Messages in this thread | | | From | Vitaly Kuznetsov <> | Subject | Re: [Xen-devel] [PATCH linux v2 0/9] xen: pvhvm: support bootup on secondary vCPUs | Date | Mon, 25 Jul 2016 15:39:02 +0200 |
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Julien Grall <julien.grall@arm.com> writes:
> Hi David, > > On 25/07/16 13:38, David Vrabel wrote: >> On 30/06/16 16:56, 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. >> >> Applied to for-linus-4.8, thanks. > > It would have been nice to send a ping before applying. This patch > series is containing Xen ARM code which has not been acked by Stefano, > nor had feedback from ARM side. > > For instance given that all the hypercalls are representing a "vcpu > id" using "uint32_t" it is a bit weird to use "int" to define > xen_vcpu_id (see patch #3).
CPU id is usually 'int' in linux and now we pass it to all hypercalls as it is. It is a bit more convenient in the mapping I introduce as we can set it to a negative value to indicate there is no mapping available. I can definitely change that and use something like U32_MAX-1 to instead but I'm not sure it is worth it...
-- Vitaly
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