Introduce VIRTIO_F_SHM_PAGE_SIZE, a feature bit which indicates that the
transport provides the page size for SHM regions.

Signed-off-by: Sergio Lopez <slp@redhat.com>
---
 drivers/virtio/virtio_pci_modern.c | 3 +++
 drivers/virtio/virtio_ring.c       | 2 ++
 include/uapi/linux/virtio_config.h | 7 ++++++-
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
index d7aeb2e50a3c499dfb68d58cb89b829ea2e50454..ab0e1d9148057c431676bfacfe5f68cc97eebb12 100644
--- a/drivers/virtio/virtio_pci_modern.c
+++ b/drivers/virtio/virtio_pci_modern.c
@@ -367,6 +367,9 @@ static void vp_transport_features(struct virtio_device *vdev, u64 features)
 
 	if (features & BIT_ULL(VIRTIO_F_ADMIN_VQ))
 		__virtio_set_bit(vdev, VIRTIO_F_ADMIN_VQ);
+
+	if (features & BIT_ULL(VIRTIO_F_SHM_PAGE_SIZE))
+		__virtio_set_bit(vdev, VIRTIO_F_SHM_PAGE_SIZE);
 }
 
 static int __vp_check_common_size_one_feature(struct virtio_device *vdev, u32 fbit,
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index fdd2d2b07b5a2aca864bc917306536685afb66a6..d853d5cf7e553be8bbe0ff461dc7312b258c6e58 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -2983,6 +2983,8 @@ void vring_transport_features(struct virtio_device *vdev)
 			break;
 		case VIRTIO_F_NOTIFICATION_DATA:
 			break;
+		case VIRTIO_F_SHM_PAGE_SIZE:
+			break;
 		default:
 			/* We don't understand this bit. */
 			__virtio_clear_bit(vdev, i);
diff --git a/include/uapi/linux/virtio_config.h b/include/uapi/linux/virtio_config.h
index 2445f365bce74b4e926c6929322b269252ab6830..3171e3792263c2cd472ac09da18e593ab400751d 100644
--- a/include/uapi/linux/virtio_config.h
+++ b/include/uapi/linux/virtio_config.h
@@ -52,7 +52,7 @@
  * rest are per-device feature bits.
  */
 #define VIRTIO_TRANSPORT_F_START	28
-#define VIRTIO_TRANSPORT_F_END		42
+#define VIRTIO_TRANSPORT_F_END		43
 
 #ifndef VIRTIO_CONFIG_NO_LEGACY
 /* Do we get callbacks when the ring is completely used, even if we've
@@ -120,4 +120,9 @@
  */
 #define VIRTIO_F_ADMIN_VQ		41
 
+/*
+ * This feature indicates that the transport provides the SHM page size.
+ */
+#define VIRTIO_F_SHM_PAGE_SIZE		42
+
 #endif /* _UAPI_LINUX_VIRTIO_CONFIG_H */

-- 
2.48.1

On 2/14/25 18:16, Sergio Lopez wrote:
> Introduce VIRTIO_F_SHM_PAGE_SIZE, a feature bit which indicates that the
> transport provides the page size for SHM regions.
> 
> Signed-off-by: Sergio Lopez <slp@redhat.com>
> ---
>  drivers/virtio/virtio_pci_modern.c | 3 +++
>  drivers/virtio/virtio_ring.c       | 2 ++
>  include/uapi/linux/virtio_config.h | 7 ++++++-
>  3 files changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
> index d7aeb2e50a3c499dfb68d58cb89b829ea2e50454..ab0e1d9148057c431676bfacfe5f68cc97eebb12 100644
> --- a/drivers/virtio/virtio_pci_modern.c
> +++ b/drivers/virtio/virtio_pci_modern.c
> @@ -367,6 +367,9 @@ static void vp_transport_features(struct virtio_device *vdev, u64 features)
>  
>  	if (features & BIT_ULL(VIRTIO_F_ADMIN_VQ))
>  		__virtio_set_bit(vdev, VIRTIO_F_ADMIN_VQ);
> +
> +	if (features & BIT_ULL(VIRTIO_F_SHM_PAGE_SIZE))
> +		__virtio_set_bit(vdev, VIRTIO_F_SHM_PAGE_SIZE);
>  }
>  
>  static int __vp_check_common_size_one_feature(struct virtio_device *vdev, u32 fbit,
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index fdd2d2b07b5a2aca864bc917306536685afb66a6..d853d5cf7e553be8bbe0ff461dc7312b258c6e58 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -2983,6 +2983,8 @@ void vring_transport_features(struct virtio_device *vdev)
>  			break;
>  		case VIRTIO_F_NOTIFICATION_DATA:
>  			break;
> +		case VIRTIO_F_SHM_PAGE_SIZE:
> +			break;
>  		default:
>  			/* We don't understand this bit. */
>  			__virtio_clear_bit(vdev, i);
> diff --git a/include/uapi/linux/virtio_config.h b/include/uapi/linux/virtio_config.h
> index 2445f365bce74b4e926c6929322b269252ab6830..3171e3792263c2cd472ac09da18e593ab400751d 100644
> --- a/include/uapi/linux/virtio_config.h
> +++ b/include/uapi/linux/virtio_config.h
> @@ -52,7 +52,7 @@
>   * rest are per-device feature bits.
>   */
>  #define VIRTIO_TRANSPORT_F_START	28
> -#define VIRTIO_TRANSPORT_F_END		42
> +#define VIRTIO_TRANSPORT_F_END		43
>  
>  #ifndef VIRTIO_CONFIG_NO_LEGACY
>  /* Do we get callbacks when the ring is completely used, even if we've
> @@ -120,4 +120,9 @@
>   */
>  #define VIRTIO_F_ADMIN_VQ		41
>  
> +/*
> + * This feature indicates that the transport provides the SHM page size.
> + */
> +#define VIRTIO_F_SHM_PAGE_SIZE		42
> +
>  #endif /* _UAPI_LINUX_VIRTIO_CONFIG_H */
> 

Reviewed-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>

-- 
Best regards,
Dmitry