| Message ID | 20221103210421.359837-1-pgonda@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: SVM: Only dump VSMA to klog for debugging | expand |
On Thu, Nov 03, 2022, Peter Gonda wrote: > The KERN_CONT documentation says it defaults back to KERNL_DEFAULT if the State what actually happens. Documentation is sometimes wrong, and just saying "the docs say XYZ" makes it sound like this is a fix based on code inspection, whereas you encountered a real problem. E.g. 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. > previous log line has a newline. So switch from KERN_CONT to > print_hex_dump_debug(). Jarkko pointed this out in the original submission, but the buggy patch got queued without the fixup. This is a good opportunity to throw in a link so that it's clear that the change is aligned with the original intent. Link: https://lore.kernel.org/all/YuPMeWX4uuR1Tz3M@kernel.org > Cc: Jarkko Sakkinen <jarkko@kernel.org> > Cc: Harald Hoyer <harald@profian.com> > Cc: Paolo Bonzini <pbonzini@redhat.com> > Cc: Sean Christopherson <seanjc@google.com> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Ingo Molnar <mingo@redhat.com> > Cc: Borislav Petkov <bp@alien8.de> > Cc: Dave Hansen <dave.hansen@linux.intel.com> > Cc: x86@kernel.org > Cc: "H. Peter Anvin" <hpa@zytor.com> > Cc: kvm@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > Signed-off-by: Peter Gonda <pgonda@google.com> > > Fixes: 6fac42f127b8 ("KVM: SVM: Dump Virtual Machine Save Area (VMSA) to klog") Fixes: usually goes before everything else, and this should probably Cc stable@ as well. With the above tweaks, Reviewed-by: Sean Christopherson <seanjc@google.com>
On Thu, Nov 3, 2022 at 4:25 PM Sean Christopherson <seanjc@google.com> wrote: > > On Thu, Nov 03, 2022, Peter Gonda wrote: > > The KERN_CONT documentation says it defaults back to KERNL_DEFAULT if the > > State what actually happens. Documentation is sometimes wrong, and just saying > "the docs say XYZ" makes it sound like this is a fix based on code inspection, > whereas you encountered a real problem. E.g. > > 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. > > > previous log line has a newline. So switch from KERN_CONT to > > print_hex_dump_debug(). > > Jarkko pointed this out in the original submission, but the buggy patch got queued > without the fixup. This is a good opportunity to throw in a link so that it's > clear that the change is aligned with the original intent. > > Link: https://lore.kernel.org/all/YuPMeWX4uuR1Tz3M@kernel.org Thanks. I've expanded on the description based on your feedback. > > > Cc: Jarkko Sakkinen <jarkko@kernel.org> > > Cc: Harald Hoyer <harald@profian.com> > > Cc: Paolo Bonzini <pbonzini@redhat.com> > > Cc: Sean Christopherson <seanjc@google.com> > > Cc: Thomas Gleixner <tglx@linutronix.de> > > Cc: Ingo Molnar <mingo@redhat.com> > > Cc: Borislav Petkov <bp@alien8.de> > > Cc: Dave Hansen <dave.hansen@linux.intel.com> > > Cc: x86@kernel.org > > Cc: "H. Peter Anvin" <hpa@zytor.com> > > Cc: kvm@vger.kernel.org > > Cc: linux-kernel@vger.kernel.org > > Signed-off-by: Peter Gonda <pgonda@google.com> > > > > Fixes: 6fac42f127b8 ("KVM: SVM: Dump Virtual Machine Save Area (VMSA) to klog") > > Fixes: usually goes before everything else, and this should probably Cc stable@ > as well. > > With the above tweaks, > > Reviewed-by: Sean Christopherson <seanjc@google.com> Done. Sent a V2 with your review tag.
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; }
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(). Cc: Jarkko Sakkinen <jarkko@kernel.org> Cc: Harald Hoyer <harald@profian.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Sean Christopherson <seanjc@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: x86@kernel.org Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Peter Gonda <pgonda@google.com> Fixes: 6fac42f127b8 ("KVM: SVM: Dump Virtual Machine Save Area (VMSA) to klog") --- Tested before without DEBUG or CONFIG_DYNAMIC_DEBUG I would see the VMSA raw hex bytes spew on dmesg. After change no such spew. --- arch/x86/kvm/svm/sev.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)