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Re: [PATCH v4 6/6] xen/arm: mpu: Implement a dummy enable_secondary_cpu_mm
- To: Ayan Kumar Halder <ayankuma@xxxxxxx>
- From: Luca Fancellu <Luca.Fancellu@xxxxxxx>
- Date: Tue, 29 Oct 2024 09:58:13 +0000
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- Cc: Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Bertrand Marquis <Bertrand.Marquis@xxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>
- Delivery-date: Tue, 29 Oct 2024 09:58:37 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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- Thread-topic: [PATCH v4 6/6] xen/arm: mpu: Implement a dummy enable_secondary_cpu_mm
> On 29 Oct 2024, at 09:41, Jan Beulich <jbeulich@xxxxxxxx> wrote:
>
> On 29.10.2024 10:30, Luca Fancellu wrote:
>> Hi Jan,
>>
>>> On 29 Oct 2024, at 08:08, Jan Beulich <jbeulich@xxxxxxxx> wrote:
>>>
>>> On 28.10.2024 18:38, Ayan Kumar Halder wrote:
>>>> On 28/10/2024 15:01, Jan Beulich wrote:
>>>>> On 28.10.2024 15:39, Ayan Kumar Halder wrote:
>>>>>> On 28/10/2024 12:55, Jan Beulich wrote:
>>>>>>> On 28.10.2024 13:45, Ayan Kumar Halder wrote:
>>>>>>>> --- a/xen/arch/Kconfig
>>>>>>>> +++ b/xen/arch/Kconfig
>>>>>>>> @@ -6,11 +6,13 @@ config PHYS_ADDR_T_32
>>>>>>>>
>>>>>>>> config NR_CPUS
>>>>>>>> int "Maximum number of CPUs"
>>>>>>>> + range 1 1 if ARM && MPU
>>>>>>>> range 1 16383
>>>>>>>> default "256" if X86
>>>>>>>> default "8" if ARM && RCAR3
>>>>>>>> default "4" if ARM && QEMU
>>>>>>>> default "4" if ARM && MPSOC
>>>>>>>> + default "1" if ARM && MPU
>>>>>>>> default "128" if ARM
>>>>>>>> help
>>>>>>>> Controls the build-time size of various arrays and bitmaps
>>>>>>> I'm afraid I can't easily tell whether MPU can be used together with
>>>>>>> any of
>>>>>>> RCAR3, QEMU, or MPSOC. If it can, the new default line would need to
>>>>>>> move
>>>>>>> up, as it's the first one that has a match on its condition which is
>>>>>>> being
>>>>>>> used.
>>>>>> MPU cannot be used with any of the existing platforms.
>>>>> That is - qemu can't emulate such an environment, i.e. even QEMU and MPU
>>>>> don't go together?
>>>>
>>>> Qemu has support for Aarch32 MPU at EL2 and EL1 (ie R52). As far as I am
>>>> aware, there is no support for Aarch64 MPU in Qemu (ie R82).
>>>>
>>>> Even for R52, I could not get the upstream Qemu working (emulating some
>>>> Arm reference platform).
>>>>
>>>> I could get the Xilinx fork of Qemu (https://github.com/Xilinx/qemu)
>>>> working which emulates AMD's SoC using R52.
>>>>
>>>> However, this should not impact the current patch. There is no Qemu in
>>>> xen/arch/arm/platforms/*.
>>>
>>> Aiui that's not relevant. There is a QEMU item in
>>> xen/arch/arm/platforms/Kconfig.
>>> I continue to fail to see why that couldn't be selected together with MPU.
>>> Yet if
>>> it can be, you'd end up with a default of 4, not 1, if it actually _is_
>>> selected.
>>> Alternatively QEMU (and maybe also RCAR3 and MPSOC) need to be mutually
>>> exclusive
>>> with MPU. Hmm, looks like that's already the case, by patch 2 suppressing
>>> the
>>> "Platform Support" prompt. While that looks fragile to me, I'm sorry for the
>>> noise then.
>>
>> Are you suggesting to move "default "1" if ARM && MPU” right after “default
>> "256" if X86”?
>
> Yes.
Makes sense!
With that:
Reviewed-by: Luca Fancellu <luca.fancellu@xxxxxxx>
>
> Jan
|
