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Date: Tue, 3 Apr 2012 16:16:02 +0300
From: Alon Levy <alevy@redhat.com>
Message-ID: <20120403131602.GQ20067@garlic.redhat.com>
References: <1333455707-3534-1-git-send-email-hdegoede@redhat.com>
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In-Reply-To: <1333455707-3534-1-git-send-email-hdegoede@redhat.com>
Subject: Re: [Qemu-devel] [PATCH] usb-ehci: Ensure frindex writes leave a
 valid frindex value
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To: Hans de Goede <hdegoede@redhat.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>, qemu-devel@nongnu.org

On Tue, Apr 03, 2012 at 02:21:47PM +0200, Hans de Goede wrote:
> frindex is a 14 bits counter, so bits 31-14 should always be 0, and
> after the commit titled "usb-ehci: frindex always is a 14 bits counter"
> we rely on frindex always being a multiple of 8. I've not seen this in
> practice, but theoretically a guest can write a value >= 0x4000 or a value
> which is not a multiple of 8 value to frindex, this patch ensures that
> things will still work when that happens.

Acked-by: Alon Levy <alevy@redhat.com>

> 
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> ---
>  hw/usb/hcd-ehci.c |    4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/hw/usb/hcd-ehci.c b/hw/usb/hcd-ehci.c
> index 64b58e3..8865b4e 100644
> --- a/hw/usb/hcd-ehci.c
> +++ b/hw/usb/hcd-ehci.c
> @@ -1102,6 +1102,10 @@ static void ehci_mem_writel(void *ptr, target_phys_addr_t addr, uint32_t val)
>          val &= USBINTR_MASK;
>          break;
>  
> +    case FRINDEX:
> +        val &= 0x00003ff8; /* frindex is 14bits and always a multiple of 8 */
> +        break;
> +
>      case CONFIGFLAG:
>          val &= 0x1;
>          if (val) {
> -- 
> 1.7.9.3
> 
>