Re: [Xen-devel] [patch 4/4]Enable CMCI (Corrected Machine Check Error Interrupt) for Intel CPUs

[Christoph Egger <Christoph.Egger@xxxxxxx>]

On Tuesday 13 January 2009 03:12:51 Ke, Liping wrote:
> Hi, Christoph
> Please see our comments below
>
> Christoph Egger wrote:
> > On Friday 19 December 2008 07:19:16 Ke, Liping wrote:
> >> Hi, all
> >>
> >> Patch 4 is the main patch for CMCI enabling in XEN. It adds the CMCI
> >> interrupt handler, new common CMCI/MCA init process,CMCI owner judge
> >> algorithm when bring_up CPUs, CPU on/offline  and  polling
> >> mechanisms, etc
> >>
> >> Thanks & Regards,
> >> Criping
> >
> > This patch changes the public API. There's no need to change
> > struct mcinfo_extended. The marshalling technique allows to use
> > this structure as often as needed. Please undo this change.
>
> Since Intel extended msrs' number is bigger than AMD, and we can't use
> pointer and allocate memory in mca handler, so we extended it from 5 -> 10.
> We think it should not impact any of your usage.
>
> Else, we can change boundary 5->0, use a globally allocated pointer
> instead. But it seems not that necessary. How do you think about?

When I defined the API, I already knew that 5 is not enough for Intel.
So I made struct mc_info large enough to keep multiple entities in any
combination. I expected from you to fill struct mcinfo_extended two or
three times into struct mc_info  the same way as you do with
struct mcinfo_bank.   There's no (additional) allocation needed.

From your description I just read, that you don't know this marshalling 
technique.


> > struct mcinfo_global is also changed. Why can't mc_coreid not be
> > filled with the apicid ? Adding the apicid field breaks the alignment
> > causing troubles on 32bit-guest-on-64bit-hypervisor.
>
> We plan to extend the apic_id to 32 bit since 8 bit is not enough for new
> apic_id. Besides, for this problem, before sending the patch, we actually
> talked about it. Seems original structure is not 32/64 alligned. How about
> below changes?
>
> struct mcinfo_global {
>     struct mcinfo_common common; 4 byte
>
>     /* running domain at the time in error (most likely the impacted one)
> */ uint16_t mc_domid; 2 byte
>     uint32_t mc_socketid; /* physical socket of the physical core */ 4 byte
>     uint16_t mc_coreid; /* physical impacted core */ 2 byte
>     uint8_t  mc_apicid; ---change it to 4 byte
>     uint16_t mc_core_threadid; /* core thread of physical core */ 2 byte
>     uint16_t mc_vcpuid; /* virtual cpu scheduled for mc_domid */ 2 byte
>     uint64_t mc_gstatus; /* global status */ 8 byte
>     uint32_t mc_flags; 4 byte
> };
>
>
> Change to
> ------------------------>>>>>
>
> struct mcinfo_global {
>     struct mcinfo_common common; 4 byte
>
>     /* running domain at the time in error (most likely the impacted one)
> */ uint32_t mc_socketid; /* physical socket of the physical core */ 4 byte
> -----------------------------------------------------------------
>     uint16_t mc_domid; 2 byte
>     uint16_t mc_coreid; /* physical impacted core */ 2 byte
>     uint32_t  mc_apicid; ---change it to 4 byte
> -------------------------------------------------------------------
>     uint16_t mc_core_threadid; /* core thread of physical core */ 2 byte
>     uint16_t mc_vcpuid; /* virtual cpu scheduled for mc_domid */ 2 byte
>     uint32_t mc_flags; 4 byte
> --------------------------------------------------------------------------
>     uint64_t mc_gstatus; /* global status */ 8 byte
> };

Your proposed change fixes the alignment problem, but it doesn't answer my
question: Why is mc_apicid needed at all since the CPU core is already
identified by mc_coreid ?

Christoph



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