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Mon, 16 Dec 2019 23:20:10 +0000 (GMT) Received: from b03ledav005.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id BF401BE04F; Mon, 16 Dec 2019 23:19:57 +0000 (GMT) Received: from morokweng.localdomain (unknown [9.85.177.201]) by b03ledav005.gho.boulder.ibm.com (Postfix) with ESMTPS; Mon, 16 Dec 2019 23:19:56 +0000 (GMT) References: <20191216041924.42318-1-aik@ozlabs.ru> <20191216041924.42318-4-aik@ozlabs.ru> User-agent: mu4e 1.2.0; emacs 26.2 From: Thiago Jung Bauermann To: Alexey Kardashevskiy Subject: Re: [PATCH kernel v2 3/4] powerpc/pseries/iommu: Separate FW_FEATURE_MULTITCE to put/stuff features In-reply-to: <20191216041924.42318-4-aik@ozlabs.ru> Date: Mon, 16 Dec 2019 20:19:46 -0300 Message-ID: <877e2vuact.fsf@morokweng.localdomain> MIME-Version: 1.0 Content-Type: text/plain X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.95,18.0.572 definitions=2019-12-16_07:2019-12-16,2019-12-16 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 mlxlogscore=999 clxscore=1015 bulkscore=0 adultscore=0 mlxscore=0 spamscore=0 phishscore=0 lowpriorityscore=0 impostorscore=0 priorityscore=1501 suspectscore=18 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1910280000 definitions=main-1912160195 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: Michael Anderson , Ram Pai , kvm-ppc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, David Gibson Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Alexey Kardashevskiy writes: > H_PUT_TCE_INDIRECT allows packing up to 512 TCE updates into a single > hypercall; H_STUFF_TCE can clear lots in a single hypercall too. > > However, unlike H_STUFF_TCE (which writes the same TCE to all entries), > H_PUT_TCE_INDIRECT uses a 4K page with new TCEs. In a secure VM > environment this means sharing a secure VM page with a hypervisor which > we would rather avoid. > > This splits the FW_FEATURE_MULTITCE feature into FW_FEATURE_PUT_TCE_IND > and FW_FEATURE_STUFF_TCE. "hcall-multi-tce" in > the "/rtas/ibm,hypertas-functions" device tree property sets both; > the "multitce=off" kernel command line parameter disables both. > > This should not cause behavioural change. > > Signed-off-by: Alexey Kardashevskiy Reviewed-by: Thiago Jung Bauermann Tested-by: Thiago Jung Bauermann -- Thiago Jung Bauermann IBM Linux Technology Center