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Date: Wed, 26 Oct 2016 17:09:52 +0200
From: Igor Mammedov <imammedo@redhat.com>
Message-ID: <20161026170952.18c02dbb@nial.brq.redhat.com>
In-Reply-To: <1477416484-29054-1-git-send-email-wei.liu2@citrix.com>
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Subject: Re: [Qemu-devel] [PATCH RFC] acpi: don't build acpi tables for xen
 hvm guests
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To: Wei Liu <wei.liu2@citrix.com>
Cc: qemu-devel@nongnu.org, Anthony PERARD <anthony.perard@citrix.com>, Xen-devel <xen-devel@lists.xenproject.org>, Stefano Stabellini <sstabellini@kernel.org>

On Tue, 25 Oct 2016 18:28:04 +0100
Wei Liu <wei.liu2@citrix.com> wrote:

> Xen's toolstack is in charge of building ACPI tables. Skip acpi table
> building if running on Xen.
> 
> This issue is discovered due to direct kernel boot on Xen doesn't boot
> anymore, because the new ACPI tables cause the guest to exceed its
> memory allocation limit.
> 
> Reported-by: Sander Eikelenboom <linux@eikelenboom.it>
> Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Question is:
Why does xen guest get ACPI tables from QEMU instead of using
Xen provided ones.
Maybe it's firmware issue i.e. firmware side shouldn't load
ACPI tables from QEMU provided fwcfg file and load Xen provided instead.

> ---
> Cc: Anthony PERARD <anthony.perard@citrix.com>
> Cc: Stefano Stabellini <sstabellini@kernel.org>
> 
> RFC because I'm not sure this is the best way to fix it.
> ---
>  hw/i386/acpi-build.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index a26a4bb..2cdff12 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -45,6 +45,7 @@
>  #include "sysemu/tpm_backend.h"
>  #include "hw/timer/mc146818rtc_regs.h"
>  #include "sysemu/numa.h"
> +#include "hw/xen/xen.h"
>  
>  /* Supported chipsets: */
>  #include "hw/acpi/piix4.h"
> @@ -2865,6 +2866,11 @@ void acpi_setup(void)
>          return;
>      }
>  
> +    if (xen_enabled()) {
> +        ACPI_BUILD_DPRINTF("Xen enabled. Bailing out.\n");
> +        return;
> +    }
> +
>      build_state = g_malloc0(sizeof *build_state);
>  
>      acpi_set_pci_info();