; - struct gntdev_copy_batch batch; + struct gntdev_copy_batch *batch; unsigned int i; int ret = 0;
if (copy_from_user(©, u, sizeof(copy))) return -EFAULT;
- batch.nr_ops = 0; - batch.nr_pages = 0; + mutex_lock(&priv->batch_lock); + if (!priv->batch) { + batch = kmalloc(sizeof(*batch), GFP_KERNEL); + } else { + batch = priv->batch; + priv->batch = batch->next; + } + mutex_unlock(&priv->batch_lock); + if (!batch) + return -ENOMEM; + + batch->nr_ops = 0; + batch->nr_pages = 0;
for (i = 0; i < copy.count; i++) { struct gntdev_grant_copy_segment seg;
if (copy_from_user(&seg, ©.segments[i], sizeof(seg))) { ret = -EFAULT; + gntdev_put_pages(batch); goto out; }
- ret = gntdev_grant_copy_seg(&batch, &seg, ©.segments[i].status); - if (ret < 0) + ret = gntdev_grant_copy_seg(batch, &seg, ©.segments[i].status); + if (ret < 0) { + gntdev_put_pages(batch); goto out; + }
cond_resched(); } - if (batch.nr_ops) - ret = gntdev_copy(&batch); - return ret; + if (batch->nr_ops) + ret = gntdev_copy(batch); + + out: + mutex_lock(&priv->batch_lock); + batch->next = priv->batch; + priv->batch = batch; + mutex_unlock(&priv->batch_lock);
- out: - gntdev_put_pages(&batch); return ret; }