[Qemu-devel] [PATCH] rtl8139: fix regression in TxStatus/TxAddr read

[Qemu-devel] [PATCH] rtl8139: fix regression in TxStatus/TxAddr read

[Avi Kivity]

Commit afe0a595356192 added byte reads for TxStatus/TxAddr, but
broke 32-bit reads; the mask generation

   (1 << (8 * size)) - 1

is unspecified in C for size >= sizeof(int), and in fact returns 0
on x86.

Fix by using a larger type.

Fixes (at least) Fedora 9 i386 with -machine kernel_irqchip=on.  I
didn't see it with the qemu APIC implementation; may be due to timing
or (more likely) a tester error.

Signed-off-by: Avi Kivity <avi@redhat.com>
---
 hw/rtl8139.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/rtl8139.c b/hw/rtl8139.c
index 4d0f5ba..eb22d04 100644
--- a/hw/rtl8139.c
+++ b/hw/rtl8139.c
@@ -2500,7 +2500,7 @@ static uint32_t rtl8139_TxStatus_TxAddr_read(RTL8139State *s, uint32_t regs[],
     case 1: /* fall through */
     case 2: /* fall through */
     case 4:
-        ret = (regs[reg] >> offset * 8) & ((1 << (size * 8)) - 1);
+        ret = (regs[reg] >> offset * 8) & (((uint64_t)1 << (size * 8)) - 1);
         DPRINTF("TxStatus/TxAddr[%d] read addr=0x%x size=0x%x val=0x%08x\n",
                 reg, addr, size, ret);
         break;
-- 
1.7.10.1

Re: [Qemu-devel] [PATCH] rtl8139: fix regression in TxStatus/TxAddr read

[Michael S. Tsirkin]

On Mon, May 07, 2012 at 03:00:45PM +0300, Avi Kivity wrote:
> Commit afe0a595356192 added byte reads for TxStatus/TxAddr, but
> broke 32-bit reads; the mask generation
> 
>    (1 << (8 * size)) - 1
> 
> is unspecified in C for size >= sizeof(int), and in fact returns 0
> on x86.
> 
> Fix by using a larger type.
> 
> Fixes (at least) Fedora 9 i386 with -machine kernel_irqchip=on.  I
> didn't see it with the qemu APIC implementation; may be due to timing
> or (more likely) a tester error.
> 
> Signed-off-by: Avi Kivity <avi@redhat.com>

Applied, thanks

> ---
>  hw/rtl8139.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/hw/rtl8139.c b/hw/rtl8139.c
> index 4d0f5ba..eb22d04 100644
> --- a/hw/rtl8139.c
> +++ b/hw/rtl8139.c
> @@ -2500,7 +2500,7 @@ static uint32_t rtl8139_TxStatus_TxAddr_read(RTL8139State *s, uint32_t regs[],
>      case 1: /* fall through */
>      case 2: /* fall through */
>      case 4:
> -        ret = (regs[reg] >> offset * 8) & ((1 << (size * 8)) - 1);
> +        ret = (regs[reg] >> offset * 8) & (((uint64_t)1 << (size * 8)) - 1);
>          DPRINTF("TxStatus/TxAddr[%d] read addr=0x%x size=0x%x val=0x%08x\n",
>                  reg, addr, size, ret);
>          break;
> -- 
> 1.7.10.1