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Date:   Mon, 27 Jun 2022 13:42:11 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
To:     Dave Hansen <dave.hansen@intel.com>
Cc:     Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>,
        Sean Christopherson <seanjc@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Joerg Roedel <jroedel@suse.de>,
        Ard Biesheuvel <ardb@kernel.org>,
        Andi Kleen <ak@linux.intel.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@linux.intel.com>,
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        Vlastimil Babka <vbabka@suse.cz>,
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        Thomas Gleixner <tglx@linutronix.de>,
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        Paolo Bonzini <pbonzini@redhat.com>,
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        Varad Gautam <varad.gautam@suse.com>,
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Subject: Re: [PATCHv7 14/14] x86/tdx: Add unaccepted memory support
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 <7c74e86e-295f-0958-cbdf-b54b4ca688dd@intel.com>
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On Fri, Jun 24, 2022 at 09:22:03AM -0700, Dave Hansen wrote:
> On 6/14/22 05:02, Kirill A. Shutemov wrote:
> >  static inline void __accept_memory(phys_addr_t start, phys_addr_t end)
> >  {
> >  	/* Platform-specific memory-acceptance call goes here */
> > -	error("Cannot accept memory");
> > +	if (is_tdx_guest())
> > +		tdx_accept_memory(start, end);
> > +	else
> > +		error("Cannot accept memory: unknown platform\n");
> >  }
> 
> There are quite a few of these
> 
> 	if (tdx())
> 		...
> 
> conditions in common code here.  Shouldn't this be something like a
> CC_ATTR_MEM_ACCEPT?
> 
> 	if (cc_platform_has(CC_ATTR_MEM_ACCEPT))
> 		cc_accept_memory(...);
> 	else
> 		error("Cannot accept memory: unknown platform\n");
> 
> I understand that TDX is the first one to the party.  Is this the time
> to add the cc_ infrastructure?

We need if tdx() check *somewhere* as how exactly memory gets accepted is
specific to a particular platform.

There are two callsites where memory acceptance happens. One of them is in
boot stub where we don't have cc_ infrastructure. So it will boil down to
a single cc_accept_memory() that will have 'if tdx()' inside.

I don't see much sense in the exercise. We can as well keep the 'if' in
accept_memory().

-- 
 Kirill A. Shutemov