Here is my patch so far. There were a few things wrong, although I didn't really keep notes. The limits were mixed up, the long mode bit was set on all descriptors when it's only valid for the code segment, privilege level 0 is the OS and 3 is for applications and not the other way around, and I think the type was being set wrong for one of the segments. Also, the syscall and sysenter registers (star and friends) require the segments in the GDT to be in a particular order which I don't think they were.
Gabe On Tue, Dec 9, 2014 at 4:22 PM, Dutu, Alexandru via gem5-dev < gem5-dev@gem5.org> wrote: > So, I am doing this on an AMD system and I have SE working and am able to > get FS entering into virtualized mode. However, in FS I get an early > exception while the kernel is booting. This seems a bit different from what > Nilay and Adrian observed for FS. Could you please share the diffs that got > FS working? > > Thanks, > Alex > > -----Original Message----- > From: gem5-dev [mailto:gem5-dev-boun...@gem5.org] On Behalf Of Gabe Black > via gem5-dev > Sent: Tuesday, December 09, 2014 6:07 PM > To: gem5 Developer List > Subject: Re: [gem5-dev] x86 SE kvm functionality (AMD vs Intel) > > Oh, I see you have FS working again and not SE. NM, I'll keep looking. > > Gabe > > On Tue, Dec 9, 2014 at 4:04 PM, Gabe Black <gabebl...@google.com> wrote: > > > I have FS working again which is good, but I'm still having problems > > with SE. If you could let me know what you did to get things going > > that would be very helpful. > > > > Gabe > > > > On Tue, Dec 9, 2014 at 10:06 AM, Dutu, Alexandru via gem5-dev < > > gem5-dev@gem5.org> wrote: > > > >> Hi Adrian, > >> > >> Sorry for missing your first email. I do see the interchanged segment > >> limits for full system mode, though I get a different behaviour on my > >> system. The simulation seems to hang in the following manner: > >> > >> Processor #0 (Bootup-CPU) > >> I/O APIC #1 at 0xFEC00000. > >> Setting APIC routing to flat > >> Processors: 1 > >> PANIC: early exception rip ffffffff807909a9 error 9 cr2 > >> ffffffffff5fd020 > >> > >> Can please provide a patch with all the modifications that fixed the > >> issue on your system? > >> > >> Thank you, > >> Alex > >> ________________________________________ > >> From: gem5-dev [gem5-dev-boun...@gem5.org] on behalf of Adrián Colaso > >> Diego via gem5-dev [gem5-dev@gem5.org] > >> Sent: Tuesday, December 09, 2014 2:09 AM > >> To: gem5 Developer List > >> Subject: Re: [gem5-dev] x86 SE kvm functionality (AMD vs Intel) > >> > >> You are right Nilay. I sent an email last week but nobody has replied. > >> > >> It seems that descriptors (cdDesc, dsDesc and tssDesc) located in > >> src/arch/x86/system.cc file are not well-initialized and as a > >> consequence kvm does not work when running in full-system mode. > >> > >> Segment limits values (limitHigh and limitLow) are interchanged and > >> several segment descriptor values are wrong too. If these values are > >> corrected kvm works again as before. > >> > >> Adrian > >> > >> El lun, 08-12-2014 a las 22:50 -0600, Nilay Vaish via gem5-dev escribió: > >> > I also faced problem in getting KVM CPU to run in FS mode. I > >> > figured > >> that > >> > the following changeset causes problems: > >> > > >> > author Alexandru Dutu <alexandru.d...@amd.com> > >> > Sun Nov 23 18:01:08 2014 -0800 (2 weeks ago) > >> > changeset 10554 fe2e2f06a7c8 > >> > > >> > I saw the hardware reason 0x80000021, but did not try to figure > >> > what was going on wrong. > >> > > >> > -- > >> > Nilay > >> > > >> > On Mon, 8 Dec 2014, Gabe Black via gem5-dev wrote: > >> > > >> > > I'm pretty sure entering 64 bit mode is the same between AMD and > >> > > Intel CPUs. I vaguely remember there being some subtle page table > >> > > difference though, and gem5 is building the page tables in SE > >> > > mode instead of the kernel. > >> > > > >> > > Gabe > >> > > > >> > > On Mon, Dec 8, 2014 at 7:44 PM, Dutu, Alexandru via gem5-dev < > >> > > gem5-dev@gem5.org> wrote: > >> > > > >> > >> Hi Mike, > >> > >> > >> > >> trace-cmd is a very handy tool to get an overview of what the > >> > >> kvm > >> kernel > >> > >> module is doing before going into gdb. In extreme cases ftrace > >> > >> can be useful as well. > >> > >> What is the error that you are seeing? Is it still failing to > >> > >> enter virtualized mode? > >> > >> > >> > >> If that is the case and the hardware reason is 0x80000021, that > >> seems to > >> > >> be an unrecoverable exception (drivers/hv/hyperv_vmbus.h in > >> > >> linux > >> kernel > >> > >> source code). When running in SE mode, we are trying to bring > >> > >> the > >> machine > >> > >> state to full 64bit mode without going through legacy modes. It > >> might be > >> > >> that Intel machines have a different way of going to 64bit mode > >> > >> than > >> AMD > >> > >> machines (different CR4, different way of enabling 64bit mode > >> > >> page > >> tables > >> > >> etc.). I remember dealing with these issue for AMD platforms by > >> > >> going through System Programming manual and making sure gem5 > >> > >> gets all the > >> bits > >> > >> right as there is not much the KVM kernel model will tell about > >> > >> the > >> cause > >> > >> of failure. > >> > >> > >> > >> Best regards, > >> > >> Alex > >> > >> ________________________________________ > >> > >> From: gem5-dev [gem5-dev-boun...@gem5.org] on behalf of Gabe > >> > >> Black > >> via > >> > >> gem5-dev [gem5-dev@gem5.org] > >> > >> Sent: Monday, December 08, 2014 7:08 PM > >> > >> To: gem5 Developer List > >> > >> Subject: Re: [gem5-dev] x86 SE kvm functionality (AMD vs Intel) > >> > >> > >> > >> I'm not an expert either, but I did have problems running KVM in > >> > >> SE > >> mode on > >> > >> an Intel CPU. I didn't look into it that much, but I think > >> > >> things > >> failed in > >> > >> the kernel somewhere. What might be happening is that the > >> > >> different > >> vendors > >> > >> hardware virtualization mechanisms are more or less picky about > >> various > >> > >> things. Something might be set up incorrectly, and one > >> implementation gets > >> > >> more upset about it than the other. I believe there are tools > >> > >> which > >> will > >> > >> help you determine whether your VM state is legal. Perhaps > >> > >> Andreas > >> can tell > >> > >> you more about those? > >> > >> > >> > >> Gabe > >> > >> > >> > >> On Mon, Dec 8, 2014 at 4:29 PM, mike upton via gem5-dev < > >> gem5-dev@gem5.org > >> > >>> > >> > >> wrote: > >> > >> > >> > >>> I have verified that x86 kvm works fine on AMD platforms, but > >> > >>> fails > >> on > >> > >>> Intel platforms. > >> > >>> > >> > >>> Any hints about how to narrow down the cause (other than diving > >> into gdb, > >> > >>> which I will do). > >> > >>> > >> > >>> I am not an expert in KVM or how gem5 hooks up to libkvm. > >> > >>> _______________________________________________ > >> > >>> gem5-dev mailing list > >> > >>> gem5-dev@gem5.org > >> > >>> http://m5sim.org/mailman/listinfo/gem5-dev > >> > >>> > >> > >> _______________________________________________ > >> > >> gem5-dev mailing list > >> > >> gem5-dev@gem5.org > >> > >> http://m5sim.org/mailman/listinfo/gem5-dev > >> > >> _______________________________________________ > >> > >> gem5-dev mailing list > >> > >> gem5-dev@gem5.org > >> > >> http://m5sim.org/mailman/listinfo/gem5-dev > >> > >> > >> > > _______________________________________________ > >> > > gem5-dev mailing list > >> > > gem5-dev@gem5.org > >> > > http://m5sim.org/mailman/listinfo/gem5-dev > >> > > > >> > _______________________________________________ > >> > gem5-dev mailing list > >> > gem5-dev@gem5.org > >> > http://m5sim.org/mailman/listinfo/gem5-dev > >> > >> > >> _______________________________________________ > >> gem5-dev mailing list > >> gem5-dev@gem5.org > >> http://m5sim.org/mailman/listinfo/gem5-dev > >> _______________________________________________ > >> gem5-dev mailing list > >> gem5-dev@gem5.org > >> http://m5sim.org/mailman/listinfo/gem5-dev > >> > > > > > _______________________________________________ > gem5-dev mailing list > gem5-dev@gem5.org > http://m5sim.org/mailman/listinfo/gem5-dev > _______________________________________________ > gem5-dev mailing list > gem5-dev@gem5.org > http://m5sim.org/mailman/listinfo/gem5-dev > _______________________________________________ gem5-dev mailing list gem5-dev@gem5.org http://m5sim.org/mailman/listinfo/gem5-dev
