* [help] rsp in case of interrupt/exception in ring0
@ 2010-02-24 3:39 Mukesh Rathor
2010-02-24 8:35 ` Jan Beulich
0 siblings, 1 reply; 3+ messages in thread
From: Mukesh Rathor @ 2010-02-24 3:39 UTC (permalink / raw)
To: Xen-devel@lists.xensource.com
Hi,
can someone help me understand this.
When a cpu is in hyp code and int/exception comes in, how/where is rsp
saved? According to intel manual if there's no ring transition, then
the cpu doesn't save ss/rsp.
Following trail from entry.S to show_registers(), I don't see where
regs->rsp is loaded, yet show_registers() displays it happily.
show_stack() uses it.
This also means that regs->rsp is actually going
to prev frame where orig hyp function was executing.
thanks,
Mukesh
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [help] rsp in case of interrupt/exception in ring0
2010-02-24 3:39 [help] rsp in case of interrupt/exception in ring0 Mukesh Rathor
@ 2010-02-24 8:35 ` Jan Beulich
2010-02-25 4:42 ` Mukesh Rathor
0 siblings, 1 reply; 3+ messages in thread
From: Jan Beulich @ 2010-02-24 8:35 UTC (permalink / raw)
To: Xen-devel@lists.xensource.com, Mukesh Rathor
>>> Mukesh Rathor <mukesh.rathor@oracle.com> 24.02.10 04:39 >>>
>When a cpu is in hyp code and int/exception comes in, how/where is rsp
>saved? According to intel manual if there's no ring transition, then
>the cpu doesn't save ss/rsp.
As you're apparently talking about x86-64, you probably simply read
the wrong (32-bit) part of the manual. On 64-bits, ss:rsp are always
getting saved, no matter whether there's a ring transition.
Jan
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [help] rsp in case of interrupt/exception in ring0
2010-02-24 8:35 ` Jan Beulich
@ 2010-02-25 4:42 ` Mukesh Rathor
0 siblings, 0 replies; 3+ messages in thread
From: Mukesh Rathor @ 2010-02-25 4:42 UTC (permalink / raw)
To: Jan Beulich; +Cc: Xen-devel@lists.xensource.com
On Wed, 24 Feb 2010 08:35:31 +0000
"Jan Beulich" <JBeulich@novell.com> wrote:
> >>> Mukesh Rathor <mukesh.rathor@oracle.com> 24.02.10 04:39 >>>
> >When a cpu is in hyp code and int/exception comes in, how/where is
> >rsp saved? According to intel manual if there's no ring transition,
> >then the cpu doesn't save ss/rsp.
>
> As you're apparently talking about x86-64, you probably simply read
> the wrong (32-bit) part of the manual. On 64-bits, ss:rsp are always
> getting saved, no matter whether there's a ring transition.
>
You are right, few pages later, it talks about 64. Usually, they'll say
something about things being different on 64bit. Anyways. I'll email intel
docs to fix it...
thanks,
Mukesh
^ permalink raw reply [flat|nested] 3+ messages in thread
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2010-02-24 3:39 [help] rsp in case of interrupt/exception in ring0 Mukesh Rathor
2010-02-24 8:35 ` Jan Beulich
2010-02-25 4:42 ` Mukesh Rathor
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