linux-kernel - Re: [External] Re: [PATCH] RISC-V: add uniprocessor flush_tlb

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date: Mon, 29 Jan 2024 19:02:10 +0800
From: yunhui cui <cuiyunhui@...edance.com>
To: Jisheng Zhang <jszhang@...nel.org>
Cc: paul.walmsley@...ive.com, palmer@...belt.com, aou@...s.berkeley.edu, 
	alexghiti@...osinc.com, samuel.holland@...ive.com, ajones@...tanamicro.com, 
	mchitale@...tanamicro.com, dylan@...estech.com, 
	sergey.matyukevich@...tacore.com, prabhakar.mahadev-lad.rj@...renesas.com, 
	apatel@...tanamicro.com, linux-riscv@...ts.infradead.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [External] Re: [PATCH] RISC-V: add uniprocessor flush_tlb_range() support

Hi Jisheng,

On Mon, Jan 29, 2024 at 5:51 PM Jisheng Zhang <jszhang@...nel.org> wrote:
>
> On Mon, Jan 29, 2024 at 04:26:57PM +0800, yunhui cui wrote:
> > Hi Jisheng,
> >
> > On Mon, Jan 29, 2024 at 4:02 PM Jisheng Zhang <jszhang@...nel.org> wrote:
> > >
> > > On Thu, Jan 25, 2024 at 02:20:44PM +0800, Yunhui Cui wrote:
> > > > Add support for flush_tlb_range() to improve TLB performance for
> > > > UP systems. In order to avoid the mutual inclusion of tlbflush.h
> > > > and hugetlb.h, the UP part is also implemented in tlbflush.c.
> > >
> > > Hi Yunhui,
> > >
> > > IIRC, Samuel sent similar patch series a few weeks ago.
> > >
> > > https://lore.kernel.org/linux-riscv/20240102220134.3229156-1-samuel.holland@sifive.com/
> > >
> > > After that series, do you still need this patch?
> >
> > Thank you for your reminder. I didn't find it before I mailed my
> > patch. I just looked at the content of this patch. I understand that
> > my patch is needed. For a single core, a more concise TLB flush logic
> > is needed, and it is helpful to improve performance.
>
> Currently, riscv UP flush_tlb_range still use flush all TLB entries,
> obviously it's is a big hammer, this is what your patch is trying to
> optimize. I'm not sure whether I understand your code correctly or not.
> Let me know if I misunderstand your code.
>
> After patch5 of the Samuel's series, __flush_tlb_range is unified for
> SMP and UP, so that UP can also benefit from recent improvements, such
> as range flush rather than all.

In my opinion, UP does not need to combine some SMP if... else,
on_each_cpu(...) logic, which is also a manifestation of performance
improvement. what do you think?
Thanks,
Yunhui