From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
To: Julien Grall <julien.grall@arm.com>,
Stefano Stabellini <sstabellini@kernel.org>
Cc: Wei Liu <wei.liu2@citrix.com>,
ian.jackson@eu.citrix.com, peter.huangpeng@huawei.com,
xen-devel@lists.xen.org, Shannon Zhao <shannon.zhao@linaro.org>,
Shannon Zhao <zhaoshenglong@huawei.com>
Subject: Re: [PATCH v2 16/17] libxc/xc_dom_arm: Copy ACPI tables to guest space
Date: Wed, 20 Jul 2016 10:09:29 -0400 [thread overview]
Message-ID: <c388b913-fe1f-a3e8-94dd-fee9bb7f9427@oracle.com> (raw)
In-Reply-To: <a6b4653d-6137-8239-aacc-982b39c022e0@arm.com>
On 07/20/2016 09:41 AM, Julien Grall wrote:
>
>
> On 20/07/2016 14:33, Boris Ostrovsky wrote:
>> On 07/20/2016 08:33 AM, Julien Grall wrote:
>>> Hi,
>>>
>>> On 14/07/16 14:37, Stefano Stabellini wrote:
>>>> On Wed, 13 Jul 2016, Julien Grall wrote:
>>>>> Hello,
>>>>>
>>>>> On 12/07/2016 17:58, Boris Ostrovsky wrote:
>>>>>> On 07/12/2016 12:10 PM, Julien Grall wrote:
>>>>>>> On 12/07/2016 16:08, Boris Ostrovsky wrote:
>>>>>>>> On 07/12/2016 10:57 AM, Shannon Zhao wrote:
>>>>>>> It will affect some others part of the guest if we don't increment
>>>>>>> the
>>>>>>> "maxmem" requested by the user. For ARM the ACPI blob will be
>>>>>>> exposed
>>>>>>> at a specific address that is outside of the guest RAM (see the
>>>>>>> guest
>>>>>>> memory layout in public/arch-arm.h).
>>>>>>>
>>>>>>> We chose this solution over putting in the RAM because the ACPI
>>>>>>> tables
>>>>>>> are not easily relocatable (compare to the device tree, initrd and
>>>>>>> kernel) so we could not take advantage of superpage in both stage-2
>>>>>>> (hypervisor) and stage-1 (kernel) page table.
>>>>>>
>>>>>> Maybe this is something ARM-specific then. For x86 we will want to
>>>>>> keep
>>>>>> maxmem unchanged.
>>>>>
>>>>> I don't think what I described in my previous mail is
>>>>> ARM-specific. The
>>>>> pressure will be more important on the TLBs, if Xen does not use
>>>>> superpage in
>>>>> the stage 2 page tables (i.e EPT for x86) no matter the architecture.
>>>>>
>>>>> IHMO, this seems to be a bigger drawback compare to add few more
>>>>> kilobytes to
>>>>> maxmem in the toolstack for the ACPI blob. You will loose them when
>>>>> creating
>>>>> the intermediate page table in any case.
>>>>
>>>> I agree with Julien. On ARM we have to increase maxmem because I don't
>>>> think that shattering a superpage is acceptable for just a few KBs. In
>>>> fact, it's not much about increasing maxmem, but it's about keeping
>>>> the
>>>> allocation of guest memory to the value passed by the user in
>>>> "memory",
>>>> so that it can be done in the most efficient way possible. (I am
>>>> assuming users are going to allocate VMs of 2048MB, rather than
>>>> 2049MB.)
>>>>
>>>> I wouldn't want to end up adding to the performance tuning page on the
>>>> wiki "Make sure to add 1 more MB to the memory of your VM to get the
>>>> most out of the system."
>>>>
>>>> I know that the location of the ACPI blob on x86 is different in guest
>>>> memory space, but it seems to me that the problem would be the
>>>> same. Do
>>>> you have 1 gigabyte pages in stage-2 on x86? If so, I would think
>>>> twice
>>>> about this. Otherwise, if you only have 4K and 2MB allocations,
>>>> then it
>>>> might not make that much of a difference.
>>>
>>> Looking at the x86 code, 1 gigabyte pages seems to be supported.
>>>
>>> Boris, do you have any opinions on this?
>>
>>
>> I don't think I understand the superpage shattering argument. In x86
>> the tables live in regular RAM and a guest is free to use those
>> addresses as regular memory.
>>
>> This apparently is different from how ARM manages the tables (you said
>> in an earlier message that they are not part of RAM) so I can see that
>> taking memory from RAM allocation to store the tables may affect how
>> mapping is done, potentially causing GB pages to be broken.
