Re: [Xen-devel] [PATCH] x86/HVM: tie RTC emulation mode to enabling of Viridian emulation

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Tue, Jul 02, 2013 at 11:22:21AM +0100, Jan Beulich wrote:
> >>> On 02.07.13 at 11:51, Tim Deegan <tim@xxxxxxx> wrote:
> > At 10:27 +0100 on 02 Jul (1372760862), Jan Beulich wrote:
> >> >>> On 02.07.13 at 11:11, Tim Deegan <tim@xxxxxxx> wrote:
> >> > At 08:02 +0100 on 02 Jul (1372752161), Jan Beulich wrote:
> >> >> As the mode not conforming to the hardware specification (by allowing
> >> >> the guest to skip the REG C reads in its interrupt handler) is a
> >> >> Viridian invention, it seems logical to tie this mode to that extension
> >> >> being enabled. If the extension is disabled, proper hardware emulation
> >> >> will be done instead.
> >> >> 
> >> >> The main thing necessary here is the synchronization of the RTC
> >> >> emulation code and the setting of the respective flag in hvmloader's
> >> >> creation of the ACPI WAET table.
> >> >> 
> >> >> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> >> > 
> >> > Wasn't this going to have its own param, defaulting to off on create and
> >> > to on on migrate?  I suspect most people just leave the viridian flag on
> >> > for all domains.
> >> 
> >> In which case there would be no behavioral difference to what
> >> we're going to release with 4.3. (That's leaving aside the fact that
> >> I think people doing so is not the best practice.)
> > 
> > Why not?  The Viridian interfaces is pretty well essential for running
> > recent Windows, and shouldn't be harmful for other OSes.
> 
> Shouldn't. But as we learned it occasionally is - Linux when built
> without CONFIG_XEN_PVHVM detects the HyperV functionality,
> and tried using HyperV functionality that Xen doesn't really emulate
> (see commits 32068f65 ["x86: Hyper-V: register clocksource only if
> its advertised"] and db34bbb7 ["X86: Add a check to catch Xen
> emulation of Hyper-V"]).

Shouldn't those patches be in stable tree by now?

> 
> Jan
> 
> 
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