Re: [PATCH] target/ppc/mmu_common: Fix SRR1/MSR error code on Book-E

[Vitaly Cheptsov]

Hi Cédric,

> and the default ppce500 machine has enough devices for the purpose ?

We cannot test much without a predictable timer emulation on QEMU, sometimes we 
have fairly random freezes, but otherwise the basics work ok. I will let you 
know in case we find something more or less reproducible.

Best,
Vitaly

> On 21 Jan 2022, at 20:33, Cédric Le Goater <clg@kaod.org> wrote:
> 
> Hello Vitaly,
> 
> On 1/21/22 10:33, Vitaly Cheptsov wrote:
>> Hi Cédric,
>>> This looks correct and even fixing an issue that Mario reported
>>> on the TCG e6500 CPU with a kernel + KVM compiled in :
>>> 
>>>  
>>> https://lore.kernel.org/all/R5JFVM$911E343FF81933B99D53FD0992D8848F@locati.it/
>>> 
>>> KVM has some issues also with the e6500 but that's another problem
>>> I think.
>> Glad to hear that. Could you schedule the inclusion of the patch in 6.2.1 or 
>> 6.3 please?
> 
> 7.0 it should be.
> 
>>> What is your environment ? Which QEMU machine ? Can you provide a
>>> command line ?
>> We have an in-house RTOS at ISP RAS, which we use to run some environmental 
>> tests on QEMU.
> 
> not a Linux. Diversity is good for the models.
> 
>> The target hardware in this particular example is a QorIQ P3041-based board.
> 
> and the default ppce500 machine has enough devices for the purpose ?
> 
> Thanks,
> 
> C.
> 
>> The command line approximately looks like this:
>> qemu-system-ppc -cpu e500mc -M ppce500 -m 128M -icount 1 -kernel 
>> /path/to/kernel.elf -serial tcp::1111,server,nodelay
>>> Could you please resend the patch in a non attached way ?  See :
>>> 
>>>  https://www.qemu.org/docs/master/devel/submitting-a-patch.html
>>> 
>>> and copy qemu-devel.
>> Yes, sure. Have just done that.
>> Best regards,
>> Vitaly
>>> On 21 Jan 2022, at 11:17, Cédric Le Goater <clg@kaod.org> wrote:
>>> 
>>> Hello Vitaly
>>> 
>>> On 1/21/22 01:02, Vitaly Cheptsov wrote:
>>>> Hello,
>>>> PowerPC e500mc defines MSR bit 35 differently from most other PowerPC 
>>>> variants. In particular, for e500mc this is GS (Guest Supervisor) bit[1], 
>>>> while for others it is NOEXEC GUARD bit[2].
>>>> QEMU ignores this architectural difference when handling the exceptions of 
>>>> attempting to run not executable code on e500mc, and mistakenly sets the 
>>>> GS bit[3][4].
>>>> Setting this bit eventually leads to crashes, because although QEMU does 
>>>> not support Guest Supervisor mode on e500mc, it still requires it to be 
>>>> disabled[5].
>>> 
>>> This looks correct and even fixing an issue that Mario reported
>>> on the TCG e6500 CPU with a kernel + KVM compiled in :
>>> 
>>>  
>>> https://lore.kernel.org/all/R5JFVM$911E343FF81933B99D53FD0992D8848F@locati.it/
>>> 
>>> KVM has some issues also with the e6500 but that's another problem
>>> I think.
>>> 
>>> 
>>> What is your environment ? Which QEMU machine ? Can you provide a
>>> command line ?
>>> 
>>> Could you please resend the patch in a non attached way ?  See :
>>> 
>>>  https://www.qemu.org/docs/master/devel/submitting-a-patch.html
>>> 
>>> and copy qemu-devel.
>>> 
>>> Thanks,
>>> 
>>> C.
>>> 
>>> 
>>>> Best regards,
>>>> Vitaly
>>>> [1] https://www.nxp.com/docs/en/reference-manual/E500MCRM.pdf, 2.7.1 MSR
>>>> [2] https://openpowerfoundation.org/?resource_lib=power-isa-version-3-0, 
>>>> 6.5.5 Instruction Storage Interrupt
>>>> [3] https://github.com/qemu/qemu/blob/v6.2.0/target/ppc/mmu_common.c#L1426
>>>> [4] 
>>>> https://github.com/qemu/qemu/blob/v6.2.0/target/ppc/excp_helper.c#L414-L416
>>>> [5] 
>>>> https://github.com/qemu/qemu/blob/v6.2.0/target/ppc/mmu_helper.c#L1078-L1080
>>> 
>

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