From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: [PATCH v7 2/5] sysctl: Add sysctl interface for querying PCI topology Date: Tue, 21 Apr 2015 14:30:00 +0100 Message-ID: <553650D8.2070802@citrix.com> References: <1429289966-4121-1-git-send-email-boris.ostrovsky@oracle.com> <1429289966-4121-3-git-send-email-boris.ostrovsky@oracle.com> <553611EC0200007800074107@mail.emea.novell.com> <55364905.6030900@oracle.com> <55364D38.3020203@citrix.com> <55364CE5.4050602@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <55364CE5.4050602@oracle.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Boris Ostrovsky , Jan Beulich Cc: elena.ufimtseva@oracle.com, wei.liu2@citrix.com, ian.campbell@citrix.com, stefano.stabellini@eu.citrix.com, dario.faggioli@citrix.com, ian.jackson@eu.citrix.com, xen-devel@lists.xen.org, keir@xen.org, dgdegra@tycho.nsa.gov List-Id: xen-devel@lists.xenproject.org On 21/04/15 14:13, Boris Ostrovsky wrote: > > On 04/21/2015 09:14 AM, Andrew Cooper wrote: >> On 21/04/15 13:56, Boris Ostrovsky wrote: >>> On 04/21/2015 03:01 AM, Jan Beulich wrote: >>>>>>> --- a/docs/misc/xsm-flask.txt >>>>>>> +++ b/docs/misc/xsm-flask.txt >>>>>>> @@ -121,6 +121,7 @@ __HYPERVISOR_sysctl >>>>>>> (xen/include/public/sysctl.h) >>>>>>> * XEN_SYSCTL_cpupool_op >>>>>>> * XEN_SYSCTL_scheduler_op >>>>>>> * XEN_SYSCTL_coverage_op >>>>>>> + * XEN_SYSCTL_pcitopoinfo >>>> No additions to this list are permitted. Either the new sub-op is >>>> disaggregation safe (which it looks to be), or it can't be accepted. >>> True, it *is* safe, but why then cputopoinfo and numainfo are in this >>> list? They look to be safe as well. >> This list includes "not yet audited". It is quite likely that some >> entries in the list are safe. >> >> fwiw, neither cputopo nor numainfo are currently safe for very large >> systems. > > Why would safety of an operation depend on system size? And how are > these two unsafe? (Because maybe then PCI topology query is unsafe in > the same manner) PCI topology has continuations in it. cpu/numa info is bounded by host values, but does attempt to cover all cpus/nodes in a single pass, which will get progressively longer as the server gets larger. ~Andrew