>>
>> In fact (and I am totally speculating here) padding memory for x86 may
>> actually *cause* shattering because we will have (for example) 2049MB of
>> RAM to deal with.
>
> Correct me if I am wrong. On your series you are populating the page
> at a specific address for the ACPI tables separately to the RAM
> allocation. So you will shatter GB pages if the user provides 2048MB
> because the ACPI tables is accounted in the 2048MB.
And to be honest I am not convinced this was a well selected address
(0xfc000000). I am actually thinking about moving it down (this may
require changing dsdt.asl). I don't know whether I will actually do it
in this version but it is certainly a possibility.
-boris
>
> The plan is to call setmaxmem with the size of the RAM + size of the
> ACPI tales. The RAM will still be 2048MB and therefore GB pages may be
> used.
>
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next prev parent reply other threads:[~2016-07-20 14:09 UTC|newest]
Thread overview: 130+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-23 3:16 [PATCH v2 00/17] Xen ARM DomU ACPI support Shannon Zhao
2016-06-23 3:16 ` [PATCH v2 01/17] libxl/arm: Factor out codes for generating DTB Shannon Zhao
2016-06-23 3:16 ` [PATCH v2 02/17] libxc: Add placeholders for ACPI tables blob and size Shannon Zhao
2016-06-23 3:16 ` [PATCH v2 03/17] libxl/arm: Add a configuration option for ARM DomU ACPI Shannon Zhao
2016-06-23 13:39 ` Stefano Stabellini
2016-06-23 14:34 ` Shannon Zhao
2016-06-27 10:40 ` Julien Grall
2016-07-07 15:30 ` Wei Liu
2016-07-12 3:40 ` Shannon Zhao
2016-07-12 9:22 ` Julien Grall
2016-07-12 11:33 ` Wei Liu
2016-07-12 14:17 ` Shannon Zhao
2016-07-12 14:33 ` Wei Liu
2016-07-12 14:45 ` Shannon Zhao
2016-07-13 7:54 ` Shannon Zhao
2016-07-13 9:20 ` Julien Grall
2016-07-13 9:48 ` Shannon Zhao
2016-07-13 10:03 ` Julien Grall
2016-07-15 8:00 ` Shannon Zhao
2016-07-15 8:07 ` Shannon Zhao
2016-07-18 19:40 ` Stefano Stabellini
2016-07-19 10:40 ` Wei Liu
2016-07-19 10:44 ` Ian Jackson
2016-06-23 15:53 ` Julien Grall
2016-06-23 3:16 ` [PATCH v2 04/17] libxl/arm: prepare for constructing ACPI tables Shannon Zhao
2016-06-23 13:37 ` Stefano Stabellini
2016-06-23 14:23 ` Shannon Zhao
2016-06-23 14:27 ` Stefano Stabellini
2016-06-23 16:18 ` Julien Grall
2016-06-23 3:16 ` [PATCH v2 05/17] libxl/arm: Construct ACPI RSDP table Shannon Zhao
2016-06-23 3:16 ` [PATCH v2 06/17] libxl/arm: Construct ACPI XSDT table Shannon Zhao
2016-06-23 3:16 ` [PATCH v2 07/17] libxl/arm: Construct ACPI GTDT table Shannon Zhao
2016-06-23 15:00 ` Stefano Stabellini
2016-06-23 16:19 ` Julien Grall
2016-06-23 16:26 ` Julien Grall
2016-06-23 16:58 ` Julien Grall
2016-06-27 1:44 ` Shannon Zhao
2016-06-27 10:17 ` Julien Grall
2016-06-29 9:29 ` Shannon Zhao
2016-06-29 9:42 ` Julien Grall
2016-06-29 13:41 ` Shannon Zhao
2016-07-05 16:42 ` Stefano Stabellini
2016-07-06 9:50 ` Julien Grall
2016-07-06 10:16 ` Stefano Stabellini
2016-06-23 3:16 ` [PATCH v2 08/17] libxl/arm: Factor MPIDR computing codes out as a helper Shannon Zhao
2016-06-23 16:29 ` Julien Grall
2016-06-23 3:16 ` [PATCH v2 09/17] libxl/arm: Construct ACPI MADT table Shannon Zhao
2016-06-23 16:36 ` Julien Grall
