From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
To: Juergen Gross <jgross@suse.com>,
xen-devel@lists.xenproject.org, x86@kernel.org,
linux-kernel@vger.kernel.org
Cc: "Stefano Stabellini" <sstabellini@kernel.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Ingo Molnar" <mingo@redhat.com>,
"Borislav Petkov" <bp@alien8.de>,
"Dave Hansen" <dave.hansen@linux.intel.com>,
"H. Peter Anvin" <hpa@zytor.com>,
"Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>
Subject: Re: [PATCH v2] xen: fix is_xen_pmu()
Date: Fri, 25 Mar 2022 15:18:52 -0400 [thread overview]
Message-ID: <bc63e39f-33dd-0633-f72d-df08ece23684@oracle.com> (raw)
In-Reply-To: <20220325142002.31789-1-jgross@suse.com>
On 3/25/22 10:20 AM, Juergen Gross wrote:
> is_xen_pmu() is taking the cpu number as parameter, but it is not using
> it. Instead it just tests whether the Xen PMU initialization on the
> current cpu did succeed. As this test is done by checking a percpu
> pointer, preemption needs to be disabled in order to avoid switching
> the cpu while doing the test. While resuming from suspend() this seems
> not to be the case:
>
> [ 88.082751] ACPI: PM: Low-level resume complete
> [ 88.087933] ACPI: EC: EC started
> [ 88.091464] ACPI: PM: Restoring platform NVS memory
> [ 88.097166] xen_acpi_processor: Uploading Xen processor PM info
> [ 88.103850] Enabling non-boot CPUs ...
> [ 88.108128] installing Xen timer for CPU 1
> [ 88.112763] BUG: using smp_processor_id() in preemptible [00000000] code: systemd-sleep/7138
> [ 88.122256] caller is is_xen_pmu+0x12/0x30
> [ 88.126937] CPU: 0 PID: 7138 Comm: systemd-sleep Tainted: G W 5.16.13-2.fc32.qubes.x86_64 #1
> [ 88.137939] Hardware name: Star Labs StarBook/StarBook, BIOS 7.97 03/21/2022
> [ 88.145930] Call Trace:
> [ 88.148757] <TASK>
> [ 88.151193] dump_stack_lvl+0x48/0x5e
> [ 88.155381] check_preemption_disabled+0xde/0xe0
> [ 88.160641] is_xen_pmu+0x12/0x30
> [ 88.164441] xen_smp_intr_init_pv+0x75/0x100
>
> Fix that by replacing is_xen_pmu() by a simple boolean variable which
> reflects the Xen PMU initialization state on cpu 0.
>
> Modify xen_pmu_init() to return early in case it is being called for a
> cpu other than cpu 0 and the boolean variable not being set.
>
> Fixes: bf6dfb154d93 ("xen/PMU: PMU emulation code")
> Reported-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
> Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
next prev parent reply other threads:[~2022-03-25 19:39 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-25 14:20 [PATCH v2] xen: fix is_xen_pmu() Juergen Gross
2022-03-25 19:18 ` Boris Ostrovsky [this message]
2022-03-26 15:09 ` Boris Ostrovsky
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