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Date: Sat, 4 Aug 2018 22:37:23 +0300
From: Konstantin Belousov <kostikbel@gmail.com>
To: Warner Losh <imp@bsdimp.com>
Cc: Emmanuel Vadot <manu@bidouilliste.com>, Ian Lepore <ian@freebsd.org>,
 Kyle Evans <kevans@freebsd.org>,
 freebsd-current Current <freebsd-current@freebsd.org>,
 Eitan Adler <eadler@freebsd.org>
Subject: Re: panic: mutex pmap not owned at ... efirt_machdep.c:255
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On Sat, Aug 04, 2018 at 08:28:25PM +0100, Warner Losh wrote:
> When I looked at it, I'd assumed there would be VA range we'd assign to the
> PAs in the EFI table that at the loader and kernel would agree on. The DMAP
> does this on x64 and aarch64, but that's not an option for armv7 nor i386.

It is not DMAP.

Amd64 works by assumption that ROM BIOS and its memory are located at
the physical addresses below 4G. Since kernel is always mapped at upper
half of the virtual address space, we hope that identity mapping for RT
memory can be established over the user half of the VA.

Apparently arm64 makes the same assumption.