From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: [PATCH] clarify SHUTDOWN_suspend additional argument Date: Thu, 8 May 2014 11:21:43 +0100 Message-ID: <536B5AB7.3060409@citrix.com> References: <1399543914.9513.34.camel@kazak.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1399543914.9513.34.camel@kazak.uk.xensource.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Ian Campbell Cc: xen-devel@lists.xensource.com, David Vrabel , Stefano Stabellini List-Id: xen-devel@lists.xenproject.org On 08/05/14 11:11, Ian Campbell wrote: > On Wed, 2014-05-07 at 14:05 +0100, Stefano Stabellini wrote: >> SCHEDOP_shutdown has a third argument that is unused on HVM and ARM >> guests. Those guests pass 0 instead. Clarify the behaviour in the >> hypercall description. >> >> Signed-off-by: Stefano Stabellini > Acked-by: Ian Campbell > > But: >> diff --git a/xen/include/public/sched.h b/xen/include/public/sched.h >> index a30b11d..c170556 100644 >> --- a/xen/include/public/sched.h >> +++ b/xen/include/public/sched.h >> @@ -77,8 +77,9 @@ >> * @arg == pointer to sched_shutdown_t structure. >> * >> * If the sched_shutdown_t reason is SHUTDOWN_suspend then this >> - * hypercall takes an additional extra argument which should be the >> - * MFN of the guest's start_info_t. >> + * hypercall takes an additional extra argument which should be: >> + * - the MFN of the guest's start_info_t for x86 PV guests; >> + * - 0 for x86 HVM guests and arm and arm64 guests. > Is this strictly true or is the argument ignored for those guests? > (Requiring it to be zero doesn't conflict with that hence the ack) Having recently played with code here, I believe it is as follows. * Xen does absolutely nothing with the value whatsoever. * PV Migration *must* check the value (and indeed converts it to a pfn for transit) * HVM guests (including arm for these purposes) don't have easy access to the register, and just transmit the Xen architectural state blob as-is. Therefore, the only requirement I can see is that PV guests must point it at the start_info_t mfn. ~Andrew > >> * >> * In addition, which reason is SHUTDOWN_suspend this hypercall >> * returns 1 if suspend was cancelled or the domain was merely > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xen.org > http://lists.xen.org/xen-devel