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Date:   Thu, 30 May 2019 03:55:11 +0000
From:   "Edgecombe, Rick P" <>
To:     "" <>,
        "" <>,
        "" <>,
        "" <>,
        "" <>
CC:     "" <>,
        "" <>,
        "" <>,
        "" <>,
        "" <>,
        "" <>,
        "" <>,
        "" <>,
        "Hansen, Dave" <>
Subject: Re: [PATCH] vmalloc: Don't use flush flag when no exec perm

On Tue, 2019-05-28 at 22:51 -0700, Rick Edgecombe wrote:
> The addition of VM_FLUSH_RESET_PERMS for BPF JIT allocations was
> bisected to prevent boot on an UltraSparc III machine. It was found
> that
> sometime shortly after the TLB flush this flag does on vfree of the
> program, the machine hung. Further investigation showed that before
> any of
> the changes for this flag were introduced, with
> configured (which does a similar TLB flush of the vmalloc range on
> every vfree), this machine also hung shortly after the first vmalloc
> unmap/free.
> So the evidence points to there being some existing issue with the
> vmalloc TLB flushes, but it's still unknown exactly why these hangs
> are
> happening on sparc. It is also unknown when someone with this
> hardware
> could resolve this, and in the meantime using this flag on it turns a
> lurking behavior into something that prevents boot.

The sparc TLB flush issue has been bisected and is being worked on now,
so hopefully we won't need this patch:

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