[PATCH] powerpc: Fix definition of SIAR and SDAR registers

Paul Mackerras paulus at ozlabs.org
Fri May 13 13:35:46 AEST 2016

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 at redhat.com>

Acked-by: Paul Mackerras <paulus at ozlabs.org>

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