Re: [PATCH v8 1/2] x86/mm: add .bss..decrypted section to hold shared variables

From: Thomas Gleixner <tglx@linutronix.de>
To: Tom Lendacky <thomas.lendacky@amd.com>
Cc: "Borislav Petkov" <bp@suse.de>,
	"Brijesh Singh" <brijesh.singh@amd.com>,
	x86@kernel.org, linux-kernel@vger.kernel.org,
	kvm@vger.kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Sean Christopherson" <sean.j.christopherson@intel.com>,
	"Radim Krčmář" <rkrcmar@redhat.com>
Subject: Re: [PATCH v8 1/2] x86/mm: add .bss..decrypted section to hold shared variables
Date: Fri, 14 Sep 2018 16:55:51 +0200 (CEST)	[thread overview]
Message-ID: <alpine.DEB.2.21.1809141655030.10480@nanos.tec.linutronix.de> (raw)
In-Reply-To: <07c76a33-7883-f407-5b1c-b6de7dda37b1@amd.com>

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On Fri, 14 Sep 2018, Tom Lendacky wrote:

> On 09/14/2018 09:12 AM, Borislav Petkov wrote:
> > On Fri, Sep 14, 2018 at 02:17:05PM +0200, Thomas Gleixner wrote:
> >>> The sme_encrypt_kernel() does not have access to pmd (after pointer
> >>> fixup is applied). You can extend the sme_encrypt_kernel() to pass an
> >>> additional arguments but then we start getting in include hell. The pmd
> >>> is defined as "pmdval_t". If we extend the sme_encrypt_kernel() then 
> >>> asm/mem_encrypt.h need to include the header file which defines
> >>> "pmdval_t". Adding the 'asm/pgtable_type.h' was causing all kind of
> >>> compilation errors. I didn't spend much time on it. IMO, we really don't
> >>> need to go in this path unless we see some value from doing this.
> >>
> >> Keep it here then.
> > 
> > *For what is worth*, a simple forward declaration works. I've taken the
> > 64-bit forward declaration of pmdval_t as SME is 64-bit only anyway.
> 
> Just my 2 cents, but I'd prefer it to be in head64.c.  This is where
> the future pagetable entries are all updated to set the encryption
> mask by applying sme_get_me_mask() to load_delta.  So, to me, it makes
> sense to keep the clearing of the encryption mask for the bss_decrypted
> section here.

Yes, at least for now, I just keep it there and we can sort that out after
we fixed the problem at hand.

Thanks,

	tglx