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([163.239.22.29]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-3751dae6377sm12811395eec.3.2026.11.11.00.46.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 11 Nov 2026 00:46:04 -0800 (PST) From: Hyunjung Ko To: Madhavan Srinivasan , Vaibhav Jain Cc: Michael Ellerman , Nicholas Piggin , Athira Rajeev , Christophe Leroy , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Hyunjung Ko , stable@vger.kernel.org Subject: [PATCH] powerpc/kvm-hv-pmu: don't allocate under lock_l0_stats in kvmppc_init_hostwide Date: Wed, 11 Nov 2026 17:45:52 +0900 Message-ID: <20261111084553.3039506-1-hj351016@gmail.com> X-Mailer: git-send-email 2.43.0 X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , Precedence: list X-Archived-By: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 kvmppc_init_hostwide() builds the hostwide L0-stats guest-state message and buffer with kvmppc_gsm_new() and kvmppc_gsb_new() while holding lock_l0_stats, which is taken with spin_lock_irqsave(). Both helpers allocate with GFP_KERNEL (and kvmppc_gsb_new() does a further GFP_KERNEL allocation internally), so they can sleep in atomic context, triggering "BUG: sleeping function called from invalid context" under CONFIG_DEBUG_ATOMIC_SLEEP. lock_l0_stats is a spinlock because it also serializes the PMU ->read path (kvmppc_pmu_event_update()), so it cannot be turned into a mutex. Build the message and buffer in local variables outside the lock and only take the lock to publish them, rechecking for a concurrent registration. Fixes: f0c9c49c5067 ("powerpc/kvm-hv-pmu: Implement GSB message-ops for hostwide counters") Cc: stable@vger.kernel.org Signed-off-by: Hyunjung Ko --- arch/powerpc/perf/kvm-hv-pmu.c | 70 ++++++++++++++++++++++++++---------------- 1 file changed, 42 insertions(+), 28 deletions(-) diff --git a/arch/powerpc/perf/kvm-hv-pmu.c b/arch/powerpc/perf/kvm-hv-pmu.c index aa72b96b5a8c..deba59cbe234 100644 --- a/arch/powerpc/perf/kvm-hv-pmu.c +++ b/arch/powerpc/perf/kvm-hv-pmu.c @@ -314,53 +314,67 @@ static struct kvmppc_gs_msg_ops gsb_ops_l0_stats = { static int kvmppc_init_hostwide(void) { - int rc = 0; + struct kvmppc_gs_msg *gsm; + struct kvmppc_gs_buff *gsb; unsigned long flags; + int rc; spin_lock_irqsave(&lock_l0_stats, flags); - /* already registered ? */ if (gsm_l0_stats) { - rc = 0; - goto out; + spin_unlock_irqrestore(&lock_l0_stats, flags); + return 0; } + spin_unlock_irqrestore(&lock_l0_stats, flags); + + /* + * kvmppc_gsm_new() and kvmppc_gsb_new() allocate with GFP_KERNEL and + * may sleep, so build the message and buffer outside lock_l0_stats, + * which is a spinlock (it also serializes the PMU ->read path), and + * only take the lock to publish them. + */ /* setup the Guest state message/buffer to talk to L0 */ - gsm_l0_stats = kvmppc_gsm_new(&gsb_ops_l0_stats, &l0_stats, - GSM_SEND, GFP_KERNEL); - if (!gsm_l0_stats) { - rc = -ENOMEM; - goto out; - } + gsm = kvmppc_gsm_new(&gsb_ops_l0_stats, &l0_stats, GSM_SEND, GFP_KERNEL); + if (!gsm) + return -ENOMEM; /* Populate the Idents */ - kvmppc_gsm_include(gsm_l0_stats, KVMPPC_GSID_L0_GUEST_HEAP); - kvmppc_gsm_include(gsm_l0_stats, KVMPPC_GSID_L0_GUEST_HEAP_MAX); - kvmppc_gsm_include(gsm_l0_stats, KVMPPC_GSID_L0_GUEST_PGTABLE_SIZE); - kvmppc_gsm_include(gsm_l0_stats, KVMPPC_GSID_L0_GUEST_PGTABLE_SIZE_MAX); - kvmppc_gsm_include(gsm_l0_stats, KVMPPC_GSID_L0_GUEST_PGTABLE_RECLAIM); + kvmppc_gsm_include(gsm, KVMPPC_GSID_L0_GUEST_HEAP); + kvmppc_gsm_include(gsm, KVMPPC_GSID_L0_GUEST_HEAP_MAX); + kvmppc_gsm_include(gsm, KVMPPC_GSID_L0_GUEST_PGTABLE_SIZE); + kvmppc_gsm_include(gsm, KVMPPC_GSID_L0_GUEST_PGTABLE_SIZE_MAX); + kvmppc_gsm_include(gsm, KVMPPC_GSID_L0_GUEST_PGTABLE_RECLAIM); /* allocate GSB. Guest/Vcpu Id is ignored */ - gsb_l0_stats = kvmppc_gsb_new(kvmppc_gsm_size(gsm_l0_stats), 0, 0, - GFP_KERNEL); - if (!gsb_l0_stats) { + gsb = kvmppc_gsb_new(kvmppc_gsm_size(gsm), 0, 0, GFP_KERNEL); + if (!gsb) { rc = -ENOMEM; - goto out; + goto free_gsm; } /* ask the ops to fill in the info */ - rc = kvmppc_gsm_fill_info(gsm_l0_stats, gsb_l0_stats); + rc = kvmppc_gsm_fill_info(gsm, gsb); + if (rc) + goto free_gsb; -out: - if (rc) { - if (gsm_l0_stats) - kvmppc_gsm_free(gsm_l0_stats); - if (gsb_l0_stats) - kvmppc_gsb_free(gsb_l0_stats); - gsm_l0_stats = NULL; - gsb_l0_stats = NULL; + spin_lock_irqsave(&lock_l0_stats, flags); + if (gsm_l0_stats) { + /* raced with another CPU; use the existing registration */ + spin_unlock_irqrestore(&lock_l0_stats, flags); + rc = 0; + goto free_gsb; } + gsm_l0_stats = gsm; + gsb_l0_stats = gsb; spin_unlock_irqrestore(&lock_l0_stats, flags); + + return 0; + +free_gsb: + kvmppc_gsb_free(gsb); +free_gsm: + kvmppc_gsm_free(gsm); return rc; } -- 2.43.0