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From: Julien Grall <julien.grall@arm.com>
To: Shannon Zhao <zhaoshenglong@huawei.com>, xen-devel@lists.xen.org
Cc: sstabellini@kernel.org, wei.liu2@citrix.com,
	Steve Capper <Steve.Capper@arm.com>,
	ian.jackson@eu.citrix.com, peter.huangpeng@huawei.com,
	shannon.zhao@linaro.org
Subject: Re: [PATCH RESEND 03/14] libxc: Add placeholders for ACPI tables blob and size
Date: Thu, 16 Jun 2016 12:04:09 +0100	[thread overview]
Message-ID: <576287A9.5060504@arm.com> (raw)
In-Reply-To: <57628350.8060709@huawei.com>

Hello Shannon,

On 16/06/16 11:45, Shannon Zhao wrote:
>>> On 2016/6/7 21:06, Julien Grall wrote:
>>>>> That's its own mechanism I think and UEFI wants all the memory maps
>>>>> under its control. And it's same for QEMU(x86 and ARM) and also for Xen
>>>>> on x86. You can have a look at the OvmfPkg/AcpiPlatformDxe/Xen.c which
>>>>> is used for x86 Xen DomU.
>>>>
>>>> UEFI cannot control the memory map because it is not capable to know
>>>> what a region is used for (such as magic pages, grant table...).
>>>>
>>>> In the case of domU for x86, the ACPI table are located in predefine
>>>> physical address by hvmloader.
>>> The truth is that hvmloader puts the tables at address
>>> ACPI_PHYSICAL_ADDRESS(0x000EA020), but UEFI will install the tables and
>>> relocate them as well. You can see OvmfPkg/AcpiPlatformDxe/Xen.c in edk2
>>> source code.
>>>
>>> So I think it's same with ARM except x86 puts the tables at one fixed
>>> address while ARM dynamically computes the address and passes the
>>> address information to UEFI through dts.
>>>
>>> Yeah, of course we can let ARM put the tables at one fixed address and
>>> also it doesn't need the ACPI module to pass the address and let UEFI
>>> find the RSDP table from the fixed address. But what's the difference
>>> between the fixed and dynamicall ones? Because both ways UEFI will
>>> install and relocate the tables.
>>
>> You seem to think that OVMF is the only UEFI implementation available
>> and its behavior is set in stone. Can you quote the UEFI spec stating
>> the ACPI tables will always be relocated?
>>
>> If not, putting the ACPI module right in the middle of memory is not the
>> wisest choice because the tables can not be easily relocated like other
>> modules (DT, Kernel, initramfs).
>>
> The ACPI tables are put after the DT. How could you say the ACPI is in
> the middle while DT not?

Because the position of the DT in the memory is defined by the Linux 
boot ABI (see section 4.b in Documentation/arm/Booting).

>
>> My suggestion to put the ACPI tables at a static address outside the RAM
>> is to let the choice to the firmware to do whatever it wants without
>> impacting the performance of a kernel if it ever decides to keep in
>> place the tables.
>>
>> However, this static address is from the toolstack point of view. The
>> firmware should not assume any static address because the guest memory
>> layout is not part of the ABI for Xen ARM (i.e it can be modified
>> between two releases). This is to allow us reshuffling the layout to
>> make space for new features.
>>
> Sure? Currently for Xen x86, edk2 uses XEN_ACPI_PHYSICAL_ADDRESS to find
> RSDP. If we put the tables at another address, DomU will fail to boot.

I am not sure to follow here. Why do you mention x86 here? My point was 
only for ARM and we are not tight to what x86 does.

>
>>>
>>>> I really don't see any reason that would
>>>> prevent us to do the same on ARM.
>>>>
>>>> If the UEFI firmware wants to relocate the tables, then fine. But we
>>>> should also think about any firmware which may not relocate the tables.
>>> Can you name one firmware except the UEFI?
>>
>> Sorry I meant any other UEFI implementation (i.e other than OVMF) may
>> not relocate the tables.
> So please tell me the name of other UEFI implementation.

What is the point? All our decision should be based on the specification 
and not ONE specific implementation.

Regards,

-- 
Julien Grall

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  reply	other threads:[~2016-06-16 11:04 UTC|newest]

