Re: [Qemu-devel] [PATCH] PowerPC: Add TM bits into msr_mask

[Simon Guo <wei.guo.simon@gmail.com>]

Hi David,
On Mon, Mar 05, 2018 at 05:22:33PM +1100, David Gibson wrote:
> On Wed, Feb 28, 2018 at 09:51:37AM +0800, wei.guo.simon@gmail.com wrote:
> > From: Simon Guo <wei.guo.simon@gmail.com>
> > 
> > During migration, cpu_post_load() will use msr_mask to determine which
> > PPC MSR bits will be sync to the target side. Hardware Transaction
> > Memory(HTM) has been supported since Power8. This patch adds TM/TS bits
> > into msr_mask for Power8, so that transactional application can be
> > migrated across qemu.
> > 
> > Signed-off-by: Simon Guo <wei.guo.simon@gmail.com>
> 
> Sorry I've taken a while to respond to this.
> 
> This addresses a real bug, but doesn't get the details quite right.
> 
> First, the MSR_TM bit is *already* included in the msr_mask for POWER8
> (it's a little above the context for this patch), though TS0 and TS1
> were not.
> 
> Second, all MSR bits are sent to the far side, it's just that without
> them in the MSR mask they'll be dropped instead of re-inserted into
> KVM.  That's the only reason the msr_mask is relevant to KVM (and TCG
> doesn't support HTM anyway).  The commit message needs to make that clearer.
> 

Thanks for the comments. I have sent v2 to correct the above.

Regards,
- Simon