On 08/29/2011 01:14 AM, Kevin O'Connor wrote:
On Sun, Aug 28, 2011 at 10:42:49PM +0200, Jan Kiszka wrote: > On 2011-08-28 20:54, Alexander Graf wrote: > > > > On 28.08.2011, at 02:42, Avi Kivity wrote: > > > >> On 08/26/2011 08:32 AM, ya su wrote: > >>> hi,Avi: > >>> > >>> I met the same problem, tons of hpet vm_exits(vector 209, fault > >>> address is in the guest vm's hpet mmio range), even I disable hpet > >>> device in win7 guest vm, it still produce a larget amount of vm_exits > >>> when trace-cmd ; I add -no-hpet to start the vm, it still has HPET > >>> device inside VM. > >>> > >>> Does that means the HPET device in VM does not depend on the > >>> emulated hpet device in qemu-kvm? Is there any way to disable the VM > >>> HPET device to prevent so many vm_exits? Thansk. > >>> > >> > >> Looks like a bug to me. > > > > IIRC disabling the HPET device doesn't remove the entry from the DSDT, no? So the guest OS might still think it's there while nothing responds (read returns -1). > > Exactly. We have a fw_cfg interface in place for quite a while now > (though I wonder how the firmware is supposed to tell -no-hpet apart > from QEMU versions that don't provide this data - both return count = > 255), but SeaBios still exposes one HPET block at a hard-coded address > unconditionally. > > There was quite some discussion about the corresponding Seabios patches > back then but apparently no consensus was found. Re-reading it, I think > Kevin asked for passing the necessary DSDT fragments from QEMU to the > firmware instead of using a new, proprietary fw_cfg format. Is that > still the key requirement for any patch finally fixing this bug? My preference would be to use the existing ACPI table passing interface (fw_cfg slot 0x8000) to pass different ACPI tables to SeaBIOS. SeaBIOS doesn't currently allow that interface to override tables SeaBIOS builds itself, but it's a simple change to rectify that. When this was last proposed, it was raised that the header information in the ACPI table may then not match the tables that SeaBIOS builds. I think I proposed at that time that SeaBIOS could use the header of the first fw_cfg table (or some other fw_cfg interface) to populate the headers of its table headers. However, there was no consensus. Note - the above is in regard to the HPET table. If the HPET entry in the DSDT needs to be removed then that's a bigger change.
Can't seabios just poke at the hpet itself and see if it exists or not? -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
