Re: [PATCH v4] target: ppc: Use MSR_HVB bit to get the target endianness for memory dump

[Vaibhav Jain]

Thanks for fixing this Narayana,

Narayana Murty N <nnmlinux@linux.ibm.com> writes:

> Currently on PPC64 qemu always dumps the guest memory in
> Big Endian (BE) format even though the guest running in Little Endian
> (LE) mode. So crash tool fails to load the dump as illustrated below:
>
> Log :
> $ virsh dump DOMAIN --memory-only dump.file
>
> Domain 'DOMAIN' dumped to dump.file
>
> $ crash vmlinux dump.file
>
> <snip>
> crash 8.0.2-1.el9
>
> WARNING: endian mismatch:
>           crash utility: little-endian
>           dump.file: big-endian
>
> WARNING: machine type mismatch:
>           crash utility: PPC64
>           dump.file: (unknown)
>
> crash: dump.file: not a supported file format
> <snip>
>
> This happens because cpu_get_dump_info() passes cpu->env->has_hv_mode
> to function ppc_interrupts_little_endian(), the cpu->env->has_hv_mode
> always set for powerNV even though the guest is not running in hv mode.
> The hv mode should be taken from msr_mask MSR_HVB bit
> (cpu->env.msr_mask & MSR_HVB). This patch fixes the issue by passing
> MSR_HVB value to ppc_interrupts_little_endian() in order to determine
> the guest endianness.
>
> The crash tool also expects guest kernel endianness should match the
> endianness of the dump.
>
> The patch was tested on POWER9 box booted with Linux as host in
> following cases:
>
> Host-Endianess Qemu-Target-Machine                Qemu-Generated-Guest
>                                                   Memory-Dump-Format
> BE             powernv(OPAL/PowerNV)                   LE
> BE             powernv(OPAL/PowerNV)                   BE
> LE             powernv(OPAL/PowerNV)                   LE
> LE             powernv(OPAL/PowerNV)                   BE
> LE             pseries(OPAL/PowerNV/pSeries) KVMHV     LE
> LE             pseries TCG                             LE
>
> Fixes: 5609400a4228 ("target/ppc: Set the correct endianness for powernv 
> memory
> dumps")
> Signed-off-by: Narayana Murty N <nnmlinux@linux.ibm.com>

Reviewed-by: Vaibhav Jain<vaibhav@linux.ibm.com>

-- 
Cheers
~ Vaibhav