On 2013-02-19 16:20, Michael S. Tsirkin wrote: > apic overlaps PCI space. On real hardware it has > higher priority, emulate this correctly. > > This should addresses the following issue: > >> Subject: Re: [BUG] Guest OS hangs on boot when 64bit BAR present >> (kvm-apic-msi resource conflict) >> Sometime ago I reported an issue about guest OS hang when 64bit BAR present. >> http://lists.gnu.org/archive/html/qemu-devel/2012-01/msg03189.html >> http://lists.gnu.org/archive/html/qemu-devel/2012-12/msg00413.html >> >> Some more investigation has been done, so in this post I'll try to explain >> why it happens and offer possible solutions: >> >> *When the issue happens* >> The issue occurs on Linux guest OS if kernel version <2.6.36 >> A Guest OS hangs on boot when a 64bit PCI BAR is present in a system (if we >> use ivshmem driver for example) and occupies range within first >> 4 GB. >> >> *How to reproduce* >> I used the following qemu command to reproduce the case: >> /usr/local/bin/qemu-system-x86_64 -M pc-1.3 -enable-kvm -m 2000 -smp >> 1,sockets=1,cores=1,threads=1 -name Rh5332 -chardev >> socket,id=charmonitor,path=/var/lib/libvirt/qemu/Rh5332.monitor,server,nowait >> -mon chardev=charmonitor,id=monitor,mode=readline -rtc >> base=utc -boot cd -drive >> file=/home/akorolev/rh5332.img,if=none,id=drive-ide0-0-0,format=raw -device >> ide-drive,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0 -chardev >> file,id=charserial0,path=/home/akorolev/serial.log -device >> isa-serial,chardev=charserial0,id=serial0 -usb -vnc 127.0.0.1:0 -k en-us >> -vga cirrus -device ivshmem,shm,size=32M-device >> virtio-balloon-pci,id=balloon0 >> >> Tried different guests: Centos 5.8 64bit, RHEL 5.3 32bit, FC 12 64bit on all >> machines hang occurs in 100% cases >> >> *Why it happens* >> The issue basically comes from Linux PCI enumeration code. >> >> The OS enumerates 64BIT bars when device is enabled using the following >> procedure. >> 1. Write all FF's to lower half of 64bit BAR >> 2. Write address back to lower half of 64bit BAR >> 3. Write all FF's to higher half of 64bit BAR >> 4. Write address back to higher half of 64bit BAR >> >> For qemu it means that qemu pci_default_write_config() recevies all FFs for >> lower part of the 64bit BAR. >> Then it applies the mask and converts the value to "All FF's - size + 1" >> (FE000000 if size is 32MB). >> >> So for short period of time the range [0xFE000000 - 0xFFFFFFFF] will be >> occupied by ivshmem resource. >> For some reason it is lethal for further boot process. >> >> We have found that boot process screws up completely if kvm-apic-msi range >> is overlapped even for short period of time. (We still don't >> know why it happens, hope that the qemu maintainers can answer?) >> >> If we look at kvm-apic-msi memory region it is a non-overlapable memory >> region with hardcoded address range [0xFEE00000 - 0xFEF00000]. >> >> Here is a log we collected from render_memory_regions: >> >> system overlap 0 pri 0 [0x0 - 0x7fffffffffffffff] >> kvmvapic-rom overlap 1 pri 1000 [0xca000 - 0xcd000] >> pc.ram overlap 0 pri 0 [0xca000 - 0xcd000] >> ++ pc.ram [0xca000 - 0xcd000] is added to view >> .................... >> smram-region overlap 1 pri 1 [0xa0000 - 0xc0000] >> pci overlap 0 pri 0 [0xa0000 - 0xc0000] >> cirrus-lowmem-container overlap 1 pri 1 [0xa0000 - 0xc0000] >> cirrus-low-memory