RE: [Xen-ia64-devel][Patch]Add two PAL calls which fix SMPwindowsinstallation crashing bug

["Xu, Anthony" <anthony.xu@xxxxxxxxx>]

Agree, Tristan's GFW can resolve installation issue and implement cpu hotplug 
as well,

Anthony

>-----Original Message-----
>From: Kouya SHIMURA [mailto:kouya@xxxxxxxxxxxxxx]
>Sent: 2007年4月5日 12:33
>To: tgingold@xxxxxxx
>Cc: Alex Williamson; Zhang, Xing Z; xen-ia64-devel; Xu, Anthony
>Subject: RE: [Xen-ia64-devel][Patch]Add two PAL calls which fix
>SMPwindowsinstallation crashing bug
>
>Hi Tristan, Alex, Wing,
>
>tgingold@xxxxxxx writes:
> > IMHO the Intel GFW can do all this work, there is no needs to do it in the
> > hypervisor.
>
>I read Tristan's GFW roughly.
>It seem to be already resolved in Tristan's GFW.
>
>The following is my understanding.
>
>GFW has a stub function SalBootRendezStub() beforehand.
> 1. GFW issues SAL_SET_VECTORS(SAL_VECTOR_OS_BOOT_RENDEZ, SalBootRendezStub)
>    in very early stage.
> 2. GOS(Guest OS) is invoked
>...[GOS running]
> 3. GOS issues SAL_SET_VECTORS(SAL_VECTOR_OS_BOOT_RENDEZ, guest_rendez)
> 4. GFW intercepts it. GFW just preserves the value of guest_rendez
>    in private data. (It never be propagated to XEN)
>...[GOS running]
> 5. GOS invokes a vcpu (sends IPI)
> 6. XEN jumps into SalBootRendezStub() instead of guest_rendez
> 7. GFW set cr.pta=15<<2
> 8. GFW jumps to guest_rendez "br.call.sptk.many b0=guest_rendez"
>...[GOS running]
> 9. GOS return to b0(SAL RETURN).
>10. GFW issues SAL_XEN_SAL_RETURN
>11. XEN stops the vcpu.
>
>I have two comments.
>In 7, I think initializing cr.pta should be XEN's job.
>In 10, I don't understand why the special SAL_XEN_SAL_RETURN is
>necessary instead of PAL_HALT. The difference is test_and_set_bit() or
>set_bit(). I think a vcpu with VCPU_down state never be at this point.
>Besides calling vcpu_sleep_no_sync() with VCPU_down state seems to be
>harmless.
>
>Thanks,
>Kouya

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