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Wed, 14 May 2025 18:53:00 +0000 (GMT) Message-ID: <1a31a22d-183e-43e6-bea1-28a69b4eb6de@linux.ibm.com> Date: Wed, 14 May 2025 13:52:59 -0500 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 09/50] ppc/xive2: Fix irq preempted by lower priority group irq To: Nicholas Piggin , qemu-ppc@nongnu.org Cc: qemu-devel@nongnu.org, =?UTF-8?B?RnLDqWTDqXJpYyBCYXJyYXQ=?= , Glenn Miles , Caleb Schlossin References: <20250512031100.439842-1-npiggin@gmail.com> <20250512031100.439842-10-npiggin@gmail.com> Content-Language: en-US From: Mike Kowal In-Reply-To: <20250512031100.439842-10-npiggin@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=etzfzppX c=1 sm=1 tr=0 ts=6824e690 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=IkcTkHD0fZMA:10 a=dt9VzEwgFbYA:10 a=VnNF1IyMAAAA:8 a=rvxr7Vxs7MPorNA6K-4A:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNTE0MDE2OSBTYWx0ZWRfX2jcN07HWTD4W ZmteNogedqEA93f6NGRby6KHydI46uhilehAx5D1UVE4YEi25DcKRiQLy+tCnD0K+axfbugCqXr Vs+F6X9pCtybspesidSTPBnQipGBpIyC+N4pD4VrNSH6W+I0cSlsV6fQ4+JtkIU/tOY2xe8ocTL Y4rpNsf0iDS5z3/EhDJzh+I/KdlMHRCMpHzjsiNuqOmvQvuMvMY40gd8UbN0vqjLv3yFVEuDBAs r58+69yuyzppWW6KfRJdD0NGobDi2IgCU5+xvLZfh2K6JaLC2thdpvYWHPIY1ej0FeH6JNl/crN cRz5PHwLEB+xwVqNFnSYnbyavpYqxWUgd7iIyH311uvRfylHvTIMSOv9/fP/oEEyi0vXaMgIfVW 97R8nHk3bGhd8RCJfNu/ZlvKKtCFjW6+5k/WVVxeGf2fvw5dTwGZFiiceDKNSuS5RMdAyrtE X-Proofpoint-ORIG-GUID: jQHmFvsh3FwszvhIelru_RNlxJsapAEV X-Proofpoint-GUID: l7n-Sy5BgjdLquWXKN4sFQegAtIMAjVZ X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.0.736,FMLib:17.12.80.40 definitions=2025-05-14_04,2025-05-14_03,2025-02-21_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 lowpriorityscore=0 phishscore=0 mlxscore=0 mlxlogscore=950 bulkscore=0 suspectscore=0 spamscore=0 clxscore=1015 priorityscore=1501 malwarescore=0 adultscore=0 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2505070000 definitions=main-2505140169 Received-SPF: pass client-ip=148.163.156.1; envelope-from=kowal@linux.ibm.com; helo=mx0a-001b2d01.pphosted.com X-Spam_score_int: -26 X-Spam_score: -2.7 X-Spam_bar: -- X-Spam_report: (-2.7 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham 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 On 5/11/2025 10:10 PM, Nicholas Piggin wrote: > From: Glenn Miles > > A problem was seen where uart interrupts would be lost resulting in the > console hanging. Traces showed that a lower priority interrupt was > preempting a higher priority interrupt, which would result in the higher > priority interrupt never being handled. > > The new interrupt's priority was being compared against the CPPR > (Current Processor Priority Register) instead of the PIPR (Post > Interrupt Priority Register), as was required by the XIVE spec. > This allowed for a window between raising an interrupt and ACK'ing > the interrupt where a lower priority interrupt could slip in. Reviewed-by: Michael Kowal Thanks MAK > > Fixes: 26c55b99418 ("ppc/xive2: Process group backlog when updating the CPPR") > Signed-off-by: Glenn Miles > --- > hw/intc/xive2.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/hw/intc/xive2.c b/hw/intc/xive2.c > index 453fe37f18..2b4d0f51be 100644 > --- a/hw/intc/xive2.c > +++ b/hw/intc/xive2.c > @@ -1283,7 +1283,7 @@ bool xive2_tm_irq_precluded(XiveTCTX *tctx, int ring, uint8_t priority) > * priority to know if the thread can take the interrupt now or if > * it is precluded. > */ > - if (priority < alt_regs[TM_CPPR]) { > + if (priority < alt_regs[TM_PIPR]) { > return false; > } > return true;