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    SubjectRe: [stable] [113/197] x86, cacheinfo: Calculate L3 indices
    On Thu, May 06, 2010 at 04:13:58PM +0200, Borislav Petkov wrote:
    > From: Jiri Kosina <jkosina@suse.cz>
    > Date: Thu, May 06, 2010 at 09:46:21AM -0400
    >
    > > Well, we have
    > >
    > > #ifdef CONFIG_K8_NB
    > > static inline struct pci_dev *node_to_k8_nb_misc(int node)
    > > {
    > > return (node < num_k8_northbridges) ? k8_northbridges[node] : NULL;
    > > }
    > > #else
    > > static inline struct pci_dev *node_to_k8_nb_misc(int node)
    > > {
    > > return NULL;
    > > }
    > > #endif
    > >
    > > So it legitimately returns NULL in two cases:
    > >
    > > 1) if someone passes too large node
    > > 2) if CONFIG_K8_NB is unset
    > >
    > > 1) Either we assume that node will always be in the range (i.e.
    > > amd_get_nb_id() will never go crazy return anything bogus), and then we
    > > could just drop the test completely. Or we want to check for such the
    > > possibility, and then node_to_k8_nb_misc() is going to return NULL in such
    > > cases, and so we want to check for it.
    >
    > No, we want to check it since K8_NB has many users - not only L3.
    >
    > > 2) is now moot, as all three in-tree callers are now under proper ifdefs
    > > (CONFIG_CPU_SUP_AMD, which depends on CONFIG_K8_NB after your patch has
    > > been applied). So I believe we could remove it, right?
    >
    > I don't think I understand "remove it" here. Which "it" you're referring to?
    >
    > > Either way, current state seems inconsistent. So either we should add the
    > > return value check to amd_calc_l3_indices() as well, or remove all the
    > > NULL magic altogether, i.e. the (untested) patch below.
    > >
    > > What do you think?
    >
    > Take a look at
    >
    > http://git.kernel.org/?p=linux/kernel/git/x86/linux-2.6-tip.git;a=commitdiff;h=f2b20e41407fccfcfacf927ff91ec888832a37af
    >
    > This does
    >
    > + if (num_k8_northbridges == 0)
    > + return;
    >
    > in amd_check_l3_disable().
    >
    > So if K8_NB has failed initializing for some reason, we never go near
    > the pci devs and the node_to_k8_nb_misc() calls since we effectively
    > disable the L3 functionality.
    >
    > Thus the NULL pointer checks you remove in the patch below are
    > superfluous, I agree, and I have already removed those in my tree along
    > with the other improvements/fixes I'm working on right now.

    So, was there ever a patch applied that fixed the bug that Jiri found in
    the stable kernels with this original patch that I could apply?

    thanks,

    greg k-h


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