Jan Kiszka wrote: > Jan Kiszka wrote: >> Jan Kiszka wrote: >>> Avi Kivity wrote: >>>> Jan Kiszka wrote: >>>>> [ taking Sheng's comments into account ] >>>>> >>>>> The logic of kvm_apic_accept_pic_intr has a minor, practically hardly >>>>> relevant incorrectness: PIC interrupts are still delivered even if the >>>>> APIC of VPU0 (BSP) is disabled. This does not comply with the Virtual >>>>> Wire mode according to the Intel MP spec. >>>>> >>>> This breaks Windows XP with the Standard PC HAL, so I am unapplying this >>>> patch. >>> Hmm, this points to either an APIC setup or BIOS bug. To my >>> understanding, the Standard PC HAL should not fiddle with the APIC, so >>> what the BIOS leaves behind should counts. But I think I found no traces >>> of APIC manipulation in rombios32.c. >> Manipulation on UP systems. There is fiddling for SMP. But I will check >> again. > > I take everything back: For yet unknown reasons Windows' standard HAL > actually decides to disable the APIC actively. Either there is a > short-path around a disabled APIC for Virtual Wire mode in Real Live > (though I fail to read this out of the spec), or Windows simply has a > bug here (MS insists on NOT supporting the Standard HAL on APIC systems > [1] - precisely the setup KVM is providing). Sheng, any comments on > this? Guess we have to live with the previous version, maybe with some > refactoring + commenting.
I was curious and played with my corresponding qemu patch [1]: It works with the same Windows image that hangs under KVM. Then I looked at a prominent guest-visible difference: the reported CPU type. QEMU claims to provide a CPU called "qemu64" by default. Changing this to Pentium2 or newer makes Windows issue the lethal APIC disable command. On the other hand, calling kvm with "-cpu pentium" makes Windows boot again. However, I still can't tell from this if we see a Windows bug or if the change is incorrect (but me feeling tends to the former). Jan [1] http://permalink.gmane.org/gmane.comp.emulators.qemu/31429
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