On Tue, 2007-03-06 at 22:25 +0530, Mohan Kumar M wrote: > On Tue, Mar 06, 2007 at 03:16:55PM +0100, Michael Ellerman wrote: > > On Tue, 2007-03-06 at 19:27 +0530, Mohan Kumar M wrote: > > > Hi, > > > > > > Here comes the revised version of patch to fix the interrupt missing > > > problem when a kdump kernel is booted with "maxcpus=1" kernel parameter. > > > > > > In the xics initialization code a check is made to detemine whether > > > maxcpus kernel parameter is present and if its present then > > > default_distrib_server variable is initialized to the current boot cpu > > > id (by default_server variable). So that when ever a kernel is booted > > > with maxcpus kernel parameter all interrupts are routed to the boot cpu > > > only. > > > > > > Tested on POWER5 and JS20 systems. > > > > First, I don't know why we keep telling people to use maxcpus=1 for > > kexec/kdump - it's causing bugs, and I don't know of any that it fixes? > > Some distros want to use maxcpus=1 for kdump.
Yeah OK. > > Second, the way you've written this is not so good. The xics code should > > not be checking that "maxcpus" exists on the command line, it should be > > checking that the distrib server points to a cpu that is online - using > > cpu_online() etc. > > > > In get_irq_server function in xics.c, "noirqdistrib" command line > parameter is indirectly checked for routing the interrupts either to a > specific cpu or to all cpus. So I think checking for maxcpus= command > line parameter in xics.c is not a problem. No, it checks a flag, it doesn't run strstr on the saved command line. > Also during the xics_init_IRQ function other cpus (secondary cpus) will > not be online, they are made online at a later stage. So using > cpu_online() function at xics_init_IRQ will return true only for boot > cpu id. OK, so you should be able to use cpus possible map or something similar. cheers -- Michael Ellerman OzLabs, IBM Australia Development Lab wwweb: http://michael.ellerman.id.au phone: +61 2 6212 1183 (tie line 70 21183) We do not inherit the earth from our ancestors, we borrow it from our children. - S.M.A.R.T Person
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