From: Erwan Velu <e.velu@criteo.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>,
Erwan Velu <erwanaliasr1@gmail.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org, jmattson@google.com
Subject: Re: [PATCH] kvm: x86: Print "disabled by bios" only once per host
Date: Tue, 18 Feb 2020 17:28:49 +0100 [thread overview]
Message-ID: <70b4d8fa-57c0-055b-8391-4952dec32a58@criteo.com> (raw)
In-Reply-To: <20200214170508.GB20690@linux.intel.com>
On 14/02/2020 18:05, Sean Christopherson wrote:
> This has come up before[*]. Using _once() doesn't fully solve the issue
> when KVM is built as a module. The spam is more than likely a userspace
> bug, i.e. userspace is probing KVM on every CPU.
I made some progress on this.
That's "/usr/bin/udevadm trigger --type=devices --action=add" the culprit.
It does echo "add" in /sys/devices/system/cpu/cpu<x>/uevent
For the each cpu, it does the 'add' which trigger the "disabled by bios"
message from kvm_arch_init.
Note that doing a "add" on the same processor will trigger the same
message at every "add" event.
So I tried the patch of using pr_err_once() instead of printk() and the
behavior is fine : despite the number of "add" generated, there is a
single line being printed out.
Without the patch, every "add" generates the "disabled by bios" message.
So the question is : do we want to handle the case where a possible bios
missed the configuration of some cores ?
If no, then the patch is fine and could be submitted. I don't see the
need of printing this message at every call as it pollute the kernel log.
If yes, then we need to keep a trace of the number of enabled/disabled
cores so we can report a mismatch. As this message seems printed per
cpu, that would kind of mean a global variable right ?
What are your recommendations on this ?
Erwan,
next prev parent reply other threads:[~2020-02-18 16:30 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-14 14:30 [PATCH] kvm: x86: Print "disabled by bios" only once per host Erwan Velu
2020-02-14 17:05 ` Sean Christopherson
2020-02-18 16:28 ` Erwan Velu [this message]
2020-02-18 18:48 ` Sean Christopherson
2020-02-19 11:19 ` Erwan Velu
2020-02-19 11:32 ` Erwan Velu
2020-02-19 17:42 ` Erwan Velu
2020-02-19 16:18 ` Sean Christopherson
2020-02-19 16:53 ` Erwan Velu
2020-02-19 17:51 ` Paolo Bonzini
2020-02-19 21:52 ` Erwan Velu
2020-02-14 17:43 ` Jim Mattson
2020-02-27 18:00 ` [PATCH v2] kvm: x86: Limit the number of "kvm: disabled by bios" messages Erwan Velu
2020-02-28 10:37 ` Paolo Bonzini
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