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Wed, 8 Apr 2020 16:48:39 +0000 (GMT) Received: from b03ledav004.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 181FA7805E; Wed, 8 Apr 2020 16:48:29 +0000 (GMT) Received: from LeoBras (unknown [9.85.164.111]) by b03ledav004.gho.boulder.ibm.com (Postfix) with ESMTP; Wed, 8 Apr 2020 16:48:29 +0000 (GMT) Message-ID: Subject: Re: [PATCH v3 1/1] ppc/crash: Reset spinlocks during crash From: Leonardo Bras To: Michael Ellerman , Nicholas Piggin , Alexios Zavras , Benjamin Herrenschmidt , Christophe Leroy , Greg Kroah-Hartman , Enrico Weigelt , Paul Mackerras , peterz@infradead.org, Thomas Gleixner Date: Wed, 08 Apr 2020 13:48:21 -0300 In-Reply-To: <87v9majhh2.fsf@mpe.ellerman.id.au> References: <20200401000020.590447-1-leonardo@linux.ibm.com> <871rp6t9di.fsf@mpe.ellerman.id.au> <02e74be19534ab1db2f16a0c89ecb164e380c12a.camel@linux.ibm.com> <1585895551.7o9oa0ey62.astroid@bobo.none> <87v9majhh2.fsf@mpe.ellerman.id.au> Content-Type: multipart/signed; micalg="pgp-sha256"; protocol="application/pgp-signature"; boundary="=-2xsxWow0iUbl6nYPXNaI" User-Agent: Evolution 3.34.4 (3.34.4-1.fc31) MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138, 18.0.676 definitions=2020-04-07_10:2020-04-07, 2020-04-07 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 mlxscore=0 phishscore=0 mlxlogscore=939 adultscore=0 malwarescore=0 priorityscore=1501 bulkscore=0 clxscore=1015 lowpriorityscore=0 spamscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2004080125 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" --=-2xsxWow0iUbl6nYPXNaI Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Wed, 2020-04-08 at 22:21 +1000, Michael Ellerman wrote: [...] > > On the other hand, busting the rtas.lock could be dangerous, because > > it's code we can't control. > >=20 > > According with LoPAR, for both of these rtas-calls, we have: > >=20 > > For the PowerPC External Interrupt option: The call must be reentrant > > to the number of processors on the platform. > > For the PowerPC External Interrupt option: The argument call buffer for > > each simultaneous call must be physically unique. >=20 > Oh well spotted. Where is that in the doc? In the current LoPAR available on OpenPower Foundation, it's on page 170, '7.3.10.2 ibm,set-xive' and '7.3.10.3 ibm,int-off'. > > Which I think means this rtas-calls can be done simultaneously. >=20 > I think so too. I'll read PAPR in the morning and make sure. >=20 > > Would it mean that busting the rtas.lock for these calls would be safe? >=20 > What would be better is to make those specific calls not take the global > RTAS lock to begin with. >=20 > We should be able to just allocate the rtas_args on the stack, it's only > ~80 odd bytes. And then we can use rtas_call_unlocked() which doesn't > take the global lock. Good idea. I will try getting some work done on this. 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