From: Shannon Zhao <zhaoshenglong@huawei.com>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>,
Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
"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: Mon, 29 Feb 2016 10:02:36 +0800 [thread overview]
Message-ID: <56D3A6BC.8020005@huawei.com> (raw)
In-Reply-To: <1667812.hY9vsC2epc@vostro.rjw.lan>
On 2016/2/12 6:22, Rafael J. Wysocki wrote:
> On Thursday, February 11, 2016 04:04:14 PM Stefano Stabellini wrote:
>> > On Wed, 10 Feb 2016, Rafael J. Wysocki wrote:
>>> > > 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.
>> >
>> > I was pondering about it myself. Maybe an ACPI_TYPE_PROCESSOR object
>> > could theoretically be hidden with the STAO?
> But this patch won't check for it anyway, will it?
>
> It seems to be only checking against the UART address or have I missed
> anything?
>
>> > I added the check before
>> > the switch because I thought that there would be no harm in being
>> > caution about it.
>> >
>> >
>>> > > 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().
>> >
>> > Both make sense. Shannon, are you happy to make these changes?
> Plus maybe make acpi_device_should_be_hidden() print a (KERN_INFO) message
> when it decides to hide something?
Ok, will update this patch. Thanks a lot!
--
Shannon
next prev parent reply other threads:[~2016-02-29 2:03 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
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 [this message]
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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