From: Matthew Garrett <mjg59@srcf.ucam.org>
To: Robin Holt <holt@sgi.com>
Cc: linux-kernel@vger.kernel.org, "H. Peter Anvin" <hpa@linux.intel.com>
Subject: Re: [PATCH] phys_efi_set_virtual_address_map needs va, no pa.
Date: Wed, 20 Jun 2012 13:07:02 +0100 [thread overview]
Message-ID: <20120620120702.GA3983@srcf.ucam.org> (raw)
In-Reply-To: <20120620082457.GE3464@sgi.com>
On Wed, Jun 20, 2012 at 03:24:57AM -0500, Robin Holt wrote:
> The kernel allocated memmap may end up being beyond the first
> 512GB of memory. That early range is identity mapped, while the
> remainder of memory is not. The net result is the memmap allocated by
> efi_enter_virtual_mode will not be accessible via its __pa as is currently
> passed back to EFI.
>
> Since EFI is going to have to parse the passed in table, I believe the
> EFI documentation is wrong.
>
> I asked one of our BIOS engineers to look at the Intel reference code
> and he said it was obvious that the address would have to be a virtaully
> accessible address as we are in virtual mode while EFI is handling the
> callback.
No, that's completely wrong. UEFI can't be called in virtual mode until
*after* SetVirtualAddressMap(). The UEFI spec indicates that all
physical memory must have an identity mapping at this stage (section
2.3.4), so if we don't then that's a bug that needs to be fixed.
--
Matthew Garrett | mjg59@srcf.ucam.org
next prev parent reply other threads:[~2012-06-20 12:07 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-20 8:24 [PATCH] phys_efi_set_virtual_address_map needs va, no pa Robin Holt
2012-06-20 12:07 ` Matthew Garrett [this message]
2012-06-20 20:41 ` H. Peter Anvin
2012-06-21 0:27 ` Robin Holt
2012-06-21 0:46 ` H. Peter Anvin
2012-06-21 16:52 ` Robin Holt
2012-06-22 0:35 ` H. Peter Anvin
2012-06-21 19:16 ` Konrad Rzeszutek Wilk
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