Re: [PATCH 1/5] BIOS changes for configuring irq0->inti2 override (v4)

From: "Sebastian Herbszt" <herbszt@gmx.de>
To: "Beth Kon" <eak@us.ibm.com>, <avi@redhat.com>
Cc: <kvm@vger.kernel.org>
Subject: Re: [PATCH 1/5] BIOS changes for configuring irq0->inti2 override (v4)
Date: Thu, 11 Jun 2009 22:50:14 +0200	[thread overview]
Message-ID: <96E2F18C325F48788FEB591C6547B4B5@FSCPC> (raw)
In-Reply-To: <1244731365-32069-1-git-send-email-eak@us.ibm.com>

Beth Kon wrote:
> These patches resolve the irq0->inti2 override issue, and get the hpet working
> on kvm.
> 
> Override and HPET changes are sent as a series because HPET depends on the
> override. Win2k8 expects the HPET interrupt on inti2, regardless of whether
> an override exists in the BIOS. And the HPET spec states that in legacy mode,
> timer interrupt is on inti2.
> 
> The irq0->inti2 override will always be used unless the kernel cannot do irq
> routing (i.e., compatibility with old kernels). So if the kernel is capable,
> userspace sets up irq0->inti2 via the irq routing interface, and adds the
> irq0->inti2 override to the MADT interrupt source override table,
> and the mp table (for the no-acpi case).
> 
> Changes from v3:
> 
> - changes based on comments from Avi and Gleb.
> - corrected legacy enable/disable for in-kernel PIT. The code now best
>  approximates a multiplexer that disables PIT interrupts when HPET is 
>  in legacy mode (as described by HPET spec). Any changes to the PIT that 
>  may occur while HPET is operating in legacy mode are saved, so if 
>  HPET leaves legacy mode, the PIT is just reenabled, with mode set     
>  to whatever the last setting from guest was. Legacy mode is disabled
>  at least during crash and shutdown (in Linux), so this needs to be 
>  handled properly.
> 
> 
> ---
> kvm/bios/rombios32.c |   60 ++++++++++++++++++++++++++++++++++++-------------
> 1 files changed, 44 insertions(+), 16 deletions(-)

What about the mptable entry count?
Think it would need something like

#ifdef BX_QEMU
  if (irq0_override)
    putle16(&q, smp_cpus + 17); /* entry count */
  else
    putle16(&q, smp_cpus + 18); /* entry count */
#else
  putle16(&q, smp_cpus + 18); /* entry count */
#endif

Your patch "Fix non-ACPI Timer Interrupt Routing - v3" [1] included such a change.

[1] http://lists.gnu.org/archive/html/qemu-devel/2009-04/msg01396.html

- Sebastian