overlap 0 pri 0 [0xa0000 - 0xc0000] >> ++cirrus-low-memory [0xa0000 - 0xc0000] is added to view >> kvm-ioapic overlap 0 pri 0 [0xfec00000 - 0xfec01000] >> ++kvm-ioapic [0xfec00000 - 0xfec01000] is added to view >> pci-hole64 overlap 0 pri 0 [0x100000000 - 0x4000000100000000] >> pci overlap 0 pri 0 [0x100000000 - 0x4000000100000000] >> pci-hole overlap 0 pri 0 [0x7d000000 - 0x100000000] >> pci overlap 0 pri 0 [0x7d000000 - 0x100000000] >> ivshmem-bar2-container overlap 1 pri 1 [0xfe000000 - >> 0x100000000] >> ivshmem.bar2 overlap 0 pri 0 [0xfe000000 - 0x100000000] >> ++ivshmem.bar2 [0xfe000000 - 0xfec00000] is added to view >> ++ivshmem.bar2 [0xfec01000 - 0x100000000] is added to view >> ivshmem-mmio overlap 1 pri 1 [0xfebf1000 - 0xfebf1100] >> e1000-mmio overlap 1 pri 1 [0xfeba0000 - 0xfebc0000] >> cirrus-mmio overlap 1 pri 1 [0xfebf0000 - 0xfebf1000] >> cirrus-pci-bar0 overlap 1 pri 1 [0xfa000000 - 0xfc000000] >> vga.vram overlap 1 pri 1 [0xfa000000 - 0xfa800000] >> ++vga.vram [0xfa000000 - 0xfa800000] is added to view >> cirrus-bitblt-mmio overlap 0 pri 0 [0xfb000000 - 0xfb400000] >> ++cirrus-bitblt-mmio [0xfb000000 - 0xfb400000] is added to >> view >> cirrus-linear-io overlap 0 pri 0 [0xfa000000 - 0xfa800000] >> pc.bios overlap 0 pri 0 [0xfffe0000 - 0x100000000] >> ram-below-4g overlap 0 pri 0 [0x0 - 0x7d000000] >> pc.ram overlap 0 pri 0 [0x0 - 0x7d000000] >> ++pc.ram [0x0 - 0xa0000] is added to view >> ++pc.ram [0x100000 - 0x7d000000] is added to view >> kvm-apic-msi overlap 0 pri 0 [0xfee00000 - 0xfef00000] >> >> As you can see from log the kvm-apic-msi is enumarated last when range >> [0xfee00000 - 0xfef00000] is already occupied by ivshmem.bar2 >> [0xfec01000 - 0x100000000]. >> >> >> *Possible solutions* >> Solution 1. Probably the best would be adding the rule that regions which >> may not be overlapped are added to view first (In in other words >> regions which must not be overlapped have the highest priority). Please >> find patch in the following message. >> >> Solution 2. Raise priority of kvm-apic-msi resource. This is a bit >> misleading solution, as priority is only applicable for overlap-able >> regions, but this region must not be overlapped. >> >> Solution 3. Fix the issue at PCI level. Track if the resource is 64bit and >> apply changes if both parts of 64bit BAR are programmed. (It >> appears that real PCI bus controllers are smart enough to track 64bit BAR >> writes on PC, so qemu could do the same? Drawbacks are that >> tracking PCI writes is bit cumbersome, and such tracking may appear to >> somebody as a hack) > > --- > > The following patch is under test ATM. > Alexey, does it address the crash for you? > > > diff --git a/hw/pc.c b/hw/pc.c > index 53cc173..745c89d 100644 > --- a/hw/pc.c > +++ b/hw/pc.c > @@ -1154,7 +1154,8 @@ void ioapic_init_gsi(GSIState *gsi_state, const char > *parent_name) > } > qdev_init_nofail(dev); > d = SYS_BUS_DEVICE(dev); > - sysbus_mmio_map(d, 0, 0xfec00000); > + /* APIC overlaps the PCI window. */ > + sysbus_mmio_map_overlap(d, 0, 0xfec00000, 1000);
That's the IOAPIC, not the APIC. If you mean the IOAPIC, APIC and HPET would require higher prio, too. But I suppose this is really about the APIC and its special priority due to CPU-local access dispatching, right? Jan -- Siemens AG, Corporate Technology, CT RTC ITP SDP-DE Corporate Competence Center Embedded Linux
