From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Mosberger Date: Thu, 17 Jul 2003 18:09:50 +0000 Subject: RE: [PATCH] remove pa->va->pa conversion for efi.acpi Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org >>>>> On Thu, 17 Jul 2003 10:43:19 -0700, "Tolentino, Matthew E" 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