Jerone Young
2005-Sep-13 20:33 UTC
[Xen-devel] Net grant tables breaking multiple nic domU
While working Bugzilla #183 I figured out what was the problem... Net grant tables...something that is marked as DANGEROUS in the kernel config...is on by default. When net grant tables is compiled in bringing up two interfaces in a domU crashes the domU kernel. But when I compile both Dom0 & DomU without net grant tables I am able to use two interfaces in domU with no problem. I don''t know a lot about net grant tables but could someone who know more about net grant tables take a look at this? -- Jerone Young IBM Linux Technology Center jyoung5@us.ibm.com 512-838-1157 (T/L: 678-1157) _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Nivedita Singhvi
2005-Sep-13 20:50 UTC
Re: [Xen-devel] Net grant tables breaking multiple nic domU
Jerone Young wrote:> While working Bugzilla #183 I figured out what was the problem... Net > grant tables...something that is marked as DANGEROUS in the kernel > config...is on by default. When net grant tables is compiled in bringing > up two interfaces in a domU crashes the domU kernel. But when I compile > both Dom0 & DomU without net grant tables I am able to use two > interfaces in domU with no problem. I don''t know a lot about net grant > tables but could someone who know more about net grant tables take a > look at this? > >Jerone, Did you not see Jim Dykman''s updates and posts on this bug? He''s found the root cause, and is putting together a patch, although some of it might be interim because it exposes another resource shortage which will have to be addressed somehow. Expect a patch from him in the next day or two, and see the bugzilla entry (and previous posts on xen-devel) from Jim for the details. thanks, Nivedita _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Jerone Young
2005-Sep-13 20:54 UTC
Re: [Xen-devel] Net grant tables breaking multiple nic domU
On Tue, 2005-09-13 at 13:50 -0700, Nivedita Singhvi wrote:> Jerone Young wrote: > > While working Bugzilla #183 I figured out what was the problem... Net > > grant tables...something that is marked as DANGEROUS in the kernel > > config...is on by default. When net grant tables is compiled in bringing > > up two interfaces in a domU crashes the domU kernel. But when I compile > > both Dom0 & DomU without net grant tables I am able to use two > > interfaces in domU with no problem. I don''t know a lot about net grant > > tables but could someone who know more about net grant tables take a > > look at this? > > > > > Jerone, > > Did you not see Jim Dykman''s updates and posts on this bug? > He''s found the root cause, and is putting together a patch, > although some of it might be interim because it exposes > another resource shortage which will have to be addressed > somehow. Expect a patch from him in the next day or two, > and see the bugzilla entry (and previous posts on xen-devel) > from Jim for the details.Yes I did see this. But if that is the case then why does disabling net grant tables fix the problem? So I just decided to come to the list to see if someone understanding the net grant table code might know.> > thanks, > Nivedita > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel >-- Jerone Young IBM Linux Technology Center jyoung5@us.ibm.com 512-838-1157 (T/L: 678-1157) _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Nivedita Singhvi
2005-Sep-13 21:04 UTC
Re: [Xen-devel] Net grant tables breaking multiple nic domU
Jerone Young wrote:>>Did you not see Jim Dykman''s updates and posts on this bug? >>He''s found the root cause, and is putting together a patch, >>although some of it might be interim because it exposes >>another resource shortage which will have to be addressed >>somehow. Expect a patch from him in the next day or two, >>and see the bugzilla entry (and previous posts on xen-devel) >>from Jim for the details. > > > Yes I did see this. But if that is the case then why does disabling net > grant tables fix the problem? So I just decided to come to the list to > see if someone understanding the net grant table code might know.The cause he identified is in the net grant code, so there is no conflict here, is there? When you disable the net grant code, it doesn''t use net grant tables, but falls back to the earlier code, which doesn''t have the bug. Yes, we could disable the net grant stuff, but as we discussed in previous threads on this list, that is a temporary workaround, and since this is the code we want to ship in 3.0, I see the correct thing to do is to find and fix the real problem, which Jim is doing. thanks, Nivedita _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Ian Pratt
2005-Sep-14 12:03 UTC
RE: [Xen-devel] Net grant tables breaking multiple nic domU
> The cause he identified is in the net grant code, so there is > no conflict here, is there? When you disable the net grant > code, it doesn''t use net grant tables, but falls back to the > earlier code, which doesn''t have the bug. Yes, we could > disable the net grant stuff, but as we discussed in previous > threads on this list, that is a temporary workaround, and > since this is the code we want to ship in 3.0, I see the > correct thing to do is to find and fix the real problem, > which Jim is doing.Yep, its just a case of dynamically allocating more grant table slots when an interface is brought up. The current BUG failure is needlessly severe. Ian _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel