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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