Eduardo Habkost wrote: > On Thu, Nov 20, 2008 at 12:22:53PM -0200, Eduardo Habkost wrote: >> Hi, >> >> When using a kvm.git kernel as host, I am getting guest boot failures >> when booting Fedora Rawhide kernel (2.6.27.5-117.fc10.x86_64). Guest >> stops booting at: >> >> ENABLING IO-APIC IRQs >> ..TIMER: vector=0x30 apic1=0 pin1=0 apic2=-1 pin2=-1 >> ..MP-BIOS bug: 8254 timer not connected to IO-APIC >> ...trying to set up timer (IRQ0) through the 8259A ... >> ..... (found apic 0 pin 0) ... >> ....... failed. >> ...trying to set up timer as Virtual Wire IRQ... >> ..... failed. >> ...trying to set up timer as ExtINT IRQ... > > I've just found out this problem happens because the guest has HZ=1000 > and the host had HZ=250 and no CONFIG_HIGH_RES_TIMERS. > > With this setup, the host is not managing to inject enough timer > interrupts during the mdelay() loop on timer_irq_works(). >
Interesting, and plausible. My observation so far is a sporadic test failure, often correlating with some raised host OS load. I'm running a high-res kernel, but that cannot prevent that this only 10 ticks long loop of the guest may obtain too few CPU cycles to handle enough of them once in a while (IIRC, it needs 4 out of the 10 ticks to declare the timer routing functional). Maybe Gleb's anti-coalesce patches for the PIC can also deal with your timer resolution conflict. At least worth a try... Jan
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