On 29/05/15 07:24, Jason Fritcher wrote: > On Wed, 20 May 2015, Major Hayden wrote: > > >/ On 05/20/2015 05:41 AM, Jan Beulich wrote:/ > >/ > Considering that no-one else is seeing this - is this perhaps connected/ > >/ > to you building Xen with pre-release gcc 5.0.1? This is also because in/ > >/ > order for the above to indeed occur, mmio_ro_do_page_fault()'s/ > >/ > put_page() would need to drop the last reference of a page, yet/ > >/ > page_get_owner_and_reference() doesn't obtain a reference when/ > >/ > a page is unallocated (and hence unowned), i.e. normally a page/ > >/ > would have a refcount of at least 2 here. Hence this would be/ > >/ > possible only due to a race, but the exact same race to be observed/ > >/ > on different hardware _and_ under an emulator is extremely unlikely./ > > You could try with the xen.gz file from > https://copr-be.cloud.fedoraproject.org/results/myoung/xentest/fedora-21-x86_64/xen-4.5.1-0.rc1.fc21/xen-hypervisor-4.5.1-0.rc1.fc21.x86_64.rpm > It is roughly the same version of xen but built against Fedora 21 and gcc > 4.9.2. If that works then it probably is gcc 5. > Greetings, > > I have run into pretty much the same issue as the original poster. > > I am running a recently updated Arch Linux system, with GCC 5.1.0, > using UEFI and gummiboot to boot. I currently have a build of Xen > 4.4.1, built with GCC 4.9.2 from before my last update, that is > functioning correctly on this machine. But the builds of Xen 4.5.0, > using GCC 5 and mingw64-binutils for the EFI binary, are all failing > when Xen starts the Linux kernel, with the same error mentioned in the > subject. Below is the boot log I captured via the serial port. > > http://pastebin.com/bBC78306 > > Wondering if my specific toolchain was the issue, I downloaded the > Fedora 22 version of xen-hypervisor and installed its EFI Xen binary > over my compiled binary and received an identical error message, with > slightly different addresses in the panic dump. The Fedora version was > compiled with GCC 5.0.1. Below is the boot log I captured from that > binary. > > http://pastebin.com/jvg1JazC > > After finding this thread, and specifically, the quoted message above, > I downloaded that xen-hypervisor package and installed its EFI Xen > binary. That binary boots successfully, as seen by the captured boot > log below. > > http://pastebin.com/DKxwaU2U > > So, while I’m not familiar enough with Xen to begin to have an idea of > what could possibly be wrong with Xen or GCC 5 to be causing this bug, > I’d like to do what I can to track down the issue so I can get a > working build of Xen 4.5. :)
Are you in a position to compile identical Xen 4.5 source with two different versions of gcc? (current staging-4.5 staging even has the gcc5 build fix in) If it is a gcc compiler bug, we would expect the version compiled with gcc 4.9 to work fine, but the one compiled with 5 to fail in the identified manor. ~Andrew
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