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

[Cédric Le Goater]

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