linux-kernel - Re: [PATCH 05/19] virtio: Implement get_shm

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Date:   Tue, 27 Aug 2019 10:39:43 +0200
From:   Cornelia Huck <cohuck@...hat.com>
To:     Vivek Goyal <vgoyal@...hat.com>
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-nvdimm@...ts.01.org, virtio-fs@...hat.com, miklos@...redi.hu,
        stefanha@...hat.com, dgilbert@...hat.com,
        Sebastien Boeuf <sebastien.boeuf@...el.com>,
        kvm@...r.kernel.org
Subject: Re: [PATCH 05/19] virtio: Implement get_shm_region for MMIO
 transport

On Wed, 21 Aug 2019 13:57:06 -0400
Vivek Goyal <vgoyal@...hat.com> wrote:

> From: Sebastien Boeuf <sebastien.boeuf@...el.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@...r.kernel.org
> Signed-off-by: Sebastien Boeuf <sebastien.boeuf@...el.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;
> +	}

I think the curly braces should be dropped here.

> +
> +	/* 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,

Reviewed-by: Cornelia Huck <cohuck@...hat.com>