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 for <linuxppc-dev@lists.ozlabs.org>; Mon, 30 May 2016 18:04:53 +1000 (AEST)
Subject: Re: [PATCH] powerpc: Fix definition of SIAR and SDAR registers
To: Michael Ellerman <mpe@ellerman.id.au>
References: <1463052404-18092-1-git-send-email-thuth@redhat.com>
 <20160513033546.GA22018@oak.ozlabs.ibm.com>
Cc: Paul Mackerras <paulus@ozlabs.org>, 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>
From: Thomas Huth <thuth@redhat.com>
Message-ID: <574BF41F.4050305@redhat.com>
Date: Mon, 30 May 2016 10:04:47 +0200
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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@redhat.com>
> 
> Acked-by: Paul Mackerras <paulus@ozlabs.org>

*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...

Thanks,
 Thomas