Re: [Xen-devel] [PATCH 4/9] xen: arm: turn vtimer traps for cp32/64 and sysreg into #undef

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2015-01-15 at 12:27 +0000, Julien Grall wrote:
> Hi Ian,
> 
> On 15/01/15 10:26, Ian Campbell wrote:
> > I'm looking into the vtimer masking and ctxt switching the irq state
> > now, once I've got that going exposing the ptimer directly to guests
> > ought to be pretty simple.
> 
> I don't think we can expose directly the physical timer to the guest.
> 
> If the guest tries to read CNTPCT_EL0, it will read the number of ticks
> since the host is up.

Yes, and they should expect that I think, that's the point of the
distinction between v and p timer. Of course maybe by providing it with
an offset until now maybe we've painted ourselves into a corner, which
sucks :-/

Ian.


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