linux-kernel - Re: [PATCH] xen/pv: Add PV specific legacy

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Message-ID: <2eb1fdec-6cc0-7f62-3d4f-adc5dba9971e@oracle.com>
Date:   Tue, 19 Mar 2019 19:06:49 -0400
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Jennifer Herbert <jennifer.herbert@...rix.com>, x86@...nel.org,
        xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org
Cc:     Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] xen/pv: Add PV specific legacy_pic struct to expose
 legacy IRQs.

On 3/19/19 4:02 PM, Jennifer Herbert wrote:
> The ACPI tables doesn't always contain all IRQs for legacy devices
> such as RTC.  Since no PIC controller is visible for a PV linux guest,
> under Xen, legacy_pic currently defaults to the null_legacy_pic - with
> reports no legacy IRQs.  Since the commit "rtc: cmos: Do not assume
> irq 8 for rtc when there are no legacy irqs" by Hans de Goede
> (commit id: a1e23a42f1bdc00e32fc4869caef12e4e6272f26), the rtc now
> incorrectly decides it has no irq it can use, for some hardware.
>
> This patch rectifies the problem by providing a xen legacy_pic
> struct, which is much like the null_legacy_pic except that it
> reports NR_IRQS_LEGACY irqs.

I assume this is for dom0?

Could there be the same problem with PVH dom0? (and if yes then this
should probably go into arch/x86/xen/enlighten.c).

-boris