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    SubjectRe: [RFC PATCH 0/5] x86/hw_breakpoint: protects more cpu entry data
    On Mon, May 25, 2020 at 11:27 PM Peter Zijlstra <peterz@infradead.org> wrote:
    >
    > On Mon, May 25, 2020 at 02:50:57PM +0000, Lai Jiangshan wrote:
    > > Hello
    > >
    > > The patchset is based on (tag: entry-v9-the-rest, tglx-devel/x86/entry).
    > > And it is complement of 3ea11ac991d
    > > ("x86/hw_breakpoint: Prevent data breakpoints on cpu_entry_area").
    > >
    > > After reading the code, we can see that more data needs to be protected
    > > against hw_breakpoint, otherwise it may cause
    > > dangerous/recursive/unwanted #DB.
    > >
    > >
    > > Lai Jiangshan (5):
    > > x86/hw_breakpoint: add within_area() to check data breakpoints
    > > x86/hw_breakpoint: Prevent data breakpoints on direct GDT
    > > x86/hw_breakpoint: Prevent data breakpoints on per_cpu cpu_tss_rw
    >
    > I think we can actually get rid of that #DB IST stack frobbing, also see
    > patches linked below.

    Hi, Peter

    I reviewed that patchset before. It is all what I want, but it still
    didn't remove IST-shifting. I remove it in V2.

    >
    > > x86/hw_breakpoint: Prevent data breakpoints on user_pcid_flush_mask
    >
    > Should we disallow the full structure just to be sure?

    Sure, just did it as you suggested, thanks!

    >
    > > x86/hw_breakpoint: Prevent data breakpoints on debug_idt_table
    >
    > That's going away, see:

    Yes, so I added a note in the patch, saying "Please drop this patch
    when Peter's work to remove debug_idt_table is merged."

    I directly drop the patch in V2.

    Thank you.
    Lai


    >
    > https://lkml.kernel.org/r/20200522204738.645043059@infradead.org
    >
    > But yes, nice!
    >

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