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

[Vitaly Cheptsov]

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?

> 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. The target hardware in this particular example is a QorIQ 
P3041-based board. 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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