2022-11-04 14:31:06

by Peter Gonda

Subject: [PATCH V2] KVM: SVM: Only dump VSMA to klog for debugging

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/[email protected]/
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 <[email protected]>
Reviewed-by: Sean Christopherson <[email protected]>
Cc: Jarkko Sakkinen <[email protected]>
Cc: Harald Hoyer <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: [email protected]
Cc: "H. Peter Anvin" <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
---
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

2022-11-07 16:07:25

by Jarkko Sakkinen

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/[email protected]/
> 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 <[email protected]>
> Reviewed-by: Sean Christopherson <[email protected]>
> Cc: Jarkko Sakkinen <[email protected]>
> Cc: Harald Hoyer <[email protected]>
> Cc: Paolo Bonzini <[email protected]>
> Cc: Thomas Gleixner <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: Borislav Petkov <[email protected]>
> Cc: Dave Hansen <[email protected]>
> Cc: [email protected]
> Cc: "H. Peter Anvin" <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> ---
> 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 <[email protected]>

BR, Jarkko

2022-11-07 18:16:32

by Paolo Bonzini

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/[email protected]/
> 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 <[email protected]>
> Reviewed-by: Sean Christopherson <[email protected]>
> Cc: Jarkko Sakkinen <[email protected]>
> Cc: Harald Hoyer <[email protected]>
> Cc: Paolo Bonzini <[email protected]>
> Cc: Thomas Gleixner <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: Borislav Petkov <[email protected]>
> Cc: Dave Hansen <[email protected]>
> Cc: [email protected]
> Cc: "H. Peter Anvin" <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> ---
> 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