If VIRTIO_F_SHM_PAGE_SIZE has been negotiated and cfg_type is
VIRTIO_PCI_CAP_SHARED_MEMORY_CFG, the driver must read the page_shift
field, derive the supported page size from it, and honor it when
requesting the map of memory into the shared memory region to the
device.
Extend virtio_pci_cap to hold that field, and use it to feed
virtio_shm_region with the corresponding page size.
Signed-off-by: Sergio Lopez <slp@xxxxxxxxxx>
---
drivers/virtio/virtio_pci_modern.c | 22 +++++++++++++++++-----
include/uapi/linux/virtio_pci.h | 3 ++-
2 files changed, 19 insertions(+), 6 deletions(-)
diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
index ab0e1d9148057c431676bfacfe5f68cc97eebb12..562a8e1c2bfe6876cffabe26f02cd61ad7fea2cd 100644
--- a/drivers/virtio/virtio_pci_modern.c
+++ b/drivers/virtio/virtio_pci_modern.c
@@ -770,14 +770,15 @@ static void del_vq(struct virtio_pci_vq_info *info)
vring_del_virtqueue(vq);
}
-static int virtio_pci_find_shm_cap(struct pci_dev *dev, u8 required_id,
- u8 *bar, u64 *offset, u64 *len)
+static int virtio_pci_find_shm_cap(struct virtio_device *vdev, struct pci_dev *dev,
+ u8 required_id, u8 *bar, u64 *offset, u64 *len,
+ u32 *page_size)
{
int pos;
for (pos = pci_find_capability(dev, PCI_CAP_ID_VNDR); pos > 0;
pos = pci_find_next_capability(dev, pos, PCI_CAP_ID_VNDR)) {
- u8 type, cap_len, id, res_bar;
+ u8 type, cap_len, id, res_bar, page_shift = 0;
u32 tmp32;
u64 res_offset, res_length;
@@ -808,6 +809,15 @@ static int virtio_pci_find_shm_cap(struct pci_dev *dev, u8 required_id,
* Looks good.
*/
+ /* Read the page shift if supported. The page_shift variable is
+ * initialized to zero above, so if this feature isn't supported it
+ * will result in a page_size of 4096, a default safe value.
+ */
+ if (__virtio_test_bit(vdev, VIRTIO_F_SHM_PAGE_SIZE)) {
+ pci_read_config_byte(dev, pos + offsetof(struct virtio_pci_cap,
+ page_shift), &page_shift);
+ }
+
/* Read the lower 32bit of length and offset */
pci_read_config_dword(dev, pos + offsetof(struct virtio_pci_cap,
offset), &tmp32);
@@ -829,6 +839,7 @@ static int virtio_pci_find_shm_cap(struct pci_dev *dev, u8 required_id,
*bar = res_bar;
*offset = res_offset;
*len = res_length;
+ *page_size = 1 << (page_shift + 12);
return pos;
}
@@ -841,11 +852,12 @@ static bool vp_get_shm_region(struct virtio_device *vdev,
struct virtio_pci_device *vp_dev = to_vp_device(vdev);
struct pci_dev *pci_dev = vp_dev->pci_dev;
u8 bar;
+ u32 page_size;
u64 offset, len;
phys_addr_t phys_addr;
size_t bar_len;
- if (!virtio_pci_find_shm_cap(pci_dev, id, &bar, &offset, &len))
+ if (!virtio_pci_find_shm_cap(vdev, pci_dev, id, &bar, &offset, &len, &page_size))
return false;
phys_addr = pci_resource_start(pci_dev, bar);
@@ -865,7 +877,7 @@ static bool vp_get_shm_region(struct virtio_device *vdev,
region->len = len;
region->addr = (u64) phys_addr + offset;
- region->page_size = 4096;
+ region->page_size = page_size;
return true;
}
diff --git a/include/uapi/linux/virtio_pci.h b/include/uapi/linux/virtio_pci.h
index 8549d4571257142ac6c9dad5c01369923791a85a..1a76df52b4eccf548df78a8ee7d3a04591f55522 100644
--- a/include/uapi/linux/virtio_pci.h
+++ b/include/uapi/linux/virtio_pci.h
@@ -127,7 +127,8 @@ struct virtio_pci_cap {
__u8 cfg_type; /* Identifies the structure. */
__u8 bar; /* Where to find it. */
__u8 id; /* Multiple capabilities of the same type */
- __u8 padding[2]; /* Pad to full dword. */
+ __u8 page_shift; /* Page shift for VIRTIO_PCI_CAP_SHARED_MEMORY_CFG. */
+ __u8 padding[1]; /* Pad to full dword. */
__le32 offset; /* Offset within bar. */
__le32 length; /* Length of the structure, in bytes. */
};
--
2.48.1
