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Fri, 7 Jul 2023 08:42:58 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A8E1F2004B; Fri, 7 Jul 2023 08:42:55 +0000 (GMT) Received: from [9.43.6.151] (unknown [9.43.6.151]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Fri, 7 Jul 2023 08:42:55 +0000 (GMT) Message-ID: Date: Fri, 7 Jul 2023 14:12:54 +0530 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.12.0 Subject: Re: [PATCH v5 3/3] ppc: Enable 2nd DAWR support on p10 Content-Language: en-US To: David Gibson Cc: qemu-ppc@nongnu.org, mikey@neuling.org, kvm@vger.kernel.org, mst@redhat.com, mpe@ellerman.id.au, cohuck@redhat.com, qemu-devel@nongnu.org, groug@kaod.org, paulus@samba.org, clg@kaod.org, pbonzini@redhat.com, ravi.bangoria@amd.com References: <20210412114433.129702-1-ravi.bangoria@linux.ibm.com> <20210412114433.129702-4-ravi.bangoria@linux.ibm.com> From: Shivaprasad G Bhat In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: GH0cxobMMVQVYaXnGAqgR_Uu3zFDWWzt X-Proofpoint-ORIG-GUID: qKGIMe0_oXr0HA773PwGY1RG_epAtZTm X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.254,Aquarius:18.0.957,Hydra:6.0.591,FMLib:17.11.176.26 definitions=2023-07-07_05,2023-07-06_02,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 mlxscore=0 mlxlogscore=699 spamscore=0 malwarescore=0 adultscore=0 lowpriorityscore=0 impostorscore=0 suspectscore=0 phishscore=0 clxscore=1011 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2305260000 definitions=main-2307070078 Received-SPF: pass client-ip=148.163.156.1; envelope-from=sbhat@linux.ibm.com; helo=mx0a-001b2d01.pphosted.com X-Spam_score_int: -10 X-Spam_score: -1.1 X-Spam_bar: - X-Spam_report: (-1.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, HK_RANDOM_REPLYTO=0.999, NICE_REPLY_A=-0.091, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: YJIyCnVYohsdKLvf@yekko.fra02v.mail.ibm.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Hi David, All, I am revisiting/reviving this patch. On 5/5/21 11:20, David Gibson wrote: > On Wed, Apr 21, 2021 at 11:50:40AM +0530, Ravi Bangoria wrote: >> Hi David, >> >> On 4/19/21 10:23 AM, David Gibson wrote: >>> On Mon, Apr 12, 2021 at 05:14:33PM +0530, Ravi Bangoria wrote: >>> > Since we have released versions with POWER10 support, but no DAWR1, in > theory we need a capability so new qemu with old machine types don't > gain guest visible features that the same machine types on older qemus > had. > > Except.. there's a loophole we might use to sidestep that. The > current POWER10 CPU modelled in qemu is a DD1 - which I strongly > suspect will never appear outside of IBM. I'm pretty sure we want to > replace that with a DD2. > > While the modelled CPU is DD1, I think it's pretty reasonable to say > our POWER10 support hasn't yet stabilized, and it would therefore be > ok to simply add DAWR1 on POWER10 unconditionally, as long as we do it > before we switch over to DD2. As POWER10 DD2 switch over has already happened, the need for new/separate capability for dawr1 still holds. So, I am keeping it as is. Posting the next version after rebase. Thanks, Shivaprasad >>> I'm wondering if we're actually just better off setting the pa feature >>> just based on the guest CPU model. TCG will be broken if you try to >>> use it, but then, it already is. AFAIK there's no inherent reason we >>> couldn't implement DAWR support in TCG, it's just never been worth the >>> trouble. >> Correct. Probably there is no practical usecase for DAWR in TCG mode. >> >> Thanks, >> Ravi >>