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Date: Wed, 17 Aug 2016 15:01:51 +0800
From: Dave Young <dyoung@redhat.com>
To: Alex Thorlton <athorlton@sgi.com>
Cc: Borislav Petkov <bp@alien8.de>, Matt Fleming <matt@codeblueprint.co.uk>,
        linux-kernel@vger.kernel.org, Russ Anderson <rja@sgi.com>,
        Dimitri Sivanich <sivanich@sgi.com>, Mike Travis <travis@sgi.com>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org,
        linux-efi@vger.kernel.org
Subject: Re: [PATCH] Map in physical addresses in efi_map_region_fixed
Message-ID: <20160817070151.GC5498@dhcp-128-65.nay.redhat.com>
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> > Why do you guys need the physical mapping all of a sudden?
> 
> It's not that we need it all of the sudden, necessarily, it's just that
> we've had to make other changes to make things work with the new,
> (almost) completely isolated, EFI page tables.  We ended up choosing the
> lesser of two evils, and have decided to temporarily rely on the
> physical address of our runtime code, instead of continuing to rely on
> EFI_OLD_MEMMAP.

In efi_map_region, there is already mapped md->phys_addr for broken
firmware. SGI still need EFI_OLD_MEMMAP? I means in 1st kernel instead
of kexec kernel.

void __init efi_map_region(efi_memory_desc_t *md)
{
        unsigned long size = md->num_pages << PAGE_SHIFT;
        u64 pa = md->phys_addr;

        if (efi_enabled(EFI_OLD_MEMMAP))
                return old_map_region(md);

        /*
         * Make sure the 1:1 mappings are present as a catch-all for
         * b0rked
         * firmware which doesn't update all internal pointers after
         * switching
         * to virtual mode and would otherwise crap on us.
         */
        __map_region(md, md->phys_addr);

[snip]

Thanks
Dave