linux-kernel - Re: [PATCH] phys_efi_set_virtual_address

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Date:	Wed, 20 Jun 2012 19:27:42 -0500
From:	Robin Holt <holt@....com>
To:	"H. Peter Anvin" <hpa@...ux.intel.com>
Cc:	Matthew Garrett <mjg59@...f.ucam.org>, Robin Holt <holt@....com>,
	linux-kernel@...r.kernel.org,
	"Sakkinen, Jarkko" <jarkko.sakkinen@...el.com>
Subject: Re: [PATCH] phys_efi_set_virtual_address_map needs va, no pa.

On Wed, Jun 20, 2012 at 01:41:54PM -0700, H. Peter Anvin wrote:
> On 06/20/2012 05:07 AM, Matthew Garrett wrote:
> > 
> > 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.
> > 
> 
> I think it is a bug, and with the trampoline work in 3.4 we should
> finally have a proper platform to fix it.
> 
> In particular, we should keep a full 1:1 page map around, and it should
> be the one that is in the trampoline (real_mode_header->trampoline_pgd)
> as we need the page directory to be 32-bit addressable.
> 
> The right thing to do is to sync the pgds in the 1:1 area, both for 64
> bit and for legacy 32 bit (PAE 32 bit don't need it, since all the
> kernel maps are shared.)  This is currently done ad hoc (and
> differently!) on both 32 and 64 bits and that really should be fixed.

What do you need from me?  If you want me to help with this, I have a
_WHOLE_ lot of learning to do.  Can you give me any pointers?

We are trying to get this finally fixed.  We have had work-around code
in SLES11 SP1, SLES11 SP2, and RHEL 6.x.  I would love to get this fixed
for future distro snaps.

Thanks,
Robin
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