2016-06-23 3:16 ` [PATCH v2 10/17] libxl/arm: Construct ACPI FADT table Shannon Zhao
2016-06-23 3:16 ` [PATCH v2 11/17] libxl/arm: Construct ACPI DSDT table Shannon Zhao
2016-06-23 14:50 ` Stefano Stabellini
2016-06-23 16:42 ` Julien Grall
2016-06-27 1:50 ` Shannon Zhao
2016-06-23 17:03 ` Julien Grall
2016-06-27 6:01 ` Shannon Zhao
2016-06-27 10:29 ` Julien Grall
2016-06-27 12:05 ` Boris Ostrovsky
2016-06-28 11:03 ` Shannon Zhao
2016-06-28 13:41 ` Boris Ostrovsky
2016-06-29 18:58 ` Boris Ostrovsky
2016-07-01 7:58 ` Shannon Zhao
2016-07-01 10:18 ` Julien Grall
2016-07-01 14:42 ` Boris Ostrovsky
2016-07-01 15:14 ` Julien Grall
2016-06-23 3:16 ` [PATCH v2 12/17] libxl/arm: Add a helper to calculate the ACPI table checksum Shannon Zhao
2016-06-23 17:05 ` Julien Grall
2016-06-23 3:17 ` [PATCH v2 13/17] libxl/arm: Link all ACPI tables into one buffer Shannon Zhao
2016-06-23 17:10 ` Julien Grall
2016-06-23 3:17 ` [PATCH v2 14/17] libxl/arm: Factor finalise_one_memory_node as a gerneric function Shannon Zhao
2016-06-23 3:17 ` [PATCH v2 15/17] libxl/arm: Add ACPI module Shannon Zhao
2016-06-23 18:35 ` Julien Grall
2016-06-25 3:22 ` Shannon Zhao
2016-06-27 9:48 ` Julien Grall
2016-06-23 3:17 ` [PATCH v2 16/17] libxc/xc_dom_arm: Copy ACPI tables to guest space Shannon Zhao
2016-06-23 18:46 ` Julien Grall
2016-06-27 6:25 ` Shannon Zhao
2016-06-27 10:49 ` Julien Grall
2016-06-27 12:11 ` Boris Ostrovsky
2016-07-05 17:13 ` Stefano Stabellini
2016-07-06 9:46 ` Julien Grall
2016-07-06 10:12 ` Stefano Stabellini
2016-07-12 3:47 ` Shannon Zhao
2016-07-12 9:25 ` Julien Grall
2016-07-12 11:35 ` Wei Liu
2016-07-12 14:42 ` Shannon Zhao
2016-07-12 14:50 ` Wei Liu
2016-07-12 14:57 ` Shannon Zhao
2016-07-12 15:08 ` Boris Ostrovsky
2016-07-12 15:13 ` Wei Liu
2016-07-12 15:21 ` Boris Ostrovsky
2016-07-12 16:05 ` Wei Liu
2016-07-12 16:10 ` Julien Grall
2016-07-12 16:58 ` Boris Ostrovsky
2016-07-13 15:22 ` Julien Grall
2016-07-13 17:08 ` Boris Ostrovsky
2016-07-14 11:15 ` Wei Liu
2016-07-15 9:39 ` Shannon Zhao
2016-07-19 10:38 ` Wei Liu
2016-07-20 6:52 ` Shannon Zhao
2016-07-20 9:32 ` Wei Liu
2016-07-25 7:56 ` Shannon Zhao
2016-07-28 11:10 ` Julien Grall
2016-07-14 11:29 ` Julien Grall
2016-07-14 13:37 ` Stefano Stabellini
2016-07-20 12:33 ` Julien Grall
2016-07-20 13:33 ` Boris Ostrovsky
2016-07-20 13:41 ` Julien Grall
2016-07-20 14:09 ` Boris Ostrovsky [this message]
2016-07-20 17:28 ` Stefano Stabellini
2016-07-20 19:51 ` Boris Ostrovsky
2016-07-21 17:53 ` Stefano Stabellini
2016-07-21 18:23 ` Julien Grall
2016-07-21 18:54 ` Stefano Stabellini
2016-07-21 19:14 ` Julien Grall
2016-07-21 21:15 ` Stefano Stabellini
2016-07-25 8:38 ` George Dunlap
2016-07-25 9:46 ` Julien Grall
2016-07-25 22:06 ` Stefano Stabellini
2016-07-25 22:46 ` Boris Ostrovsky
2016-07-25 23:40 ` Stefano Stabellini
2016-07-26 1:17 ` Boris Ostrovsky
2016-07-28 11:06 ` Julien Grall
2016-07-28 12:42 ` Shannon Zhao
2016-08-02 11:01 ` Wei Liu
2016-08-03 19:20 ` Julien Grall
2016-08-04 10:17 ` Wei Liu
2016-08-02 11:01 ` Wei Liu
2016-07-07 15:35 ` Wei Liu
2016-06-23 3:17 ` [PATCH v2 17/17] libxl/arm: Initialize domain param HVM_PARAM_CALLBACK_IRQ Shannon Zhao
2016-06-23 18:48 ` Julien Grall
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