On Tue, Feb 07, 2012 at 04:57:41PM -0500, Don Zickus wrote: > On Thu, Feb 02, 2012 at 03:24:46PM -0800, Eric W. Biederman wrote: > > > Eric, brought up a point that because the boot code was restructured we may > > > not need to disable the io apic any more in the crash path. The original > > > concern that led to the development of disable_IO_APIC, was that the TSC > > > calibration on boot up relied on the PIT timer for reference. Access > > > to the PIT required 8259 interrupts to be working. This wouldn't work > > > if the ioapic needed to be configured. So on panic path, the ioapic was > > > reconfigured to use virtual wire mode to allow the 8259 to passthrough. > > > > A small clarification originally it was the jiffies calibration that > > would fail if we could cause the PIT to generate interrupts through the > > 8259. The boot would then hang at calibrating jiffies. > > Ok. Thanks! So now what has changed? Do we setup LAPIC and IOAPIC early enough to receive PIT interrupts in regular mode (non-virtual wire mode) or something else? Thanks Vivek
