linux-kernel - Re: [PATCH 05/17] asm-generic/tlb: Rename HAVE_RCU_TABLE_NO

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Date:   Mon, 16 Dec 2019 14:20:04 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>
Cc:     Will Deacon <will@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Nick Piggin <npiggin@...il.com>, linux-arch@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>,
        "David S. Miller" <davem@...emloft.net>,
        Helge Deller <deller@....de>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Paul Burton <paulburton@...nel.org>,
        Tony Luck <tony.luck@...el.com>,
        Richard Henderson <rth@...ddle.net>,
        Nick Hu <nickhu@...estech.com>,
        Paul Walmsley <paul.walmsley@...ive.com>
Subject: Re: [PATCH 05/17] asm-generic/tlb: Rename
 HAVE_RCU_TABLE_NO_INVALIDATE

On Mon, Dec 16, 2019 at 06:43:53PM +0530, Aneesh Kumar K.V wrote:
> On 12/16/19 6:07 PM, Peter Zijlstra wrote:

> > I'm confused, are you saing you're happy to have PowerPC eat the extra
> > TLB invalidates? I thought you cared about PPC performance :-)
> > 
> > 
> 
> Instead can we do
> 
> static inline void tlb_table_invalidate(struct mmu_gather *tlb)
> {
> #ifndef CONFIG_MMU_GATHER_RCU_TABLE_FREE
> 	 * Invalidate page-table caches used by hardware walkers. Then we still
> 	 * need to RCU-sched wait while freeing the pages because software
> 	 * walkers can still be in-flight.
> 	 */
> 	tlb_flush_mmu_tlbonly(tlb);
> #endif
> }

How does that not break ARM/ARM64/s390 and x86 ?