From: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
To: Gautam Menghani <gautam@linux.ibm.com>,
maddy@linux.ibm.com, npiggin@gmail.com, mpe@ellerman.id.au,
chleroy@kernel.org, sshegde@linux.ibm.com,
amachhiw@linux.ibm.com
Cc: linuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH v3 4/4] KVM: PPC: Book3S HV: Take SRCU read lock around kvmppc_h_page_init() call
Date: Tue, 13 Oct 2026 20:01:51 +0530 [thread overview]
Message-ID: <y0c1r7s8.ritesh.list@gmail.com> (raw)
In-Reply-To: <20261012082922.218799-5-gautam@linux.ibm.com>
Gautam Menghani <gautam@linux.ibm.com> writes:
> Since there is no srcu read lock around kvmppc_h_page_init(), a
> "suspicious rcu_dereference_check() usage" can be triggered by running
> host linux with CONFIG_PROVE_RCU=y and the following code in the guest:
>
> plpar_hcall_norets(H_PAGE_INIT, H_ZERO_PAGE, phys_addr, 0);
>
> =============================
> WARNING: suspicious RCU usage
> 7.0.0-dirty #227 Not tainted
> -----------------------------
> ./include/linux/kvm_host.h:1074 suspicious rcu_dereference_check() usage!
>
> other info that might help us debug this:
>
> rcu_scheduler_active = 2, debug_locks = 1
> 1 lock held by qemu-system-ppc/2093:
> #0: c000000354197ab0 (&vcpu->mutex){+.+.}-{3:3}, at: kvm_vcpu_ioctl+0x10c/0xaf0
>
> stack backtrace:
> CPU: 30 UID: 0 PID: 2093 Comm: qemu-system-ppc Not tainted 7.0.0-dirty #227 PREEMPT(full)
> Hardware name: IBM,9080-HEX POWER10 (architected) 0x800200 0xf000006 of:IBM,FW1060.60 (NH1060_158) hv:phyp pSeries
> Call Trace:
> [c00000033e1bf430] [c000000001b3dbd4] dump_stack_lvl+0xc8/0x130 (unreliable)
> [c00000033e1bf470] [c0000000003da964] lockdep_rcu_suspicious+0x1f4/0x290
> [c00000033e1bf520] [c000000000231424] gfn_to_memslot+0x1b4/0x1c0
> [c00000033e1bf560] [c00000000023637c] kvm_clear_guest+0x9c/0x110
> [c00000033e1bf5c0] [c0000000002714a4] kvmppc_h_page_init+0x160/0x1a0
> [c00000033e1bf610] [c00000000026c040] kvmppc_pseries_do_hcall+0x1930/0x1940
> [c00000033e1bf6d0] [c00000000026fb18] kvmppc_vcpu_run_hv+0x268/0x800
> [c00000033e1bf7a0] [c000000000246b30] kvmppc_vcpu_run+0x30/0x50
> [c00000033e1bf7c0] [c000000000241ed4] kvm_arch_vcpu_ioctl_run+0x364/0x530
> [c00000033e1bf860] [c00000000022b870] kvm_vcpu_ioctl+0x1b0/0xaf0
> [c00000033e1bfa50] [c0000000009b4514] sys_ioctl+0x144/0x190
> [c00000033e1bfab0] [c000000000034330] system_call_exception+0x170/0x370
> [c00000033e1bfe50] [c00000000000d05c] system_call_vectored_common+0x15c/0x2ec
>
> Fix this by taking a srcu read lock around kvmppc_h_page_init().
Looks good to me. Please feel free to add:
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
prev parent reply other threads:[~2026-10-13 14:33 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-12 8:29 [PATCH v3 0/4] Fixes for KVM HV around synchronization and initializations Gautam Menghani
2026-10-12 8:29 ` [PATCH v3 1/4] KVM: PPC: Book3S HV: Ensure that calls to idr_alloc are synchronized Gautam Menghani
2026-10-12 8:29 ` [PATCH v3 2/4] KVM: PPC: Book3S HV: XICS: Update irq_type for cleanup to work Gautam Menghani
2026-10-12 8:29 ` [PATCH v3 3/4] KVM: PPC: Book3S HV: XICS: Avoid NULL ptr deref in kvmppc_xive_cleanup_vcpu() Gautam Menghani
2026-10-12 8:29 ` [PATCH v3 4/4] KVM: PPC: Book3S HV: Take SRCU read lock around kvmppc_h_page_init() call Gautam Menghani
2026-10-13 14:31 ` Ritesh Harjani [this message]
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