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    SubjectRe: [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 <udknight@gmail.com> wrote:
    >
    > >
    > > 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.


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