linux-kernel - Re: [PATCH] KVM: Only display message about bios support disabled once

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Message-ID: <3193bafc-9dbf-67ca-beca-8066765b2339@amd.com>
Date:   Tue, 31 May 2022 20:57:01 -0500
From:   Mario Limonciello <mario.limonciello@....com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        "open list:KERNEL VIRTUAL MACHINE FOR X86 (KVM/x86)" 
        <kvm@...r.kernel.org>,
        "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" 
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] KVM: Only display message about bios support disabled
 once

On 5/27/22 11:08, Sean Christopherson wrote:
> On Thu, May 26, 2022, Mario Limonciello wrote:
>> On an OEM laptop I see the following message 10 times in my dmesg:
>> "kvm: support for 'kvm_amd' disabled by bios"
>>
>> This might be useful the first time, but there really isn't a point
>> to showing the error 9 more times.  The BIOS still has it disabled.
>> Change the message to only display one time.
> 
> NAK, this has been discussed multiple times in the past[1][2], there are edge cases
> where logging multiple messages is desirable.  Even using a ratelimited printk is
> essentially a workaround for a systemd bug[3], which I'm guessing is the cuplrit here.
> 
> [1] https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Fall%2F20190826182320.9089-1-tony.luck%40intel.com&amp;data=05%7C01%7Cmario.limonciello%40amd.com%7C2e1eed66ff8a412cec0508da3ffb1c1b%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637892645000687319%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&amp;sdata=X3Hs2QwXLsgAEEQkP7WMniywwoCn065sVh8DFagYzLE%3D&amp;reserved=0
> [2] https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Fall%2F20200214143035.607115-1-e.velu%40criteo.com&amp;data=05%7C01%7Cmario.limonciello%40amd.com%7C2e1eed66ff8a412cec0508da3ffb1c1b%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637892645000687319%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&amp;sdata=EMe2b9Mu7Pc9Z%2FcBmTPZaChUaDlQD%2FKGwK%2BYM%2Fd1VUY%3D&amp;reserved=0
> [3] https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fsystemd%2Fsystemd%2Fissues%2F14906&amp;data=05%7C01%7Cmario.limonciello%40amd.com%7C2e1eed66ff8a412cec0508da3ffb1c1b%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637892645000687319%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&amp;sdata=8fMPC1Opl85BmqqoPJ4ASI6Y58h%2BuTM5oFDS76bqPv0%3D&amp;reserved=0

Sean,

Appreciate the pointer at those earlier threads and the userspace issue.

Yes; it's certainly caused by systemd.  I can reproduce another 10 
entries just like the last link via `udevadm trigger --type=devices 
--action=add`.  I'm on a more modern version of systemd (249.11) so even 
though it was claimed to be fixed previously it resurfaced.  I'll leave 
a comment with systemd accordingly.

Thanks,