Re: [Xen-ia64-devel] Re: [PATCH] Fix mca handler so as not to destroy ar

[SUZUKI Kazuhiro <kaz@xxxxxxxxxxxxxx>]

Hi,

I think gp passed from SAL is changed to a virtual address by
DATA_PA_TO_VA() in VIRTUAL_MODE_ENTER().

#define DATA_PA_TO_VA(addr,temp)                        \
        mov     temp    = 0xf   ;;                      \
        dep     addr    = temp, addr, 60, 4

Could you please explain the issue a little more in detail?

Thanks,
KAZ


From: Isaku Yamahata <yamahata@xxxxxxxxxxxxx>
Subject: Re: [Xen-ia64-devel] Re: [PATCH] Fix mca handler so as not to destroy 
ar
Date: Thu, 7 Aug 2008 19:30:11 +0900

> On Tue, Aug 05, 2008 at 02:19:06PM +0900, Isaku Yamahata wrote:
> > On Tue, Aug 05, 2008 at 12:37:17PM +0900, Isaku Yamahata wrote:
> > > 
> > > Hi Kazu. Sorry for late alert.
> > > VIRTUAL_MODE_ENTER() still refers ar.k6.
> > > Could you fix it?
> > 
> > One more.
> > Before pinning down vpd and vhpt, it's necessary to
> > make sure that they doesn't overlap with stack like __vmxswitch_rr7()
> > and ia64_new_rr7().
> 
> And more.
> VIRTUAL_MODE_ENTER() sets gp (r1) to ia64_os_mca_virtual_begin
> and then call ia64_mca_ucmc_handler().
> It this correct? It looks like that accessing global variable
> in ia64_mca_ucmc_handler() results in rondom place access.
> 
> Linux has the related fix. What do you think?
> 
> commit f5a3f3dc189485d607fbd42678cc23958acc0a6e
> Author: Zou Nan hai <nanhai.zou@xxxxxxxxx>
> Date:   Thu Sep 14 08:25:15 2006 +0800
> 
>     [IA64] Make gp value point to Region 5 in mca handler
>     
>     MCA dispatch code take physical address of GP passed from SAL, then call
>     DATA_PA_TO_VA twice on GP before call into C code.  The first time is
>     in ia64_set_kernel_register, the second time is in VIRTUAL_MODE_ENTER.
>     The gp is changed to a virtual address in region 7 because DATA_PA_TO_VA
>     is implemented by dep instruction.
>     
>     However when notify blocks were called from MCA handler code, because
>     notify blocks are supported by callback function pointers, gp value
>     value was switched to region 5 again.
>     
>     The patch set gp register to kernel gp of region 5 at entry of MCA
>     dispatch.
>     
>     Signed-off-by: Zou Nan hai <nanhai.zou@xxxxxxxxx>
>     Signed-off-by: Tony Luck <tony.luck@xxxxxxxxx>
> 
> 
> -- 
> yamahata

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