Date:   Sun, 19 Mar 2023 19:45:36 +0100
From:   Thomas Bogendoerfer <tsbogend@alpha.franken.de>
To:     Matthew Wilcox <willy@infradead.org>
Cc:     linux-arch@vger.kernel.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org
Subject: Re: [PATCH v4 16/36] mips: Implement the new page table range API
Message-ID: <20230319184536.GA6491@alpha.franken.de>
References: <20230315051444.3229621-1-willy@infradead.org>
 <20230315051444.3229621-17-willy@infradead.org>
 <20230315105022.GA9850@alpha.franken.de>
 <ZBIrkW5EB/uHj4sm@casper.infradead.org>
 <20230317152920.GA11653@alpha.franken.de>
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On Fri, Mar 17, 2023 at 04:29:20PM +0100, Thomas Bogendoerfer wrote:
> On Wed, Mar 15, 2023 at 08:33:21PM +0000, Matthew Wilcox wrote:
> > On Wed, Mar 15, 2023 at 11:50:22AM +0100, Thomas Bogendoerfer wrote:
> > > On Wed, Mar 15, 2023 at 05:14:24AM +0000, Matthew Wilcox (Oracle) wrote:
> > > > Rename _PFN_SHIFT to PFN_PTE_SHIFT.  Convert a few places
> > > > to call set_pte() instead of set_pte_at().  Add set_ptes(),
> > > > update_mmu_cache_range(), flush_icache_pages() and flush_dcache_folio().
> > > 
> > > /local/tbogendoerfer/korg/linux/mm/memory.c: In function ‘set_pte_range’:
> > > /local/tbogendoerfer/korg/linux/mm/memory.c:4290:2: error: implicit declaration of function ‘update_mmu_cache_range’ [-Werror=implicit-function-declaration]
> > >   update_mmu_cache_range(vma, addr, vmf->pte, nr);
> > > 
> > > update_mmu_cache_range() is missing in this patch.
> > 
> > Oops.  And mips was one of the arches I did a test build for!
> > 
> > Looks like we could try to gain some efficiency by passing 'nr' to
> > __update_tlb(), but as far as I can tell, that's only called for r3k and
> > r4k, so maybe it's not worth optimising at this point?
> 
> hmm, not sure if that would help. R4k style TLB has two PTEs mapped
> per TLB entry. So by advancing per page __update_tlb() is called more
> often than needed.

btw. how big is nr going to be ? There are MIPS SoCs out there, which
just have 16 TLBs...

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]