Re: [RFC PATCH v1 09/28] x86/efi: Access EFI data as encrypted when SEV is active

From	Borislav Petkov <bp@suse.de>
Newsgroups	linux.kernel
Subject	Re: [RFC PATCH v1 09/28] x86/efi: Access EFI data as encrypted when SEV is active
Date	2016-09-22 22:20 +0200
Message-ID	<skiDn-2wz-1@gated-at.bofh.it> (permalink)
References	(5 earlier) <skdNn-7ZV-15@gated-at.bofh.it> <skfFv-Hc-9@gated-at.bofh.it> <skhHk-1Xw-5@gated-at.bofh.it> <skhHk-1Xw-3@gated-at.bofh.it> <skiDn-2wz-3@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Thu, Sep 22, 2016 at 02:49:22PM -0500, Tom Lendacky wrote:
> > I thought that reduction is the reservation of bits for the SME mask.
> > 
> > What other reduction is there?
> 
> There is a reduction in physical address space for the SME mask and the
> bits used to aid in identifying the ASID associated with the memory
> request. This allows for the memory controller to determine the key to
> be used for the encryption operation (host/hypervisor key vs. an SEV
> guest key).

Ok, I think I see what you mean: you call SME mask the bit in CPUID
Fn8000_001F[EBX][5:0], i.e., the C-bit, i.e. sme_me_mask. And the other
reduction is the key ASID, i.e., CPUID Fn8000_001F[EBX][11:6], i.e.
sme_me_loss.

I think we're on the same page - I was simply calling everything SME
mask because both are together in the PTE:

"Additionally, in some implementations, the physical address size of the
processor may be reduced when memory encryption features are enabled,
for example from 48 to 43 bits."

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--

Thread

Re: [RFC PATCH v1 09/28] x86/efi: Access EFI data as encrypted when  SEV is active Borislav Petkov <bp@suse.de> - 2016-09-22 16:40 +0200
  Re: [RFC PATCH v1 09/28] x86/efi: Access EFI data as encrypted when  SEV is active Paolo Bonzini <pbonzini@redhat.com> - 2016-09-22 16:50 +0200
    Re: [RFC PATCH v1 09/28] x86/efi: Access EFI data as encrypted when  SEV is active Paolo Bonzini <pbonzini@redhat.com> - 2016-09-22 17:10 +0200
      Re: [RFC PATCH v1 09/28] x86/efi: Access EFI data as encrypted when  SEV is active Paolo Bonzini <pbonzini@redhat.com> - 2016-09-22 19:10 +0200
        Re: [RFC PATCH v1 09/28] x86/efi: Access EFI data as encrypted when  SEV is active Borislav Petkov <bp@suse.de> - 2016-09-22 19:30 +0200
      Re: [RFC PATCH v1 09/28] x86/efi: Access EFI data as encrypted when  SEV is active Borislav Petkov <bp@suse.de> - 2016-09-22 19:10 +0200
        Re: [RFC PATCH v1 09/28] x86/efi: Access EFI data as encrypted when  SEV is active Borislav Petkov <bp@suse.de> - 2016-09-22 21:20 +0200
          Re: [RFC PATCH v1 09/28] x86/efi: Access EFI data as encrypted when  SEV is active Borislav Petkov <bp@suse.de> - 2016-09-22 22:20 +0200
    Re: [RFC PATCH v1 09/28] x86/efi: Access EFI data as encrypted when  SEV is active Borislav Petkov <bp@suse.de> - 2016-09-22 17:10 +0200
    Re: [RFC PATCH v1 09/28] x86/efi: Access EFI data as encrypted when  SEV is active Paolo Bonzini <pbonzini@redhat.com> - 2016-09-22 21:00 +0200
  Re: [RFC PATCH v1 09/28] x86/efi: Access EFI data as encrypted when  SEV is active Paolo Bonzini <pbonzini@redhat.com> - 2016-09-22 20:30 +0200
    Re: [RFC PATCH v1 09/28] x86/efi: Access EFI data as encrypted when  SEV is active Borislav Petkov <bp@suse.de> - 2016-09-22 20:40 +0200
      Re: [RFC PATCH v1 09/28] x86/efi: Access EFI data as encrypted when  SEV is active Kai Huang <kaih.linux@gmail.com> - 2016-09-23 11:40 +0200
        Re: [RFC PATCH v1 09/28] x86/efi: Access EFI data as encrypted when  SEV is active Borislav Petkov <bp@suse.de> - 2016-09-23 12:00 +0200

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