RE: [PATCH] remove pa->va->pa conversion for efi.acpi

From: David Mosberger <davidm_at_napali.hpl.hp.com>
Date: 2003-07-18 04:09:50
>>>>> On Thu, 17 Jul 2003 10:43:19 -0700, "Tolentino, Matthew E" <matthew.e.tolentino@intel.com> said:

  >> Does ACPI really guarantee that the table is never stored at physical
  >> address 0?  If not, then leaving it as a virtual address might be
  >> safer.  (Yes, I know it's very unlikely for today's system, but at
  >> least on ia64, pfn 0 is normal RAM so it seems at least in principle
  >> possible to store the ACPI table there).

  Matthew> No guarantee that I could find...I suppose this is
  Matthew> technically possible. :) However, considering the ACPI
  Matthew> routines expect a physical address and thus immediately map
  Matthew> it to get the descriptor (either directly with virt_to_phys
  Matthew> or via ioremap), this seems redundant.  Given the mapping
  Matthew> scheme employed, is this still risky?  I'd like to reuse
  Matthew> the same code path for ia32, but don't want to break ia64.

Note that I'm only pointing this out because I thought there were some
NULL-pointer checks.  If it's a physical address, 0 is a valid
address.  If it's an (identity-mapped) kernel address, NULL-pointer
checks are OK.

	--david
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Received on Thu Jul 17 14:10:12 2003

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