linux-kernel - Re: [PATCH v2 5/9] xen/pvh: Prevent PVH guests from using PIC, RTC and IOAPIC

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Date:   Thu, 2 Feb 2017 16:40:55 +0000
From:   Roger Pau Monné <roger.pau@...rix.com>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>
CC:     <JGross@...e.com>, <xen-devel@...ts.xenproject.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 5/9] xen/pvh: Prevent PVH guests from using PIC, RTC
 and IOAPIC

On Thu, Feb 02, 2017 at 11:30:19AM -0500, Boris Ostrovsky wrote:
> On 02/02/2017 10:35 AM, Roger Pau Monné wrote:
> > On Thu, Jan 26, 2017 at 02:41:28PM -0500, Boris Ostrovsky wrote:
> >> Make sure they don't use these devices since they are not emulated
> >> for unprivileged PVH guest.
> > This description seems weird for what it's actually done. AFAICT you are not
> > really preventing the guest from using the PIC or the IO APIC, because this is
> > fetched from the MADT table (or should be fetched from there in any case).
> 
> This was meant to say that we don't want to use ACPI_IRQ_MODEL_[IOA]PIC
> since we don't support SCI (which is expected on x86 to be one of the two).

Hm, right. At some point (ie: when PCI-passthrough is implemented) we will be
providing an IO APIC and a SCI through it. Or would we rather always use the
event channel SCI?

Roger.