Re: [Qemu-devel] [PATCH] ignore reads to the EOI register.

[Aurelien Jarno <aurelien@aurel32.net>]

On Wed, Mar 26, 2008 at 09:57:16PM -0300, Glauber Costa wrote:
> They seem legal in real hardware, even though the EOI
> is a write-only register. By "legal" I mean they are completely
> ignored, but at least, don't cause any bits to be set at ESR.
> 
> Without this patch, some (very recent) linux git trees will fail
> to boot in i386.
> 
> This is generated from kvm-userspace, but should apply well to
> plain qemu too.
> 
> Signed-off-by: Glauber Costa <gcosta@redhat.com>
> ---
>  qemu/hw/apic.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
> 
> diff --git a/qemu/hw/apic.c b/qemu/hw/apic.c
> index 92248dd..4102493 100644
> --- a/qemu/hw/apic.c
> +++ b/qemu/hw/apic.c
> @@ -615,6 +615,8 @@ static uint32_t apic_mem_readl(void *opaque, target_phys_addr_t addr)
>          /* ppr */
>          val = apic_get_ppr(s);
>          break;
> +    case 0x0b:
> +        break;

While I agree the guest should not care of the value (it should actually
not read it), wouldn't it be safer to return a default value (0 ?) 
instead of an initialized value?

-- 
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