From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43)
	id 1MaW7P-00089Y-4I
	for qemu-devel@nongnu.org; Mon, 10 Aug 2009 10:44:59 -0400
Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43)
	id 1MaW7K-00085q-I9
	for qemu-devel@nongnu.org; Mon, 10 Aug 2009 10:44:58 -0400
Received: from [199.232.76.173] (port=50109 helo=monty-python.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1MaW7K-000850-8U
	for qemu-devel@nongnu.org; Mon, 10 Aug 2009 10:44:54 -0400
Received: from qw-out-1920.google.com ([74.125.92.149]:46263)
	by monty-python.gnu.org with esmtp (Exim 4.60)
	(envelope-from <anthony@codemonkey.ws>) id 1MaW7J-0006v9-MA
	for qemu-devel@nongnu.org; Mon, 10 Aug 2009 10:44:53 -0400
Received: by qw-out-1920.google.com with SMTP id 5so1053681qwc.4
	for <qemu-devel@nongnu.org>; Mon, 10 Aug 2009 07:44:49 -0700 (PDT)
Message-ID: <4A80325E.9020505@codemonkey.ws>
Date: Mon, 10 Aug 2009 09:44:46 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
MIME-Version: 1.0
Subject: Re: [Qemu-devel] [PATCH 1/2] Make HPET Legacy Only
References: <1249049162-685-1-git-send-email-eak@us.ibm.com>
In-Reply-To: <1249049162-685-1-git-send-email-eak@us.ibm.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
List-Id: qemu-devel.nongnu.org
List-Unsubscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.gnu.org/pipermail/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Beth Kon <eak@us.ibm.com>
Cc: qemu-devel@nongnu.org

Beth Kon wrote:
> Because of unavailability of IOAPIC interrupt lines, HPET currently 
> supports only legacy mode, where the legacy timer interrupt (inti2) is
> used. This patch makes this explicit by reducing the number of timers 
> supported by HPET to 2 (the 2 legacy timers) and advertising no
> available IOAPIC interrupt lines.
>
> This patch also adds a check, suggested by Andriy Gapon, to ensure that
> the interrupt chosen by the guest is one of those advertised by the HPET
> as available. This is currently a noop since HPET advertises none as 
> available, but in the event of future expansion and availability of 
> IOAPIC interrupt lines, or implementation of level-triggered interrupts
> that can share interrupt lines, this code will be in place. 
>
> This subset of HPET capability (legacy-only) is reasonable, since the 
> basic operation of linux and windows only uses the HPET in legacy mode, 
> at least that's what all my testing so far has shown. Only userspace
> access to the hpet would use non-legacy timers.
>
>
>
>
> diff --git a/hw/hpet.c b/hw/hpet.c
> index 01b10aa..56fa27c 100644
> --- a/hw/hpet.c
> +++ b/hw/hpet.c
> @@ -47,12 +47,16 @@ uint32_t hpet_in_legacy_mode(void)
>          return 0;
>  }
>  
> -static uint32_t timer_int_route(struct HPETTimer *timer)
> -{
> -    uint32_t route;
> -    route = (timer->config & HPET_TN_INT_ROUTE_MASK) >> HPET_TN_INT_ROUTE_SHIFT;
> -    return route;
> -}
> +/* future code for when non-legacy interrupts are supported
> + * (when spare ioapic interrupts are available)
> + * static uint32_t timer_int_route(struct HPETTimer *timer)
> + * {
> + *    uint32_t route;
> + *    route = (timer->config & HPET_TN_INT_ROUTE_CNF_MASK) 
> + *                              >> HPET_TN_INT_ROUTE_CNF_SHIFT;
> + *    return route;
> + *}
> + */
>   

Please don't introduce dead code.  It will just rot.  A comment would 
suffice.

Regards,

Anthony Liguori