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    SubjectRe: [PATCH v2 2/4] x86/split_lock: Align x86_capability to unsigned long to avoid split locked access
    On Fri, Jun 29, 2018 at 01:48:45PM -0700, Dave Hansen wrote:
    > On 06/29/2018 01:38 PM, Fenghua Yu wrote:
    > > How to handle data that is used in generic code which can be used on
    > > non-Intel platform? For exmple, if I do this change for struct efi in
    > > include/linux/efi.h because set_bit() sets bits in efi.flags:
    > > - unsigned long flags;
    > > + unsigned long flags __aligned(unsigned long);
    > > } efi;
    > >
    > > People may argue that the alignment unnecessarily increases size of 'efi'
    > > on non-Intel platform which doesn't have split lock issue. Do we care this
    > > argument?
    >
    > Unaligned memory accesses are bad, pretty much universally. This is a
    > general good practice that we should have been doing anyway. Let folks
    > complain. Don't let it stop you.
    >
    > Also, look at the size of that structure. Look at how many pointers it
    > has. Do you think *anyone* is going to complain about an extra 4 bytes
    > in a 400-byte structure?
    >
    > > Another question, there will be a bunch of one-line changes for
    > > the alignment (i.e. adding __aligned(unsigned long)) in various files.
    > > Will the changes be put in one big patch or in separate one-liner patches?
    >
    > Just group them logically.

    Sure.

    Thanks.

    -Fenghua

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