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    SubjectRe: [RFC PATCH 00/16] PTI support for x86-32
    Hi Linus,

    On Tue, Jan 16, 2018 at 10:59:01AM -0800, Linus Torvalds wrote:
    > Yes, I'm very happy to see that this is actually not nearly as bad as
    > I feared it might be,

    Yeah, I was looking at the original PTI patches and my impression was
    that a lot of the complicated stuff (like setting up the cpu_entry_area)
    was already in there for 32 bit too. So it was mostly about the entry
    code and some changes to the 32bit page-table code.

    > Some of those #ifdef's in the PTI code you added might want more
    > commentary about what the exact differences are. And maybe they could
    > be done more cleanly with some abstraction. But nothing looked
    > _horrible_.

    I'll add more comments and better abstraction, Dave has already
    suggested some improvements here. Reading some of my comments again,
    they need a rework anyway.

    > .. and please run all the segment and syscall selfchecks that Andy has written.

    Didn't know about them yet, thanks. I will run them too in my testing

    > Xen PV and PTI don't work together even on x86-64 afaik, the Xen
    > people apparently felt it wasn't worth it. See the
    >
    > if (hypervisor_is_type(X86_HYPER_XEN_PV)) {
    > pti_print_if_insecure("disabled on XEN PV.");
    > return;
    > }
    >
    > in pti_check_boottime_disable().

    But I might have broken something for them anyway, honestly I didn't pay
    much attention to the XEN_PV case as I was trying to get it running
    here. My hope is that someone who knows Xen better than I do will help
    out :)


    Regards,

    Joerg

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