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From: "Michael S. Tsirkin" <mst@redhat.com>
To: Laurent Vivier <laurent@vivier.eu>
Cc: linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org
Subject: Re: [PATCH] virtio-mmio: read[wl]()/write[wl] are already little-endian
Date: Thu, 11 Mar 2021 10:44:47 -0500	[thread overview]
Message-ID: <20210311104414-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20210309224313.956065-1-laurent@vivier.eu>

On Tue, Mar 09, 2021 at 11:43:13PM +0100, Laurent Vivier wrote:
> read[wl]()/write[wl] already access memory in little-endian mode.

But then they convert it to CPU right? We just convert it back ...

> No need to convert the value with cpu_to_leXX()/leXX_to_cpu()
> 
> Signed-off-by: Laurent Vivier <laurent@vivier.eu>
> ---
>  drivers/virtio/virtio_mmio.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
> index a286d22b6551..3f6a5588f77d 100644
> --- a/drivers/virtio/virtio_mmio.c
> +++ b/drivers/virtio/virtio_mmio.c
> @@ -168,17 +168,17 @@ static void vm_get(struct virtio_device *vdev, unsigned offset,
>  		memcpy(buf, &b, sizeof b);
>  		break;
>  	case 2:
> -		w = cpu_to_le16(readw(base + offset));
> +		w = readw(base + offset);
>  		memcpy(buf, &w, sizeof w);
>  		break;
>  	case 4:
> -		l = cpu_to_le32(readl(base + offset));
> +		l = readl(base + offset);
>  		memcpy(buf, &l, sizeof l);
>  		break;
>  	case 8:
> -		l = cpu_to_le32(readl(base + offset));
> +		l = readl(base + offset);
>  		memcpy(buf, &l, sizeof l);
> -		l = cpu_to_le32(ioread32(base + offset + sizeof l));
> +		l = ioread32(base + offset + sizeof l);
>  		memcpy(buf + sizeof l, &l, sizeof l);
>  		break;
>  	default:
> @@ -212,17 +212,17 @@ static void vm_set(struct virtio_device *vdev, unsigned offset,
>  		break;
>  	case 2:
>  		memcpy(&w, buf, sizeof w);
> -		writew(le16_to_cpu(w), base + offset);
> +		writew(w, base + offset);
>  		break;
>  	case 4:
>  		memcpy(&l, buf, sizeof l);
> -		writel(le32_to_cpu(l), base + offset);
> +		writel(l, base + offset);
>  		break;
>  	case 8:
>  		memcpy(&l, buf, sizeof l);
> -		writel(le32_to_cpu(l), base + offset);
> +		writel(l, base + offset);
>  		memcpy(&l, buf + sizeof l, sizeof l);
> -		writel(le32_to_cpu(l), base + offset + sizeof l);
> +		writel(l, base + offset + sizeof l);
>  		break;
>  	default:
>  		BUG();
> -- 
> 2.29.2

_______________________________________________
Virtualization mailing list
Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization

WARNING: multiple messages have this Message-ID (diff)
From: "Michael S. Tsirkin" <mst@redhat.com>
To: Laurent Vivier <laurent@vivier.eu>
Cc: linux-kernel@vger.kernel.org,
	virtualization@lists.linux-foundation.org,
	Jason Wang <jasowang@redhat.com>
Subject: Re: [PATCH] virtio-mmio: read[wl]()/write[wl] are already little-endian
Date: Thu, 11 Mar 2021 10:44:47 -0500	[thread overview]
Message-ID: <20210311104414-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20210309224313.956065-1-laurent@vivier.eu>

On Tue, Mar 09, 2021 at 11:43:13PM +0100, Laurent Vivier wrote:
> read[wl]()/write[wl] already access memory in little-endian mode.

But then they convert it to CPU right? We just convert it back ...

> No need to convert the value with cpu_to_leXX()/leXX_to_cpu()
> 
> Signed-off-by: Laurent Vivier <laurent@vivier.eu>
> ---
>  drivers/virtio/virtio_mmio.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
> index a286d22b6551..3f6a5588f77d 100644
> --- a/drivers/virtio/virtio_mmio.c
> +++ b/drivers/virtio/virtio_mmio.c
> @@ -168,17 +168,17 @@ static void vm_get(struct virtio_device *vdev, unsigned offset,
>  		memcpy(buf, &b, sizeof b);
>  		break;
>  	case 2:
> -		w = cpu_to_le16(readw(base + offset));
> +		w = readw(base + offset);
>  		memcpy(buf, &w, sizeof w);
>  		break;
>  	case 4:
> -		l = cpu_to_le32(readl(base + offset));
> +		l = readl(base + offset);
>  		memcpy(buf, &l, sizeof l);
>  		break;
>  	case 8:
> -		l = cpu_to_le32(readl(base + offset));
> +		l = readl(base + offset);
>  		memcpy(buf, &l, sizeof l);
> -		l = cpu_to_le32(ioread32(base + offset + sizeof l));
> +		l = ioread32(base + offset + sizeof l);
>  		memcpy(buf + sizeof l, &l, sizeof l);
>  		break;
>  	default:
> @@ -212,17 +212,17 @@ static void vm_set(struct virtio_device *vdev, unsigned offset,
>  		break;
>  	case 2:
>  		memcpy(&w, buf, sizeof w);
> -		writew(le16_to_cpu(w), base + offset);
> +		writew(w, base + offset);
>  		break;
>  	case 4:
>  		memcpy(&l, buf, sizeof l);
> -		writel(le32_to_cpu(l), base + offset);
> +		writel(l, base + offset);
>  		break;
>  	case 8:
>  		memcpy(&l, buf, sizeof l);
> -		writel(le32_to_cpu(l), base + offset);
> +		writel(l, base + offset);
>  		memcpy(&l, buf + sizeof l, sizeof l);
> -		writel(le32_to_cpu(l), base + offset + sizeof l);
> +		writel(l, base + offset + sizeof l);
>  		break;
>  	default:
>  		BUG();
> -- 
> 2.29.2


  parent reply	other threads:[~2021-03-11 15:45 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-09 22:43 [PATCH] virtio-mmio: read[wl]()/write[wl] are already little-endian Laurent Vivier
2021-03-10  3:08 ` kernel test robot
2021-03-10  3:08   ` kernel test robot
2021-03-10  3:08   ` kernel test robot
2021-03-11 15:44 ` Michael S. Tsirkin [this message]
2021-03-11 15:44   ` Michael S. Tsirkin
2021-03-11 15:55   ` Laurent Vivier
2021-03-13 17:10   ` Laurent Vivier
2021-03-14  8:26     ` Michael S. Tsirkin
2021-03-14  8:26       ` Michael S. Tsirkin

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