On Mon, 2012-10-22 at 11:43 -0400, Vivek Goyal wrote: > On Sat, Oct 20, 2012 at 08:06:23PM -0700, Eric W. Biederman wrote: > > [..] > > It is the non-pure UEFI case where non-UEFI table scans work. > > > > Of course it puzzles me why we can't find the table via scanning memory > > when running in a pure UEFI environment. Ah well that is a problem for > > another day. > > I have the same question. Why can we find acpi tables by scaning in > non-uefi case and why same is not possible in case of UEFI. I had sent an explanation out on Friday but looks like my email got stuck somewhere, and I don't see it on kexec list archive. On a UEFI machine with CSM, kernel finds RSDP by searching through EBDA. On a UEFI machine with no CSM, there is no EBDA I believe and kernel fails to find RSDP. Here is the message I see on a UEFI machine with no CSM: ACPI BIOS Bug: Error: A valid RSDP was not found (20120913/tbxfroot-219) -- Khalid
