From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
Shannon Zhao <zhaoshenglong@huawei.com>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
ard.biesheuvel@linaro.org, stefano.stabellini@citrix.com,
david.vrabel@citrix.com,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
julien.grall@citrix.com, xen-devel@lists.xen.org,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
linux-efi@vger.kernel.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
ian.campbell@citrix.com, Shannon Zhao <shannon.zhao@linaro.org>,
peter.huangpeng@huawei.com, Len Brown <lenb@kernel.org>,
"open list:ACPI" <linux-acpi@vger.kernel.org>
Subject: Re: [PATCH v4 01/17] Xen: ACPI: Hide UART used by Xen
Date: Wed, 10 Feb 2016 23:29:31 +0100 [thread overview]
Message-ID: <44113385.2QnPtvxQx0@vostro.rjw.lan> (raw)
In-Reply-To: <alpine.DEB.2.02.1602091116240.27008@kaball.uk.xensource.com>
On Tuesday, February 09, 2016 11:19:02 AM Stefano Stabellini wrote:
> On Mon, 8 Feb 2016, Rafael J. Wysocki wrote:
> > On Monday, February 08, 2016 10:57:01 AM Stefano Stabellini wrote:
> > > On Sat, 6 Feb 2016, Rafael J. Wysocki wrote:
> > > > On Fri, Feb 5, 2016 at 4:05 AM, Shannon Zhao <zhaoshenglong@huawei.com> wrote:
> > > > > From: Shannon Zhao <shannon.zhao@linaro.org>
> > > > >
> > > > > ACPI 6.0 introduces a new table STAO to list the devices which are used
> > > > > by Xen and can't be used by Dom0. On Xen virtual platforms, the physical
> > > > > UART is used by Xen. So here it hides UART from Dom0.
> > > > >
> > > > > Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
> > > > > Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> > > >
> > > > Well, this doesn't look right to me.
> > > >
> > > > We need to find a nicer way to achieve what you want.
> > >
> > > I take that you are talking about how to honor the STAO table in Linux.
> > > Do you have any concrete suggestions?
> >
> > I do.
> >
> > The last hunk of the patch is likely what it needs to be, although I'm
> > not sure if the place it is added to is the right one. That's a minor thing,
> > though.
> >
> > The other part is problematic. Not that as it doesn't work, but because of
> > how it works. With these changes the device will be visible to the OS (in
> > fact to user space even), but will never be "present". I'm not sure if
> > that's what you want?
> >
> > It might be better to add a check to acpi_bus_type_and_status() that will
> > evaluate the "should ignore?" thing and return -ENODEV if this is true. This
> > way the device won't be visible at all.
>
> Something like below? Actually your suggestion is better, thank you!
>
> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> index 78d5f02..4778c51 100644
> --- a/drivers/acpi/scan.c
> +++ b/drivers/acpi/scan.c
> @@ -1455,6 +1455,9 @@ static int acpi_bus_type_and_status(acpi_handle handle, int *type,
> if (ACPI_FAILURE(status))
> return -ENODEV;
>
> + if (acpi_check_device_is_ignored(handle))
> + return -ENODEV;
> +
> switch (acpi_type) {
> case ACPI_TYPE_ANY: /* for ACPI_ROOT_OBJECT */
> case ACPI_TYPE_DEVICE:
>
I thought about doing that under ACPI_TYPE_DEVICE, because it shouldn't be
applicable to the other types. But generally, yes.
Plus I'd move the table checks to acpi_scan_init(), so the UART address can
be a static variable in scan.c.
Also maybe rename acpi_check_device_is_ignored() to something like
acpi_device_should_be_hidden().
Thanks,
Rafael
next prev parent reply other threads:[~2016-02-10 22:28 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-05 3:05 [PATCH v4 00/17] Add ACPI support for Xen Dom0 on ARM64 Shannon Zhao
2016-02-05 3:05 ` [PATCH v4 01/17] Xen: ACPI: Hide UART used by Xen Shannon Zhao
2016-02-06 10:23 ` Rafael J. Wysocki
2016-02-08 10:57 ` Stefano Stabellini
2016-02-08 22:25 ` Rafael J. Wysocki
2016-02-09 11:19 ` Stefano Stabellini
2016-02-10 22:29 ` Rafael J. Wysocki [this message]
2016-02-11 16:04 ` Stefano Stabellini
2016-02-11 22:22 ` Rafael J. Wysocki
2016-02-12 11:50 ` Stefano Stabellini
2016-02-12 12:57 ` Rafael J. Wysocki
2016-02-29 2:02 ` Shannon Zhao
2016-02-05 3:05 ` [PATCH v4 02/17] xen/grant-table: Move xlated_setup_gnttab_pages to common place Shannon Zhao
2016-02-05 3:05 ` [PATCH v4 03/17] Xen: xlate: Use page_to_xen_pfn instead of page_to_pfn Shannon Zhao
2016-02-05 3:05 ` [PATCH v4 04/17] arm/xen: Use xen_xlate_map_ballooned_pages to setup grant table Shannon Zhao
2016-02-05 3:05 ` [PATCH v4 05/17] xen: memory : Add new XENMAPSPACE type XENMAPSPACE_dev_mmio Shannon Zhao
2016-02-08 11:43 ` Stefano Stabellini
2016-02-05 3:05 ` [PATCH v4 06/17] Xen: ARM: Add support for mapping platform device mmio Shannon Zhao
2016-02-05 3:05 ` [PATCH v4 07/17] Xen: ARM: Add support for mapping AMBA " Shannon Zhao
2016-02-05 3:05 ` [PATCH v4 08/17] Xen: public/hvm: sync changes of HVM_PARAM_CALLBACK_VIA ABI from Xen Shannon Zhao
2016-02-05 3:05 ` [PATCH v4 09/17] xen/hvm/params: Add a new delivery type for event-channel in HVM_PARAM_CALLBACK_IRQ Shannon Zhao
2016-02-05 3:05 ` [PATCH v4 10/17] arm/xen: Get event-channel irq through HVM_PARAM when booting with ACPI Shannon Zhao
2016-02-05 3:05 ` [PATCH v4 11/17] ARM: XEN: Move xen_early_init() before efi_init() Shannon Zhao
2016-02-05 3:05 ` [PATCH v4 12/17] ARM64: ACPI: Check if it runs on Xen to enable or disable ACPI Shannon Zhao
2016-02-05 3:05 ` [PATCH v4 13/17] ARM: Xen: Document UEFI support on Xen ARM virtual platforms Shannon Zhao
2016-02-08 11:31 ` Stefano Stabellini
2016-02-05 3:05 ` [PATCH v4 14/17] XEN: EFI: Move x86 specific codes to architecture directory Shannon Zhao
2016-02-05 3:05 ` [PATCH v4 15/17] ARM64: XEN: Add a function to initialize Xen specific UEFI runtime services Shannon Zhao
2016-02-05 3:05 ` [PATCH v4 16/17] FDT: Add a helper to get specified name subnode Shannon Zhao
2016-02-05 14:15 ` Stefano Stabellini
2016-02-09 5:04 ` Rob Herring
2016-02-23 11:13 ` Shannon Zhao
2016-02-24 14:53 ` Rob Herring
2016-02-05 3:05 ` [PATCH v4 17/17] Xen: EFI: Parse DT parameters for Xen specific UEFI Shannon Zhao
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