Re: [Xen-devel] [PATCH 8/8] xen/pvh: Enable CPU hotplug

From	Andrew Cooper <andrew.cooper3@citrix.com>
Newsgroups	linux.kernel
Subject	Re: [Xen-devel] [PATCH 8/8] xen/pvh: Enable CPU hotplug
Date	2016-10-27 17:10 +0200
Message-ID	<swUtA-3yF-17@gated-at.bofh.it> (permalink)
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On 27/10/16 15:25, Boris Ostrovsky wrote:
>
>
> On 10/14/2016 03:01 PM, Boris Ostrovsky wrote:
>> On 10/14/2016 02:41 PM, Andrew Cooper wrote:
>>> On 14/10/16 19:05, Boris Ostrovsky wrote:
>>>> PVH guests don't receive ACPI hotplug interrupts and therefore
>>>> need to monitor xenstore for CPU hotplug event.
>>> Why not?  If they don't, they should.  As we are providing ACPI anyway,
>>> we should provide all bits of it.
>>
>> We don't have IOAPIC, which is how these interrupts are typically
>> delivered. I suppose we might be able to specify it as something else.
>>
>> I'll look into this.
>
>
> (+Jan)
>
> Yes, we can do this. The main issue is how to deal with event
> registers (i.e FADT.x_pm1a_evt_blk) and AML's PRST region (which
> specifies online CPU map).
>
> Currently these are accessed via IO space and are handled by qemu.
>
> There are a couple of ways to deal with this that I can see.
>
> 1. We can implement ioreq handling in the hypervisor, there are only a
> few addresses that need handling.
>
> 2. We can implement those registers in memory space and have libxl
> update them them on a hotplug command. This appears to be possible
> because these registers mostly just consume writes without side
> effects so they can be simple memory locations. The one exception is
> updating status bits (they are cleared by writing 1s) but I think we
> can do this from the AML.
>
> Other than that the only other thing is setting up an event channel
> between the toolstack and the guest (either via xenstore or perhaps by
> having a reserved port for SCI).
>
> I have a prototype with (2) (except for the bit clearing part) but I
> want to hear comments on this approach before I write proper patches.

Xen already deals with 1 for HVM guests.  We should do the same for PVH
guests as well.

-1 to anything involving looping a PVH dom0 back around to some entity
running inside dom0.

