Re: [Xen-devel] [PATCH v3 09/35] OvmfPkg/OvmfXen: use a TimerLib instance that depends only on the CPU

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

On Mon, Jul 15, 2019 at 04:22:19PM +0200, Roger Pau Monné wrote:
> On Thu, Jul 04, 2019 at 03:42:07PM +0100, Anthony PERARD wrote:
> > ACPI Timer does not work in a PVH guest, but local APIC works on both
> 
> This is not accurate. It's not that the ACPI timer doesn't work, it's
> just that it's not present. The PM_TMR_BLK should be set to 0 to
> indicate the lack of PM timer support, or else there's something
> broken.

I'll reword that first sentence.

OVMF doesn't look at the PM_TMR_BLK value when initializing that timer,
it only looks at the PCI host bridge device ID because OVMF is built
with QEMU in mind and there are only two possibles choices, QEMU is
running with a piix or q35 machine type, I think.

> > PVH and HVM.
> > 
> > Note that the use of SecPeiDxeTimerLibCpu might be an issue with a
> > driver of type DXE_RUNTIME_DRIVER. I've attemptde to find out which of
>                                           ^ attempted
> > the DXE_RUNTIME_DRIVER uses the TimerLib at runtime. I've done that by
> > replacing the TimerLib evaluation in
> > [LibraryClasses.common.DXE_RUNTIME_DRIVER] by a different one and
> > check every module that uses it (with the --report-file=report build
>   ^ checking
> > option).
> > 
> > ResetSystemRuntimeDxe is calling the TimerLib API at runtime to do the
> > operation "EfiResetCold", so this may never complete if the OS have
> > disabled the Local APIC Timer.
> 
> Thanks, Roger.

Thanks,

-- 
Anthony PERARD

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