Re: [PATCH 2/3] Pnp bios gdt fix

[Zachary Amsden <zach@vmware.com>]

Zachary Amsden wrote:

> PnP BIOS for x86 is part of drivers, so I missed it in the initial
> GDT page alignment patch.  Kudos to Andrew for fixing that.
> Unfortunately, fixing the build introduced a kernel panic when
> trying to setup the as of yet unallocated GDTs for the APs.
> This fixes the problem by setting only the BSP's GDT, then copying
> the PnP segments back to the cpu_gdt_table template.
>
>  

Bogus patch!  I was just getting lucky and not running PnP BIOS code on 
the AP's -- until now.  Turns out the fix and the bug were much 
simpler.  Please apply this instead.


PnP BIOS for x86 is part of drivers, so I missed it in the initial
GDT page alignment patch.  Kudos to Andrew for fixing that.
Unfortunately, fixing the build introduced a kernel panic when
trying to setup the as of yet unallocated GDTs for the APs.

I totally misdiagnosed this.  The problem happens only
when NR_CPUS > physical CPUs.  Fix is to ignore missing GDT's.

Signed-off-by: Zachary Amsden <zach@vmware.com>
Index: linux-2.6.14-rc2/drivers/pnp/pnpbios/bioscalls.c
===================================================================
--- linux-2.6.14-rc2.orig/drivers/pnp/pnpbios/bioscalls.c	2005-09-28 15:57:42.000000000 -0700
+++ linux-2.6.14-rc2/drivers/pnp/pnpbios/bioscalls.c	2005-09-28 15:59:37.000000000 -0700
@@ -537,6 +537,8 @@ void pnpbios_calls_init(union pnp_bios_i
 	_set_limit((char *)&bad_bios_desc, 4095 - (0x40 << 4));
 	for(i=0; i < NR_CPUS; i++)
 	{
+		if (!get_cpu_gdt_table(i))
+			continue;
 		Q2_SET_SEL(i, PNP_CS32, &pnp_bios_callfunc, 64 * 1024);
 		Q_SET_SEL(i, PNP_CS16, header->fields.pm16cseg, 64 * 1024);
 		Q_SET_SEL(i, PNP_DS, header->fields.pm16dseg, 64 * 1024);