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

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Date:   Mon, 7 Nov 2022 17:47:57 +0200
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Peter Gonda <pgonda@...gle.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Harald Hoyer <harald@...fian.com>,
        Paolo Bonzini <pbonzini@...hat.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 Fri, Nov 04, 2022 at 07:22:20AM -0700, 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;
>  }
> -- 
> 2.38.1.431.g37b22c650d-goog
> 

OK, this was my careless mistake, sorry about that:


Acked-by: Jarkko Sakkinen <jarkko@...nel.org>

BR, Jarkko