linux-kernel - Re: [PATCH v5 18/23] bpf: Use vmalloc special flag

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Message-ID: <1738e24239cc0c001245fdd4bd3811175c573ce2.camel@intel.com>
Date: Tue, 12 Aug 2025 18:03:11 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
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Subject: Re: [PATCH v5 18/23] bpf: Use vmalloc special flag

On Tue, 2025-08-12 at 18:43 +0200, John Paul Adrian Glaubitz wrote:
> I suspect that the main issue is to be found in the following patch which introduced VM_FLUSH_RESET_PERMS
> which may not work as expected on sun4u SPARC systems:

I think the problem we found with VM_FLUSH_RESET_PERMS was that the sparc64
kernel TLB flush implementation was broken. Since VM_FLUSH_RESET_PERMS caused
kernel TLB flushes to happen sooner, it just showed up sooner. [0] 

This other issue seems to be about userspace memory. So I wonder if these are
two separate issues? Bisecting to the original VM_FLUSH_RESET_PERMS would have
had the known sparc kernel range TLB flush issue. So to bisect the other issue
you might need to apply this [1].



[0] https://marc.info/?l=linux-sparc&m=155915694304118&w=2
[1] https://lore.kernel.org/all/57385AAB-C9A1-46AD-B743-445D4ECCA902@jrtc27.com/