linux-kernel - Re: [Xen-devel] [PATCH linux v3 0/9] xen: pvhvm: support bootup on secondary vCPUs

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Date:	Tue, 26 Jul 2016 10:36:47 -0700 (PDT)
From:	Stefano Stabellini <sstabellini@...nel.org>
To:	Vitaly Kuznetsov <vkuznets@...hat.com>
cc:	David Vrabel <david.vrabel@...rix.com>,
	xen-devel@...ts.xenproject.org, Juergen Gross <jgross@...e.com>,
	Stefano Stabellini <sstabellini@...nel.org>,
	Andrew Cooper <andrew.cooper3@...rix.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, Julien Grall <julien.grall@....com>,
	Ingo Molnar <mingo@...hat.com>,
	Jan Beulich <JBeulich@...e.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [Xen-devel] [PATCH linux v3 0/9] xen: pvhvm: support bootup on
 secondary vCPUs

On Tue, 26 Jul 2016, Vitaly Kuznetsov wrote:
> David Vrabel <david.vrabel@...rix.com> writes:
> 
> > On 26/07/16 13:30, Vitaly Kuznetsov wrote:
> >> 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 v2:
> >> - Use 'uint32_t' for xen_vcpu_id mapping [Julien Grall]
> >> - Rebased to linux-4.7
> >
> > I already applied v2.  If you provide an incremental patch I can queue
> > it for 4.9.
> 
> Ok,
> 
> in that case we can wait till the real mapping is done for ARM to change
> the type of xen_vcpu_id I guess.

It would still be nice to make the change. Please send it as an
incremental patch. It is OK if it is queued for 4.9.