On Mon, 2016-05-30 at 10:04 +0200, Thomas Huth wrote: > On 13.05.2016 05:35, Paul Mackerras wrote: > > On Thu, May 12, 2016 at 01:26:44PM +0200, Thomas Huth wrote: > > > The SIAR and SDAR registers are available twice, one time as SPRs > > > 780 / 781 (unprivileged, but read-only), and one time as the SPRs > > > 796 / 797 (privileged, but read and write). The Linux kernel code > > > currently uses the unprivileged SPRs - while this is OK for reading, > > > writing to that register of course does not work. > > > Since the KVM code tries to write to this register, too (see the mtspr > > > in book3s_hv_rmhandlers.S), the contents of this register sometimes get > > > lost for the guests, e.g. during migration of a VM. > > > To fix this issue, simply switch to the privileged SPR numbers instead. > > > > > > Signed-off-by: Thomas Huth <thuth@xxxxxxxxxx> > > > > Acked-by: Paul Mackerras <paulus@xxxxxxxxxx> > > *ping* > > Michael, could you please pick this patch up? I think it should rather > go through the generic powerpc tree instead of kvm-ppc, since it also > affects other parts than just KVM... Yeah that's actually why I hesitated to merge it, because I want to know what the broader implications are ... I have also gone back and confirmed that the 796/797 numbers exist and are correct on all CPUs we support, which involved a lot of digging through PDFs. cheers -- To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
