Re: [PATCH] video:uvesafb: Fix oops that uvesafb try to execute NX-protected page

On Tue, Mar 27, 2012 at 02:32:43PM +0100, Alan Cox wrote:

On Tue, 27 Mar 2012 18:01:36 +0800
Wang YanQing [off-list ref] wrote:

quoted

Ok! I try to check pcibios_enabled first, but get some opposition by Alan Cox,
but I want to make thing work and fix the oops, so I choice the simple way to
check the (__supported_pte_mask & _PAGE_NX) instead of to check this variable plus
pci kernel boot parameter, pci mmconfig works or not, and more, and more. It is not
the best method, but it works and maybe all will feel happy.

Okay let me ask the obvious question - why is it not the best method ?

Apart from adding a helper in the includes for the arch code of

	static inline is_nx_enabled(void)
	{
		return !!(__supported_pte_mask & _PAGE_NX);
	}

is there anything else it lacks ?

Yes ideally we'd set the relevant ROM areas executable, but for a simple
fix is there anything else that's a problem with it ?

Ok! Maybe you had missed my previous reply
http://permalink.gmane.org/gmane.linux.kernel/1272433
It is not the best method, because the check is not enough.
I means when NX is actively, the pci bios is NX or not also depend on
the code path in pci_arch_init which will be influenced by the acpi on or off, pci kernel boot
parameter, even kernel config like pci access method PCI_GOANY, PCI_GOMMCONFIG, or PCI_GODIRECT,
but if I check the pcibios_enabled, all the above can be ignored.

if uvesafb use the PMI when PCI BIOS is X, it can get the better work efficience then use the redraw 
method as a fallback when do the panning.