Thread overview: 104+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-05-31  5:02 [PATCH RESEND 00/14] Xen ARM DomU ACPI support Shannon Zhao
2016-05-31  5:02 ` [PATCH RESEND 01/14] libxl/arm: Fix the function name in error log Shannon Zhao
2016-06-03 19:25   ` Wei Liu
2016-06-17 10:46     ` Wei Liu
2016-06-20  1:12       ` Shannon Zhao
2016-05-31  5:02 ` [PATCH RESEND 02/14] libxl/arm: Factor out codes for generating DTB Shannon Zhao
2016-06-03 19:25   ` Wei Liu
2016-05-31  5:02 ` [PATCH RESEND 03/14] libxc: Add placeholders for ACPI tables blob and size Shannon Zhao
2016-06-06 10:00   ` Stefano Stabellini
2016-06-06 12:16     ` Wei Liu
2016-06-06 14:20       ` Shannon Zhao
2016-06-07 11:05   ` Julien Grall
2016-06-07 11:13     ` Shannon Zhao
2016-06-07 11:27       ` Julien Grall
2016-06-07 11:35         ` Shannon Zhao
2016-06-07 11:42           ` Julien Grall
2016-06-07 11:59             ` Shannon Zhao
2016-06-07 12:06               ` Julien Grall
2016-06-07 12:32                 ` Shannon Zhao
2016-06-07 13:06                   ` Julien Grall
2016-06-16  6:53                     ` Shannon Zhao
2016-06-16 10:21                       ` Julien Grall
2016-06-16 10:45                         ` Shannon Zhao
2016-06-16 11:04                           ` Julien Grall [this message]
2016-06-16 10:49                   ` Wei Liu
2016-06-16 10:53                     ` Shannon Zhao
2016-06-16 11:04                       ` Wei Liu
2016-06-07 12:02             ` Julien Grall
2016-06-07 12:27               ` Shannon Zhao
2016-05-31  5:02 ` [PATCH RESEND 04/14] tools: add ACPI tables relevant definitions Shannon Zhao
2016-06-06 10:04   ` Stefano Stabellini
2016-06-06 10:11     ` Julien Grall
2016-06-06 10:27       ` Shannon Zhao
2016-06-06 12:16         ` Wei Liu
2016-06-06 14:19           ` Shannon Zhao
2016-06-22  3:24           ` Shannon Zhao
2016-06-22  8:35             ` Julien Grall
2016-06-22  8:50               ` Shannon Zhao
2016-06-22  8:55                 ` Julien Grall
2016-06-22  9:38             ` [PATCH RESEND 04/14] tools: add ACPI tables relevant definitions (and more) Wei Liu
2016-06-22 10:06               ` Shannon Zhao
2016-05-31  5:02 ` [PATCH RESEND 05/14] libxl/arm: Construct ACPI GTDT table Shannon Zhao
2016-06-06 11:40   ` Stefano Stabellini
2016-06-06 11:52     ` Julien Grall
2016-06-06 12:04       ` Stefano Stabellini
2016-06-06 14:31         ` Shannon Zhao
2016-06-06 14:50           ` Stefano Stabellini
2016-06-06 15:42             ` Julien Grall
2016-06-07  9:41               ` Stefano Stabellini
2016-06-06 15:35         ` Julien Grall
2016-06-07  9:48           ` Stefano Stabellini
2016-06-07 11:55             ` Wei Liu
2016-06-17  3:29     ` Shannon Zhao
2016-06-17  8:17       ` Julien Grall
2016-06-17  9:15         ` Stefano Stabellini
2016-06-17 13:27           ` Julien Grall
2016-06-06 12:18   ` Wei Liu
2016-06-07 11:02     ` Julien Grall
2016-06-07 11:19   ` Julien Grall
2016-06-07 11:30     ` Shannon Zhao
2016-06-07 11:36       ` Julien Grall
2016-06-07 11:39         ` Shannon Zhao
2016-06-07 11:43           ` Julien Grall
2016-05-31  5:02 ` [PATCH RESEND 06/14] libxl/arm: Construct ACPI FADT table Shannon Zhao
2016-06-07 13:17   ` Julien Grall
2016-06-07 14:13     ` Shannon Zhao
2016-06-07 14:14       ` Julien Grall
2016-05-31  5:02 ` [PATCH RESEND 07/14] libxl/arm: Construct ACPI DSDT table Shannon Zhao
2016-06-07 13:42   ` Julien Grall
2016-06-16  6:25     ` Shannon Zhao
2016-06-16  9:44       ` Julien Grall
2016-06-16 10:01         ` Stefano Stabellini
2016-05-31  5:03 ` [PATCH RESEND 08/14] libxl/arm: Construct ACPI MADT table Shannon Zhao
2016-06-07 13:40   ` Julien Grall
2016-05-31  5:03 ` [PATCH RESEND 09/14] libxl/arm: Construct ACPI XSDT table Shannon Zhao
2016-05-31  5:03 ` [PATCH RESEND 10/14] libxl/arm: Construct ACPI RSDP table Shannon Zhao
2016-05-31  5:03 ` [PATCH RESEND 11/14] libxl/arm: Initialize domain param HVM_PARAM_CALLBACK_IRQ Shannon Zhao
2016-05-31  5:03 ` [PATCH RESEND 12/14] libxl/arm: Add ACPI module Shannon Zhao
2016-06-07 13:47   ` Julien Grall
2016-05-31  5:03 ` [PATCH RESEND 13/14] libxl/arm: initialize memory information of ACPI blob Shannon Zhao
2016-06-06 11:40   ` Stefano Stabellini
2016-06-06 14:35     ` Shannon Zhao
2016-05-31  5:03 ` [PATCH RESEND 14/14] libxc/xc_dom_core: Copy ACPI tables to guest memory space Shannon Zhao
2016-05-31 10:47 ` [PATCH RESEND 00/14] Xen ARM DomU ACPI support Julien Grall
2016-05-31 14:19   ` Shannon Zhao
2016-06-03 19:24 ` Wei Liu
2016-06-03 20:02   ` Konrad Rzeszutek Wilk
2016-06-03 20:20     ` Boris Ostrovsky
2016-06-03 20:27       ` Wei Liu
2016-06-03 20:36         ` Boris Ostrovsky
2016-06-06 11:41 ` Stefano Stabellini
2016-06-06 12:26 ` Wei Liu
2016-06-06 15:37   ` Boris Ostrovsky
2016-06-06 16:50     ` Boris Ostrovsky
2016-06-07 10:54       ` Julien Grall
2016-06-07 14:24         ` Boris Ostrovsky
2016-06-06 15:48   ` Julien Grall
2016-06-07  1:07     ` Shannon Zhao
2016-06-07 11:00       ` Julien Grall
2016-06-16 11:20         ` Wei Liu
2016-06-16 13:25           ` Boris Ostrovsky
2016-06-17 10:14             ` Wei Liu
2016-06-17  2:03           ` Shannon Zhao
2016-06-17  8:18           ` Julien Grall

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