linux-kernel - Re: [PATCH V2] KVM: SVM: Only dump VSMA to klog for debugging

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Message-ID: <e13afbf9-f4ed-10c1-cf78-bd634c554d4d@redhat.com>
Date:   Mon, 7 Nov 2022 18:18:21 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Peter Gonda <pgonda@...gle.com>, jarkko@...nel.org
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Harald Hoyer <harald@...fian.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH V2] KVM: SVM: Only dump VSMA to klog for debugging

On 11/4/22 15:22, Peter Gonda wrote:
> Explicitly print the VMSA dump at KERN_DEBUG log level, KERN_CONT uses
> KERNEL_DEFAULT if the previous log line has a newline, i.e. if there's
> nothing to continuing, and as a result the VMSA gets dumped when it
> shouldn't.
> 
> The KERN_CONT documentation says it defaults back to KERNL_DEFAULT if the
> previous log line has a newline. So switch from KERN_CONT to
> print_hex_dump_debug().
> 
> Jarkko pointed this out in reference to the original patch. See:
> https://lore.kernel.org/all/YuPMeWX4uuR1Tz3M@kernel.org/
> print_hex_dump(KERN_DEBUG, ...) was pointed out there, but
> print_hex_dump_debug() should similar.
> 
> Fixes: 6fac42f127b8 ("KVM: SVM: Dump Virtual Machine Save Area (VMSA) to klog")
> Signed-off-by: Peter Gonda <pgonda@...gle.com>
> Reviewed-by: Sean Christopherson <seanjc@...gle.com>
> Cc: Jarkko Sakkinen <jarkko@...nel.org>
> Cc: Harald Hoyer <harald@...fian.com>
> Cc: Paolo Bonzini <pbonzini@...hat.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> Cc: x86@...nel.org
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: kvm@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> Cc: stable@...r.kernel.org
> ---
>   arch/x86/kvm/svm/sev.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index c0c9ed5e279cb..9b8db157cf773 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -605,7 +605,7 @@ static int sev_es_sync_vmsa(struct vcpu_svm *svm)
>   	save->dr6  = svm->vcpu.arch.dr6;
>   
>   	pr_debug("Virtual Machine Save Area (VMSA):\n");
> -	print_hex_dump(KERN_CONT, "", DUMP_PREFIX_NONE, 16, 1, save, sizeof(*save), false);
> +	print_hex_dump_debug("", DUMP_PREFIX_NONE, 16, 1, save, sizeof(*save), false);
>   
>   	return 0;
>   }

Queued, thanks.

Paolo