PowerPC KVM-PR issue

[Christian Zigotzky]

On 11 June 2020 at 04:47 pm, Christian Zigotzky wrote:
> On 10 June 2020 at 01:23 pm, Christian Zigotzky wrote:
>> On 10 June 2020 at 11:06 am, Christian Zigotzky wrote:
>>> On 10 June 2020 at 00:18 am, Christian Zigotzky wrote:
>>>> Hello,
>>>>
>>>> KVM-PR doesn't work anymore on my Nemo board [1]. I figured out 
>>>> that the Git kernels and the kernel 5.7 are affected.
>>>>
>>>> Error message: Fienix kernel: kvmppc_exit_pr_progint: emulation at 
>>>> 700 failed (00000000)
>>>>
>>>> I can boot virtual QEMU PowerPC machines with KVM-PR with the 
>>>> kernel 5.6 without any problems on my Nemo board.
>>>>
>>>> I tested it with QEMU 2.5.0 and QEMU 5.0.0 today.
>>>>
>>>> Could you please check KVM-PR on your PowerPC machine?
>>>>
>>>> Thanks,
>>>> Christian
>>>>
>>>> [1] https://en.wikipedia.org/wiki/AmigaOne_X1000
>>>
>>> I figured out that the PowerPC updates 5.7-1 [1] are responsible for 
>>> the KVM-PR issue. Please test KVM-PR on your PowerPC machines and 
>>> check the PowerPC updates 5.7-1 [1].
>>>
>>> Thanks
>>>
>>> [1] 
>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=d38c07afc356ddebaa3ed8ecb3f553340e05c969
>>>
>>>
>> I tested the latest Git kernel with Mac-on-Linux/KVM-PR today. 
>> Unfortunately I can't use KVM-PR with MoL anymore because of this 
>> issue (see screenshots [1]). Please check the PowerPC updates 5.7-1.
>>
>> Thanks
>>
>> [1]
>> - 
>> https://i.pinimg.com/originals/0c/b3/64/0cb364a40241fa2b7f297d4272bbb8b7.png
>> - 
>> https://i.pinimg.com/originals/9a/61/d1/9a61d170b1c9f514f7a78a3014ffd18f.png
>>
> Hi All,
>
> I bisected today because of the KVM-PR issue.
>
> Result:
>
> 9600f261acaaabd476d7833cec2dd20f2919f1a0 is the first bad commit
> commit 9600f261acaaabd476d7833cec2dd20f2919f1a0
> Author: Nicholas Piggin <npiggin at gmail.com>
> Date:   Wed Feb 26 03:35:21 2020 +1000
>
>     powerpc/64s/exception: Move KVM test to common code
>
>     This allows more code to be moved out of unrelocated regions. The
>     system call KVMTEST is changed to be open-coded and remain in the
>     tramp area to avoid having to move it to entry_64.S. The custom 
> nature
>     of the system call entry code means the hcall case can be made more
>     streamlined than regular interrupt handlers.
>
>     mpe: Incorporate fix from Nick:
>
>     Moving KVM test to the common entry code missed the case of HMI and
>     MCE, which do not do __GEN_COMMON_ENTRY (because they don't want to
>     switch to virt mode).
>
>     This means a MCE or HMI exception that is taken while KVM is 
> running a
>     guest context will not be switched out of that context, and KVM won't
>     be notified. Found by running sigfuz in guest with patched host on
>     POWER9 DD2.3, which causes some TM related HMI interrupts (which are
>     expected and supposed to be handled by KVM).
>
>     This fix adds a __GEN_REALMODE_COMMON_ENTRY for those handlers to add
>     the KVM test. This makes them look a little more like other handlers
>     that all use __GEN_COMMON_ENTRY.
>
>     Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
>     Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
>     Link: 
> https://lore.kernel.org/r/20200225173541.1549955-13-npiggin@gmail.com
>
> :040000 040000 ec21cec22d165f8696d69532734cb2985d532cb0 
> 87dd49a9cd7202ec79350e8ca26cea01f1dbd93d M    arch
>
> -----
>
> The following commit is the problem: powerpc/64s/exception: Move KVM 
> test to common code [1]
>
> These changes were included in the PowerPC updates 5.7-1. [2]
>
> Another test:
>
> git checkout d38c07afc356ddebaa3ed8ecb3f553340e05c969 (PowerPC updates 
> 5.7-1 [2] ) -> KVM-PR doesn't work.
>
> After that: git revert d38c07afc356ddebaa3ed8ecb3f553340e05c969 -m 1 
> -> KVM-PR works.
>
> Could you please check the first bad commit? [1]
>
> Thanks,
> Christian
>
>
> [1] 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=9600f261acaaabd476d7833cec2dd20f2919f1a0
> [2] 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=d38c07afc356ddebaa3ed8ecb3f553340e05c969

Hi All,

I tried to revert the __GEN_REALMODE_COMMON_ENTRY fix for the latest Git 
kernel and for the stable kernel 5.7.2 but without any success. There 
was lot of restructuring work during the kernel 5.7 development time in 
the PowerPC area so it isn't possible reactivate the old code. That 
means we have lost the whole KVM-PR support. I also reported this issue 
to Alexander Graf two days ago. He wrote: "Howdy :). It looks pretty 
broken. Have you ever made a bisect to see where the problem comes from?"

Please check the KVM-PR code.

Thanks,
Christian