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Wed, 14 May 2025 14:33:33 +0000 (GMT) Message-ID: Date: Wed, 14 May 2025 09:33:33 -0500 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 12/50] ppc/xive2: Set CPPR delivery should account for group priority To: Nicholas Piggin , qemu-ppc@nongnu.org Cc: qemu-devel@nongnu.org, =?UTF-8?B?RnLDqWTDqXJpYyBCYXJyYXQ=?= , Glenn Miles , Michael Kowal , Caleb Schlossin References: <20250512031100.439842-1-npiggin@gmail.com> <20250512031100.439842-13-npiggin@gmail.com> Content-Language: en-US From: Caleb Schlossin In-Reply-To: <20250512031100.439842-13-npiggin@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: e7-DgOZPpigWcS9EZFcBnRCXqqPwYiqp X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNTE0MDEyNSBTYWx0ZWRfXyPI4MIdOQSAm TjdzoMXMJUytn/e81v12kUAVfox9672rjX+NvQbRdKzCjURp8zVW13TKnK8NSD9yi7bkt0ejTX+ IQS4ZjJ0A5nAHG+KkIj5+sF2l+50TXJPf5ume8YcKGQTqSh6QZy3dDsiA0AJV7X04vaLlHFbeG7 1zjTZxEsrGGQiwzZmCYweOk2TvtBCju4Zb6mj57lw2p8Zfn/uVH0qMEEBCcw24BYtweuFk5Ecj/ v1l+pY5+ZEaD+qSLcElhoiY2Nxszkpp7mDRizyp11jbmjDk9eX++6diwf3sALbBLpRirVUDYLUC M2qMM6bFdRL4HdH1R0YzfJZSnb+H49HwgLTc2wUFYM8TPW5Q0vGjDFaqWHPOqZG9D+kVb/NuiEC txJT8Rsmj6plGQUNblY+euqbgKcgPD7OPpKIcPQf7yi30Pl3WRgOF1nVAzd0NbNdFRU4VwEu X-Proofpoint-ORIG-GUID: dvAvgDPdxPjDE6ClXjcY_fqdWFJIE60Z X-Authority-Analysis: v=2.4 cv=GbEXnRXL c=1 sm=1 tr=0 ts=6824a9c1 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=IkcTkHD0fZMA:10 a=dt9VzEwgFbYA:10 a=VnNF1IyMAAAA:8 a=pGLkceISAAAA:8 a=zSV6phptauE46_GIRisA:9 a=QEXdDO2ut3YA:10 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 adultscore=0 impostorscore=0 clxscore=1015 priorityscore=1501 lowpriorityscore=0 suspectscore=0 mlxlogscore=999 phishscore=0 bulkscore=0 malwarescore=0 mlxscore=0 spamscore=0 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2505070000 definitions=main-2505140125 Received-SPF: pass client-ip=148.163.158.5; envelope-from=calebs@linux.ibm.com; helo=mx0b-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-Mailman-Approved-At: Wed, 14 May 2025 11:10:35 -0400 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 Looks good. Reviewed-by: Caleb Schlossin On 5/11/25 10:10 PM, Nicholas Piggin wrote: > The group interrupt delivery flow selects the group backlog scan if > LSMFB < IPB, but that scan may find an interrupt with a priority >= > IPB. In that case, the VP-direct interrupt should be chosen. This > extends to selecting the lowest prio between POOL and PHYS rings. > > Implement this just by re-starting the selection logic if the > backlog irq was not found or priority did not match LSMFB (LSMFB > is updated so next time around it would see the right value and > not loop infinitely). > > Signed-off-by: Nicholas Piggin > --- > hw/intc/xive2.c | 32 ++++++++++++++++++++++---------- > 1 file changed, 22 insertions(+), 10 deletions(-) > > diff --git a/hw/intc/xive2.c b/hw/intc/xive2.c > index 8ede95b671..de139dcfbf 100644 > --- a/hw/intc/xive2.c > +++ b/hw/intc/xive2.c > @@ -939,7 +939,7 @@ static void xive2_tctx_set_cppr(XiveTCTX *tctx, uint8_t ring, uint8_t cppr) > { > uint8_t *regs = &tctx->regs[ring]; > Xive2Router *xrtr = XIVE2_ROUTER(tctx->xptr); > - uint8_t old_cppr, backlog_prio, first_group, group_level = 0; > + uint8_t old_cppr, backlog_prio, first_group, group_level; > uint8_t pipr_min, lsmfb_min, ring_min; > bool group_enabled; > uint32_t nvp_blk, nvp_idx; > @@ -961,10 +961,12 @@ static void xive2_tctx_set_cppr(XiveTCTX *tctx, uint8_t ring, uint8_t cppr) > * Recompute the PIPR based on local pending interrupts. It will > * be adjusted below if needed in case of pending group interrupts. > */ > +again: > pipr_min = xive_ipb_to_pipr(regs[TM_IPB]); > group_enabled = !!regs[TM_LGS]; > - lsmfb_min = (group_enabled) ? regs[TM_LSMFB] : 0xff; > + lsmfb_min = group_enabled ? regs[TM_LSMFB] : 0xff; > ring_min = ring; > + group_level = 0; > > /* PHYS updates also depend on POOL values */ > if (ring == TM_QW3_HV_PHYS) { > @@ -998,9 +1000,6 @@ static void xive2_tctx_set_cppr(XiveTCTX *tctx, uint8_t ring, uint8_t cppr) > } > } > > - /* PIPR should not be set to a value greater than CPPR */ > - regs[TM_PIPR] = (pipr_min > cppr) ? cppr : pipr_min; > - > rc = xive2_tctx_get_nvp_indexes(tctx, ring_min, &nvp_blk, &nvp_idx); > if (rc) { > qemu_log_mask(LOG_GUEST_ERROR, "XIVE: set CPPR on invalid context\n"); > @@ -1019,7 +1018,7 @@ static void xive2_tctx_set_cppr(XiveTCTX *tctx, uint8_t ring, uint8_t cppr) > > if (group_enabled && > lsmfb_min < cppr && > - lsmfb_min < regs[TM_PIPR]) { > + lsmfb_min < pipr_min) { > /* > * Thread has seen a group interrupt with a higher priority > * than the new cppr or pending local interrupt. Check the > @@ -1048,12 +1047,25 @@ static void xive2_tctx_set_cppr(XiveTCTX *tctx, uint8_t ring, uint8_t cppr) > nvp_blk, nvp_idx, > first_group, &group_level); > tctx->regs[ring_min + TM_LSMFB] = backlog_prio; > - if (backlog_prio != 0xFF) { > - xive2_presenter_backlog_decr(tctx->xptr, nvp_blk, nvp_idx, > - backlog_prio, group_level); > - regs[TM_PIPR] = backlog_prio; > + if (backlog_prio != lsmfb_min) { > + /* > + * If the group backlog scan finds a less favored or no interrupt, > + * then re-do the processing which may turn up a more favored > + * interrupt from IPB or the other pool. Backlog should not > + * find a priority < LSMFB. > + */ > + g_assert(backlog_prio >= lsmfb_min); > + goto again; > } > + > + xive2_presenter_backlog_decr(tctx->xptr, nvp_blk, nvp_idx, > + backlog_prio, group_level); > + pipr_min = backlog_prio; > } > + > + /* PIPR should not be set to a value greater than CPPR */ > + regs[TM_PIPR] = (pipr_min > cppr) ? cppr : pipr_min; > + > /* CPPR has changed, check if we need to raise a pending exception */ > xive_tctx_notify(tctx, ring_min, group_level); > }