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    Subject[PATCH 05/19] virtio: Implement get_shm_region for MMIO transport
    Date
    From: Sebastien Boeuf <sebastien.boeuf@intel.com>

    On MMIO a new set of registers is defined for finding SHM
    regions. Add their definitions and use them to find the region.

    Cc: kvm@vger.kernel.org
    Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
    ---
    drivers/virtio/virtio_mmio.c | 32 ++++++++++++++++++++++++++++++++
    include/uapi/linux/virtio_mmio.h | 11 +++++++++++
    2 files changed, 43 insertions(+)

    diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
    index e09edb5c5e06..5c07985c8cb8 100644
    --- a/drivers/virtio/virtio_mmio.c
    +++ b/drivers/virtio/virtio_mmio.c
    @@ -500,6 +500,37 @@ static const char *vm_bus_name(struct virtio_device *vdev)
    return vm_dev->pdev->name;
    }

    +static bool vm_get_shm_region(struct virtio_device *vdev,
    + struct virtio_shm_region *region, u8 id)
    +{
    + struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
    + u64 len, addr;
    +
    + /* Select the region we're interested in */
    + writel(id, vm_dev->base + VIRTIO_MMIO_SHM_SEL);
    +
    + /* Read the region size */
    + len = (u64) readl(vm_dev->base + VIRTIO_MMIO_SHM_LEN_LOW);
    + len |= (u64) readl(vm_dev->base + VIRTIO_MMIO_SHM_LEN_HIGH) << 32;
    +
    + region->len = len;
    +
    + /* Check if region length is -1. If that's the case, the shared memory
    + * region does not exist and there is no need to proceed further.
    + */
    + if (len == ~(u64)0) {
    + return false;
    + }
    +
    + /* Read the region base address */
    + addr = (u64) readl(vm_dev->base + VIRTIO_MMIO_SHM_BASE_LOW);
    + addr |= (u64) readl(vm_dev->base + VIRTIO_MMIO_SHM_BASE_HIGH) << 32;
    +
    + region->addr = addr;
    +
    + return true;
    +}
    +
    static const struct virtio_config_ops virtio_mmio_config_ops = {
    .get = vm_get,
    .set = vm_set,
    @@ -512,6 +543,7 @@ static const struct virtio_config_ops virtio_mmio_config_ops = {
    .get_features = vm_get_features,
    .finalize_features = vm_finalize_features,
    .bus_name = vm_bus_name,
    + .get_shm_region = vm_get_shm_region,
    };


    diff --git a/include/uapi/linux/virtio_mmio.h b/include/uapi/linux/virtio_mmio.h
    index c4b09689ab64..0650f91bea6c 100644
    --- a/include/uapi/linux/virtio_mmio.h
    +++ b/include/uapi/linux/virtio_mmio.h
    @@ -122,6 +122,17 @@
    #define VIRTIO_MMIO_QUEUE_USED_LOW 0x0a0
    #define VIRTIO_MMIO_QUEUE_USED_HIGH 0x0a4

    +/* Shared memory region id */
    +#define VIRTIO_MMIO_SHM_SEL 0x0ac
    +
    +/* Shared memory region length, 64 bits in two halves */
    +#define VIRTIO_MMIO_SHM_LEN_LOW 0x0b0
    +#define VIRTIO_MMIO_SHM_LEN_HIGH 0x0b4
    +
    +/* Shared memory region base address, 64 bits in two halves */
    +#define VIRTIO_MMIO_SHM_BASE_LOW 0x0b8
    +#define VIRTIO_MMIO_SHM_BASE_HIGH 0x0bc
    +
    /* Configuration atomicity value */
    #define VIRTIO_MMIO_CONFIG_GENERATION 0x0fc

    --
    2.20.1
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