Re: [PATCH] kvm: bios: end AP boot code execution in rombios

["Yang, Sheng" <sheng.yang@intel.com>]

On Monday 18 August 2008 10:33:11 Anthony Liguori wrote:
> Sebastian Herbszt wrote:
> > Jump to rombios before executing the halt loop.
>
> Why?  More importantly, why is this specific to KVM?

The bios copy AP boot up code to 0x10000 now in KVM, so it can be 
overwrite by userspace program like grub. I found it caused 
stop/cont/info cpus in grub corrupt AP. Please refer to "
KVM: Fix exiting from HLT emulation with MP_STATE_HALTED"
(well, I found the patch duplicated with Marcelo's patch later, then 
drop it...)

Yeah, I am agree this should not be a specific issue to KVM.

-- 
regards
Yang, Sheng
>
> Regards,
>
> Anthony Liguori
>
> > Signed-off-by: Sebastian Herbszt <herbszt@gmx.de>
> >
> > diff -uNrp a/bios/rombios32start.S b/bios/rombios32start.S
> > --- a/bios/rombios32start.S	2008-08-17 23:30:42.000000000 +0200
> > +++ b/bios/rombios32start.S	2008-08-17 23:38:42.000000000 +0200
> > @@ -40,6 +40,7 @@ _start:
> >
> >    .code16
> >  smp_ap_boot_code_start:
> > +  cli
> >    xor %ax, %ax
> >    mov %ax, %ds
> >    xor %eax, %eax
> > @@ -60,6 +61,7 @@ smp_ap_boot_code_start:
> >  12:
> >
> >    incw CPU_COUNT_ADDR
> > +  ljmp $0xe000, $(1f-_start)
> >  1:
> >    hlt
> >    jmp 1b
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe kvm" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at 
> > http://vger.kernel.org/majordomo-info.html
>
> --
> To unsubscribe from this list: send the line "unsubscribe kvm" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html