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From:   Ard Biesheuvel <ardb@kernel.org>
Date:   Fri, 12 May 2023 13:01:01 +0200
Message-ID: <CAMj1kXGmThuLGzKGG9pPNFaH_yKTZ_AnD5aNUd7qGG0=Enev4w@mail.gmail.com>
Subject: Re: [PATCHv10 04/11] efi/x86: Implement support for unaccepted memory
To:     "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc:     "Kirill A. Shutemov" <kirill@shutemov.name>,
        Borislav Petkov <bp@alien8.de>,
        Andy Lutomirski <luto@kernel.org>,
        Dave Hansen <dave.hansen@intel.com>,
        Sean Christopherson <seanjc@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Joerg Roedel <jroedel@suse.de>,
        Andi Kleen <ak@linux.intel.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@linux.intel.com>,
        David Rientjes <rientjes@google.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Peter Zijlstra <peterz@infradead.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Ingo Molnar <mingo@redhat.com>,
        Dario Faggioli <dfaggioli@suse.com>,
        Mike Rapoport <rppt@kernel.org>,
        David Hildenbrand <david@redhat.com>,
        Mel Gorman <mgorman@techsingularity.net>,
        marcelo.cerri@canonical.com, tim.gardner@canonical.com,
        khalid.elmously@canonical.com, philip.cox@canonical.com,
        aarcange@redhat.com, peterx@redhat.com, x86@kernel.org,
        linux-mm@kvack.org, linux-coco@lists.linux.dev,
        linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org
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On Fri, 12 May 2023 at 12:59, Kirill A. Shutemov
<kirill.shutemov@linux.intel.com> wrote:
>
> On Fri, May 12, 2023 at 09:39:30AM +0200, Ard Biesheuvel wrote:
> > Please replace PMD_SIZE with something along the lines of
> > EFI_UNACCEPTED_UNIT_SIZE and #define it to PMD_SIZE in
> > arch/x86/include/asm/efi.h.
> >
> > The comment below about the size of the bitmap vs the size of the
> > address space should probably move there as well.
>
> Okay, will do.
>
> > > +void accept_memory(phys_addr_t start, phys_addr_t end)
> > > +{
> > > +       unsigned long range_start, range_end;
> > > +       unsigned long bitmap_size;
> > > +       u64 unit_size;
> > > +
> > > +       if (!unaccepted_table)
> > > +               return;
> > > +
> > > +       unit_size = unaccepted_table->unit_size;
> > > +
> > > +       /*
> > > +        * Only care for the part of the range that is represented
> > > +        * in the bitmap.
> > > +        */
> > > +       if (start < unaccepted_table->phys_base)
> > > +               start = unaccepted_table->phys_base;
> > > +       if (end < unaccepted_table->phys_base)
> > > +               return;
> > > +
> > > +       /* Translate to offsets from the beginning of the bitmap */
> > > +       start -= unaccepted_table->phys_base;
> > > +       end -= unaccepted_table->phys_base;
> > > +
> > > +       /* Make sure not to overrun the bitmap */
> > > +       if (end > unaccepted_table->size * unit_size * BITS_PER_BYTE)
> > > +               end = unaccepted_table->size * unit_size * BITS_PER_BYTE;
> > > +
> >
> > Should we warn here?
>
> No. accept_memory() is nop for conventional memory (memblock calls it
> unconditionally).
>
> With the fixup, we only allocate bitmap for the range of physical address
> space where we have unaccepted memory. So if there's conventional memory
> after unaccepted, bitmap will not cover it.
>

Fair enough.