On 04/09/18 20:35, Julien Grall wrote: > Hi, > > On 09/04/2018 08:21 PM, Julien Grall wrote: >> A follow-up patch will require to know the number of vCPUs when >> initializating the vGICv3 domain structure. However this information is >> not available at domain creation. This is only known once >> XEN_DOMCTL_max_vpus is called for that domain. >> >> In order to get the max vCPUs around, delay the domain part of the vGIC >> v3 initialization until the first vCPU of the domain is initialized. >> >> Signed-off-by: Julien Grall <julien.gr...@arm.com> >> >> --- >> >> Cc: Andrew Cooper <andrew.coop...@citrix.com> >> >> This is nasty but I can't find a better way for Xen 4.11 and older. This >> is not necessary for unstable as the number of vCPUs is known at domain >> creation. >> >> Andrew, I have CCed you to know whether you have a better idea where to >> place this call on Xen 4.11 and older. > > I just noticed that d->max_vcpus is initialized after > arch_domain_create. So without this patch on Xen 4.12, it will not work. > > This is getting nastier because arch_domain_init is the one initialize > the value returned by dom0_max_vcpus. So I am not entirely sure what > to do here.
The positioning after arch_domain_create() is unfortunate, but I couldn’t manage better with ARM's current behaviour and Jan's insistence that the allocation of d->vcpu was common. I'd prefer if the dependency could be broken and the allocation moved earlier. One option might be to have an arch_check_domainconfig() (or similar?) which is called very early on and can sanity check the values, including cross-checking the vgic and max_vcpus settings? It could even be responsible for mutating XEN_DOMCTL_CONFIG_GIC_NATIVE into the correct real value. As for your patch here, its a gross hack, but its probably the best which can be done. I have to admit that I'm surprised/concerned that Xen has lasted this long with such a fundamental gap in domain creation. ~Andrew _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
