On 2014/2/28 13:56, Matthew Garrett wrote: > On Fri, Feb 28, 2014 at 01:22:37PM +0800, Li, Aubrey wrote: >> On 2014/2/28 12:56, Matthew Garrett wrote: >>> EFI reboot is still somewhat unreliable - it may be safe after the >>> recent patches to provide a 1:1 mapping. >> >> So it's acceptable to put EFI in the default list. > > Probably, once we've got those patches landed (I've lost track of > whether they're in 3.13 or aimed at 3.14)
You didn't look the reference I quoted in the patch. It's stable if 32/64 bit linux call the corresponding 32/64bit EFI runtime service. Matt Fleming's mixed mode is aiming at 3.15: http://git.kernel.org/cgit/linux/kernel/git/mfleming/efi.git/log/?h=mixed-mode > >>> CF9 is, as far as I know, not part of any spec, so it seems like a bad >>> idea to put it in the default list. >> >> Any hurt known if put it in the default list? > > Mm. Not all x86 platforms support cf8/cf9 (Moorestown, for instance) and > so it's theoretically possible that they'd put some different hardware > there instead. But then, Moorestown probably has its own reboot code, so > that may not matter? Yes, Moorestown has its own machine_ops. Instead of the system hanging after issue "reboot" command, I think and suggest CF9 is worth to have a try. > >>> >>> What do the ACPI reboot vectors look like on these systems? >> >> Reset register address: 0xCF9 >> Value to cause reset: 0x6 > > Huh. But that's almost exactly what the PCI reboot code would do. Why > does the PCI method work but the ACPI one fail? Does it really depend on > ORing the original value with the reset value? Or is the timing just > somehow marginal? reboot returns at: if (!(acpi_gbl_FADT.flags & ACPI_FADT_RESET_REGISTER)) return; This is a ACPI bug or intention, who knows. > >>> This is definitely incorrect. The ACPI write *must* occur twice in order >>> to be effective on various systems. EFI shouldn't be attempted until >>> after the second ACPI write. >>> >> >> Do we have any spec mentioned that? > > Nope. This is entirely unspecified, it's just how things work - several > vendors use cf9 for the ACPI reboot vector, and there have to be two > writes to cf9 to trigger the reboot. Windows attempts the write twice, > and as a result things work. > Thanks to clarify this, I'll refine the patch, including CF9 if you don't have more concern. -Aubrey -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
