linux-kernel - Re: [PATCH] virtio_mmio: fix endian-ness for mmio

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Message-ID: <20150309083941.GA22567@redhat.com>
Date:	Mon, 9 Mar 2015 09:39:41 +0100
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	Rusty Russell <rusty@...tcorp.com.au>,
	virtualization@...ts.linux-foundation.org,
	Pawel Moll <pawel.moll@....com>
Subject: Re: [PATCH] virtio_mmio: fix endian-ness for mmio

On Thu, Mar 05, 2015 at 10:54:31PM +0100, Michael S. Tsirkin wrote:
> Going over the virtio mmio code, I noticed that it doesn't correctly
> return device config values in LE format when using virtio 1.0.
> Borrow code from virtio_pci_modern to do this correctly.
> 
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>

Pawel, could you review and ack please?
It'd be unfortunate if we released a version
with incorrect endian-ness.

> ---
> 
> Note: untested: QEMU doesn't support virtio 1.0 for virtio-mmio.
> Pawel, could you please confirm this patch makes sense?
> 
>  drivers/virtio/virtio_mmio.c | 79 +++++++++++++++++++++++++++++++++++++++-----
>  1 file changed, 71 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
> index cad5698..0375456 100644
> --- a/drivers/virtio/virtio_mmio.c
> +++ b/drivers/virtio/virtio_mmio.c
> @@ -156,22 +156,85 @@ static void vm_get(struct virtio_device *vdev, unsigned offset,
>  		   void *buf, unsigned len)
>  {
>  	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
> -	u8 *ptr = buf;
> -	int i;
> +	void __iomem *base = vm_dev->base + VIRTIO_MMIO_CONFIG;
> +	u8 b;
> +	__le16 w;
> +	__le32 l;
>  
> -	for (i = 0; i < len; i++)
> -		ptr[i] = readb(vm_dev->base + VIRTIO_MMIO_CONFIG + offset + i);
> +	if (vm_dev->version == 1) {
> +		u8 *ptr = buf;
> +		int i;
> +
> +		for (i = 0; i < len; i++)
> +			ptr[i] = readb(base + offset + i);
> +		return;
> +	}
> +
> +	switch (len) {
> +	case 1:
> +		b = readb(base + offset);
> +		memcpy(buf, &b, sizeof b);
> +		break;
> +	case 2:
> +		w = cpu_to_le16(readw(base + offset));
> +		memcpy(buf, &w, sizeof w);
> +		break;
> +	case 4:
> +		l = cpu_to_le32(readl(base + offset));
> +		memcpy(buf, &l, sizeof l);
> +		break;
> +	case 8:
> +		l = cpu_to_le32(readl(base + offset));
> +		memcpy(buf, &l, sizeof l);
> +		l = cpu_to_le32(ioread32(base + offset + sizeof l));
> +		memcpy(buf + sizeof l, &l, sizeof l);
> +		break;
> +	default:
> +		BUG();
> +	}
>  }
>  
>  static void vm_set(struct virtio_device *vdev, unsigned offset,
>  		   const void *buf, unsigned len)
>  {
>  	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
> -	const u8 *ptr = buf;
> -	int i;
> +	void __iomem *base = vm_dev->base + VIRTIO_MMIO_CONFIG;
> +	u8 b;
> +	__le16 w;
> +	__le32 l;
>  
> -	for (i = 0; i < len; i++)
> -		writeb(ptr[i], vm_dev->base + VIRTIO_MMIO_CONFIG + offset + i);
> +	if (vm_dev->version == 1) {
> +		const u8 *ptr = buf;
> +		int i;
> +
> +		for (i = 0; i < len; i++)
> +			writeb(ptr[i], base + offset + i);
> +
> +		return;
> +	}
> +
> +	switch (len) {
> +	case 1:
> +		memcpy(&b, buf, sizeof b);
> +		writeb(b, base + offset);
> +		break;
> +	case 2:
> +		memcpy(&w, buf, sizeof w);
> +		writew(le16_to_cpu(w), base + offset);
> +		break;
> +	case 4:
> +		memcpy(&l, buf, sizeof l);
> +		writel(le32_to_cpu(l), base + offset);
> +		break;
> +	case 8:
> +		memcpy(&l, buf, sizeof l);
> +		writel(le32_to_cpu(l), base + offset);
> +		memcpy(&l, buf + sizeof l, sizeof l);
> +		writel(le32_to_cpu(l), base + offset + sizeof l);
> +		break;
> +	default:
> +		BUG();
> +	}
>  }
>  
>  static u8 vm_get_status(struct virtio_device *vdev)
> -- 
> MST
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