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Tue, 28 May 2024 07:05:30 GMT Received: from smtpav05.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1BC512004D; Tue, 28 May 2024 07:05:28 +0000 (GMT) Received: from smtpav05.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 5962B2004B; Tue, 28 May 2024 07:05:26 +0000 (GMT) Received: from li-3c92a0cc-27cf-11b2-a85c-b804d9ca68fa.in.ibm.com (unknown [9.109.199.72]) by smtpav05.fra02v.mail.ibm.com (Postfix) with ESMTP; Tue, 28 May 2024 07:05:26 +0000 (GMT) From: Aditya Gupta To: Mahesh J Salgaonkar , Madhavan Srinivasan , Nicholas Piggin , =?utf-8?q?C=C3=A9dric_Le_Goater?= Cc: , , Daniel Henrique Barboza Subject: [PATCH v4 04/11] target/ppc: Fix regression due to Power10 and Power11 having same PCR Date: Tue, 28 May 2024 12:35:08 +0530 Message-ID: <20240528070515.117160-5-adityag@linux.ibm.com> X-Mailer: git-send-email 2.45.1 In-Reply-To: <20240528070515.117160-1-adityag@linux.ibm.com> References: <20240528070515.117160-1-adityag@linux.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-GUID: efOyM60DwXSXV5wN-wGaG3ACmcKWexbm X-Proofpoint-ORIG-GUID: 73la1HzJBVrAu_U0Q5e1ciHBJbaZH0ov X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1039,Hydra:6.0.650,FMLib:17.12.28.16 definitions=2024-05-28_04,2024-05-27_01,2024-05-17_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 impostorscore=0 suspectscore=0 phishscore=0 clxscore=1015 mlxscore=0 malwarescore=0 adultscore=0 lowpriorityscore=0 spamscore=0 bulkscore=0 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2405010000 definitions=main-2405280050 Received-SPF: pass client-ip=148.163.156.1; envelope-from=adityag@linux.ibm.com; helo=mx0a-001b2d01.pphosted.com X-Spam_score_int: -16 X-Spam_score: -1.7 X-Spam_bar: - X-Spam_report: (-1.7 / 5.0 requ) BAYES_00=-1.9, DKIM_INVALID=0.1, DKIM_SIGNED=0.1, RCVD_IN_MSPIKE_H4=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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Power11 has the same PCR (Processor Compatibility Register) value, as Power10. Due to this, QEMU considers Power11 as a valid compat-mode for Power10, ie. earlier it was possible to run QEMU with '-M pseries,max-compat-mode=power11 --cpu power10' Same PCR also introduced a regression where `-M pseries --cpu power10` boots as Power11 (ie. logical PVR is of Power11, even though PVR is Power10). The regression was due to 'do_client_architecture_support' checking for valid compat modes and finding Power11 to be a valid compat mode for Power10 (it happens even without passing 'max-compat-mode' explicitly). Fix compat-mode issue and regression, by ensuring a future Power processor (with a higher logical_pvr value, eg. P11) cannot be valid compat-mode for an older Power processor (eg. P10) Cc: Cédric Le Goater Cc: Daniel Henrique Barboza Cc: Mahesh J Salgaonkar Cc: Madhavan Srinivasan Cc: Nicholas Piggin Signed-off-by: Aditya Gupta --- Multiple alternative approaches were tried to fix this: 1. New PCR for Power11: No 2. 'Hacky fix': chose (n-1) entry in compat table in case of Power10. Commit: https://github.com/adi-g15-ibm/qemu/commit/c79bd667791883d4fb5e643979ae9c86a97bdf66 Pros: Doesn't require adding a new field Cons: Hacky fix, will need change if Power12 comes with same PCR as Power10 (unlikely) 3. Setting current Processor's .logical_pvr as the max_compat to be checked during CAS (Client Architecture Support). Commit: https://github.com/adi-g15-ibm/qemu/commit/30e430be71c6f3296017177298e54532570c2c87 This causes CAS to not consider Power11 if cpu is Power10 --- --- target/ppc/compat.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/target/ppc/compat.c b/target/ppc/compat.c index 12dd8ae290ca..168a3c06316f 100644 --- a/target/ppc/compat.c +++ b/target/ppc/compat.c @@ -139,6 +139,10 @@ static bool pcc_compat(PowerPCCPUClass *pcc, uint32_t compat_pvr, /* Outside specified range */ return false; } + if (compat->pvr > pcc->logical_pvr) { + /* Older CPU cannot support a newer processor's compat mode */ + return false; + } if (!(pcc->pcr_supported & compat->pcr_level)) { /* Not supported by this CPU */ return false;