~Andrew

~Andrew

Thread

[PATCH 0/8] PVH v2 support Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-10-14 20:20 +0200
  [PATCH 7/8] xen/pvh: PVH guests always have PV devices Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-10-14 20:20 +0200
    Re: [Xen-devel] [PATCH 7/8] xen/pvh: PVH guests always have PV  devices Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> - 2016-10-14 21:30 +0200
    Re: [PATCH 7/8] xen/pvh: PVH guests always have PV devices Juergen Gross <jgross@suse.com> - 2016-10-18 18:00 +0200
  [PATCH 5/8] xen/pvh: Prevent PVH guests from using PIC, RTC and IOAPIC Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-10-14 20:20 +0200
    Re: [Xen-devel] [PATCH 5/8] xen/pvh: Prevent PVH guests from using  PIC, RTC and IOAPIC Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> - 2016-10-14 21:20 +0200
      Re: [Xen-devel] [PATCH 5/8] xen/pvh: Prevent PVH guests from using  PIC, RTC and IOAPIC Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-10-14 21:40 +0200
    Re: [PATCH 5/8] xen/pvh: Prevent PVH guests from using PIC, RTC and  IOAPIC Roger Pau Monné <roger.pau@citrix.com> - 2016-10-26 12:50 +0200
      Re: [PATCH 5/8] xen/pvh: Prevent PVH guests from using PIC, RTC and  IOAPIC Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-10-26 16:50 +0200
        Re: [PATCH 5/8] xen/pvh: Prevent PVH guests from using PIC, RTC and  IOAPIC Roger Pau Monné <roger.pau@citrix.com> - 2016-10-26 17:20 +0200
          Re: [PATCH 5/8] xen/pvh: Prevent PVH guests from using PIC, RTC and  IOAPIC Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-10-26 18:10 +0200
  [PATCH 8/8] xen/pvh: Enable CPU hotplug Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-10-14 20:20 +0200
    Re: [Xen-devel] [PATCH 8/8] xen/pvh: Enable CPU hotplug Andrew Cooper <andrew.cooper3@citrix.com> - 2016-10-14 20:50 +0200
      Re: [Xen-devel] [PATCH 8/8] xen/pvh: Enable CPU hotplug Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-10-14 21:10 +0200
        Re: [Xen-devel] [PATCH 8/8] xen/pvh: Enable CPU hotplug Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-10-27 16:30 +0200
          Re: [Xen-devel] [PATCH 8/8] xen/pvh: Enable CPU hotplug Andrew Cooper <andrew.cooper3@citrix.com> - 2016-10-27 17:10 +0200
            Re: [Xen-devel] [PATCH 8/8] xen/pvh: Enable CPU hotplug Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-10-27 18:30 +0200
  [PATCH 4/8] xen/pvh: Bootstrap PVH guest Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-10-14 20:20 +0200
    Re: [Xen-devel] [PATCH 4/8] xen/pvh: Bootstrap PVH guest Andrew Cooper <andrew.cooper3@citrix.com> - 2016-10-14 20:50 +0200
      Re: [Xen-devel] [PATCH 4/8] xen/pvh: Bootstrap PVH guest Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-10-14 21:00 +0200
        Re: [Xen-devel] [PATCH 4/8] xen/pvh: Bootstrap PVH guest Andrew Cooper <andrew.cooper3@citrix.com> - 2016-10-14 21:20 +0200
    Re: [Xen-devel] [PATCH 4/8] xen/pvh: Bootstrap PVH guest Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> - 2016-10-14 21:20 +0200
      Re: [Xen-devel] [PATCH 4/8] xen/pvh: Bootstrap PVH guest Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-10-14 21:40 +0200
  [PATCH 2/8] x86/head: Refactor 32-bit pgtable setup Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-10-14 20:20 +0200
    Re: [PATCH 2/8] x86/head: Refactor 32-bit pgtable setup hpa@zytor.com - 2016-10-14 20:40 +0200
      Re: [PATCH 2/8] x86/head: Refactor 32-bit pgtable setup Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-10-14 20:50 +0200
        Re: [PATCH 2/8] x86/head: Refactor 32-bit pgtable setup hpa@zytor.com - 2016-10-14 21:10 +0200
          Re: [PATCH 2/8] x86/head: Refactor 32-bit pgtable setup Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-10-14 21:30 +0200
    Re: [PATCH 2/8] x86/head: Refactor 32-bit pgtable setup Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-10-31 13:40 +0100
  [PATCH 3/8] xen/pvh: Import PVH-related Xen public interfaces Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-10-14 20:20 +0200
    Re: [Xen-devel] [PATCH 3/8] xen/pvh: Import PVH-related Xen public  interfaces Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> - 2016-10-14 20:40 +0200
    Re: [PATCH 3/8] xen/pvh: Import PVH-related Xen public interfaces Juergen Gross <jgross@suse.com> - 2016-10-21 13:00 +0200
  [PATCH 1/8] xen/x86: Remove PVH support Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-10-14 20:20 +0200
    Re: [Xen-devel] [PATCH 1/8] xen/x86: Remove PVH support Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> - 2016-10-14 20:40 +0200
    Re: [PATCH 1/8] xen/x86: Remove PVH support Juergen Gross <jgross@suse.com> - 2016-10-18 15:50 +0200
      Re: [PATCH 1/8] xen/x86: Remove PVH support Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-10-18 16:50 +0200
        Re: [PATCH 1/8] xen/x86: Remove PVH support Juergen Gross <jgross@suse.com> - 2016-10-18 17:40 +0200
          Re: [PATCH 1/8] xen/x86: Remove PVH support Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-10-18 17:50 +0200

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