From: Paul Mackerras <paulus@ozlabs.org>
To: Thomas Huth <thuth@redhat.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>,
linuxppc-dev@lists.ozlabs.org,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
kvm-ppc@vger.kernel.org, Alexander Graf <agraf@suse.de>,
Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Subject: Re: [PATCH] powerpc: Fix definition of SIAR and SDAR registers
Date: Fri, 13 May 2016 13:35:46 +1000 [thread overview]
Message-ID: <20160513033546.GA22018@oak.ozlabs.ibm.com> (raw)
In-Reply-To: <1463052404-18092-1-git-send-email-thuth@redhat.com>
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@redhat.com>
Acked-by: Paul Mackerras <paulus@ozlabs.org>
next prev parent reply other threads:[~2016-05-13 3:36 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-12 11:26 [PATCH] powerpc: Fix definition of SIAR and SDAR registers Thomas Huth
2016-05-13 3:35 ` Paul Mackerras [this message]
2016-05-30 8:04 ` Thomas Huth
2016-05-30 23:27 ` Michael Ellerman
2016-05-31 10:17 ` Michael Ellerman
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