linux-kernel - Re: [PATCH linux v2 0/9] xen: pvhvm: support bootup on secondary vCPUs

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Message-ID: <87vazuvzyt.fsf@vitty.brq.redhat.com>
Date:	Mon, 25 Jul 2016 11:17:30 +0200
From:	Vitaly Kuznetsov <vkuznets@...hat.com>
To:	David Vrabel <david.vrabel@...rix.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc:	linux-kernel@...r.kernel.org, x86@...nel.org,
	Stefano Stabellini <sstabellini@...nel.org>,
	xen-devel@...ts.xenproject.org, Juergen Gross <jgross@...e.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Jan Beulich" <JBeulich@...e.com>,
	Andrew Cooper <andrew.cooper3@...rix.com>
Subject: Re: [PATCH linux v2 0/9] xen: pvhvm: support bootup on secondary vCPUs

Vitaly Kuznetsov <vkuznets@...hat.com> writes:

> It may happen that Xen's and Linux's ideas of vCPU id diverge. In
> particular, when we crash on a secondary vCPU we may want to do kdump
> and unlike plain kexec where we do migrate_to_reboot_cpu() we try booting
> on the vCPU which crashed. This doesn't work very well for PVHVM guests as
> we have a number of hypercalls where we pass vCPU id as a parameter. These
> hypercalls either fail or do something unexpected. To solve the issue we
> need to have a mapping between Linux's and Xen's vCPU ids.
>
> This series solves the issue for x86 PVHVM guests. PV guests don't (and
> probably won't) support kdump so I always assume Xen's vCPU id == Linux's
> vCPU id. ARM guests will probably need to get proper mapping once we start
> supporting kexec/kdump there.
>
> Changes since v1:
> - "x86/acpi: store ACPI ids from MADT for future usage" patch added.
> - Use ACPI ids instead of vLAPIC ids/2 [Andrew Cooper, Jan Beulich]
> - Introduce xen_vcpu_nr() helper [David Vrabel].
> - Modify all callers of HYPERVISOR_vcpu_op() instead of modifying
>   HYPERVISOR_vcpu_op() [David Vrabel]

David, Boris,

I didn't get any feedback for the v2 of this patchset, is it ready to go
in for 4.8 or is there anything else I need to do to make this happen?

BTW, the patch describing the de facto "ACPI id == Xen's VCPU id" policy
is in xen.git:

commit ea210c52abb6458e39f5365f7f2c3abb9c191c47
Author: Vitaly Kuznetsov <vkuznets@...hat.com>
Date:   Tue Jul 12 13:44:42 2016 +0200

    x86, hvm: document the de facto policy for vCPU ids

Thanks,

-- 
  Vitaly