Hi Boris, On 12/11/2018 10:50 AM, Borislav Petkov wrote: > On Tue, Dec 11, 2018 at 10:33:59AM -0800, Reinette Chatre wrote: >> I am not sure that this is an issue when updating a schemata in the >> general case. In the case when just CAT schemata (without >> pseudo-locking) is updated then the cpu mask associated with the cache >> instance is indeed used to determine which CPUs should have their >> registers changed but only the current CPU is not checked for being >> online, for the other CPUs smp_call_function_many() is used that >> includes an online check. > > Well, in your fix rdtgroup_schemata_write() disables hotplug for its > whole duration and doesn't look at what schemata update is being done, > right? Correct. I just wanted to emphasize that it is not the schemata writing that needs to be protected, but instead the pseudo-locking code that runs after schemata programming that needs to run on a particular CPU. The new patch subject could be interpreted to mean the former ... but that is starting to sound like nitpicking by me. >> I had the same question in V1's notes to the maintainer :) > > Whoops, and I read that... Sorry. :-\ Not a problem at all :) >> My initial concern was the lack of IS_ERR checking. Understanding the >> flow better now it seems to me that this is indeed not a bug now. The >> reasoning is that an ERR_PTR is only returned when a negative id is >> provided in the parameters to rdt_find_domain(). There are currently >> only two places where a negative id could be provided to >> rdt_find_domain(), domain_add_cpu() and domain_remove_cpu(), and both >> locations test the return value using IS_ERR. > > Right. I'll queue it for the normal merge window. Thank you very much. Reinette
