linux-kernel - [PATCH] kvm: x86: Print "disabled by bios" only once per host

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Message-Id: <20200214143035.607115-1-e.velu@criteo.com>
Date:   Fri, 14 Feb 2020 15:30:35 +0100
From:   Erwan Velu <erwanaliasr1@...il.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     Erwan Velu <e.velu@...teo.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.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>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] kvm: x86: Print "disabled by bios" only once per host

The current behavior is to print a "disabled by bios" message per CPU thread.
As modern CPUs can have up to 64 cores, 128 on a dual socket, and turns this
printk to be a pretty noisy by showing up to 256 times the same line in a row.

This patch offer to only print the message once per host considering the BIOS will
disabled the feature for all sockets/cores at once and not on a per core basis.

Signed-off-by: Erwan Velu <e.velu@...teo.com>
---
 arch/x86/kvm/x86.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index fbabb2f06273..8f0d7a09d453 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7300,7 +7300,7 @@ int kvm_arch_init(void *opaque)
 		goto out;
 	}
 	if (ops->disabled_by_bios()) {
-		printk(KERN_ERR "kvm: disabled by bios\n");
+		printk_once(KERN_ERR "kvm: disabled by bios\n");
 		r = -EOPNOTSUPP;
 		goto out;
 	}
-- 
2.24.1