From: Peter Zijlstra <peterz@infradead.org>
To: Dave Hansen <dave.hansen@linux.intel.com>
Cc: will.deacon@arm.com, aneesh.kumar@linux.vnet.ibm.com,
akpm@linux-foundation.org, npiggin@gmail.com,
linux-arch@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, linux@armlinux.org.uk,
heiko.carstens@de.ibm.com
Subject: Re: [RFC][PATCH 03/11] x86/mm: Page size aware flush_tlb_mm_range()
Date: Thu, 13 Sep 2018 20:42:30 +0200 [thread overview]
Message-ID: <20180913184230.GD24124@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <f89e61a3-0eb0-3d00-fbaa-f30c2cf60be3@linux.intel.com>
On Thu, Sep 13, 2018 at 10:22:58AM -0700, Dave Hansen wrote:
> > +static inline void tlb_flush(struct mmu_gather *tlb)
> > +{
> > + unsigned long start = 0UL, end = TLB_FLUSH_ALL;
> > + unsigned int invl_shift = tlb_get_unmap_shift(tlb);
>
> I had to go back and look at
>
> https://patchwork.kernel.org/patch/10587207/
I so hate patchwork...
> to figure out what was going on. I wonder if we could make the code a
> bit more standalone.
>
> This at least needs a comment about what it's getting from 'tlb'. Maybe
> just:
>
> /* Find the smallest page size that we unmapped: */
>
> > --- a/arch/x86/include/asm/tlbflush.h
> > +++ b/arch/x86/include/asm/tlbflush.h
> > @@ -507,23 +507,25 @@ struct flush_tlb_info {
> > unsigned long start;
> > unsigned long end;
> > u64 new_tlb_gen;
> > + unsigned int invl_shift;
> > };
>
> Maybe we really should just call this flush_stride or something.
But its a shift, not a size. stride_shift?
> > #define local_flush_tlb() __flush_tlb()
> >
> > #define flush_tlb_mm(mm) flush_tlb_mm_range(mm, 0UL, TLB_FLUSH_ALL, 0UL)
> >
> > -#define flush_tlb_range(vma, start, end) \
> > - flush_tlb_mm_range(vma->vm_mm, start, end, vma->vm_flags)
> > +#define flush_tlb_range(vma, start, end) \
> > + flush_tlb_mm_range((vma)->vm_mm, start, end, \
> > + (vma)->vm_flags & VM_HUGETLB ? PMD_SHIFT : PAGE_SHIFT)
>
> This is safe. But, Couldn't this PMD_SHIFT also be PUD_SHIFT for a 1G
> hugetlb page?
It could be, but can we tell at that point?
> > void native_flush_tlb_others(const struct cpumask *cpumask,
> > --- a/arch/x86/mm/tlb.c
> > +++ b/arch/x86/mm/tlb.c
> > @@ -522,12 +522,12 @@ static void flush_tlb_func_common(const
> > f->new_tlb_gen == mm_tlb_gen) {
> > /* Partial flush */
> > unsigned long addr;
> > - unsigned long nr_pages = (f->end - f->start) >> PAGE_SHIFT;
> > + unsigned long nr_pages = (f->end - f->start) >> f->invl_shift;
>
> We might want to make this nr_invalidations or nr_flushes now so we
> don't get it confused with PAGE_SIZE stuff.
Sure, can rename.
> Otherwise, this makes me a *tiny* bit nervous. I think we're good about
> ensuring that we fully flush 4k mappings from the TLB before going up to
> a 2MB mapping because of all the errata we've had there over the years.
> But, had we left 4k mappings around, the old flushing code would have
> cleaned them up for us.
Indeed.
> This certainly tightly ties the invalidations to what was in the page
> tables. If that diverged from the TLB at some point, there's certainly
> more exposure here.
>
> Looks fun, though. :)
:-)
next prev parent reply other threads:[~2018-09-13 18:42 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-13 9:21 [RFC][PATCH 00/11] my generic mmu_gather patches Peter Zijlstra
2018-09-13 9:21 ` [RFC][PATCH 01/11] asm-generic/tlb: Provide a comment Peter Zijlstra
2018-09-13 10:30 ` Martin Schwidefsky
2018-09-13 10:57 ` Peter Zijlstra
2018-09-13 12:18 ` Martin Schwidefsky
2018-09-13 12:39 ` Peter Zijlstra
2018-09-14 10:28 ` Martin Schwidefsky
2018-09-14 13:02 ` Peter Zijlstra
2018-09-14 14:07 ` Martin Schwidefsky
2018-09-14 16:48 ` Will Deacon
2018-09-19 11:33 ` Peter Zijlstra
2018-09-19 11:51 ` Peter Zijlstra
2018-09-19 12:23 ` Will Deacon
2018-09-19 13:12 ` Peter Zijlstra
2018-09-13 9:21 ` [RFC][PATCH 02/11] asm-generic/tlb: Provide HAVE_MMU_GATHER_PAGE_SIZE Peter Zijlstra
2018-09-14 16:56 ` Will Deacon
2018-09-13 9:21 ` [RFC][PATCH 03/11] x86/mm: Page size aware flush_tlb_mm_range() Peter Zijlstra
2018-09-13 17:22 ` Dave Hansen
2018-09-13 18:42 ` Peter Zijlstra [this message]
2018-09-13 18:46 ` Peter Zijlstra
2018-09-13 18:48 ` Peter Zijlstra
2018-09-13 18:49 ` Dave Hansen
2018-09-13 18:47 ` Dave Hansen
2018-09-13 9:21 ` [RFC][PATCH 04/11] asm-generic/tlb: Provide generic VIPT cache flush Peter Zijlstra
2018-09-14 16:56 ` Will Deacon
2018-09-13 9:21 ` [RFC][PATCH 05/11] asm-generic/tlb: Provide generic tlb_flush Peter Zijlstra
2018-09-13 13:09 ` Jann Horn
2018-09-13 14:06 ` Peter Zijlstra
2018-09-13 9:21 ` [RFC][PATCH 06/11] asm-generic/tlb: Conditionally provide tlb_migrate_finish() Peter Zijlstra
2018-09-14 16:57 ` Will Deacon
2018-09-13 9:21 ` [RFC][PATCH 07/11] arm/tlb: Convert to generic mmu_gather Peter Zijlstra
2018-09-18 14:10 ` Will Deacon
2018-09-19 11:28 ` Peter Zijlstra
2018-09-19 12:24 ` Will Deacon
2018-09-19 11:30 ` Peter Zijlstra
2018-09-13 9:21 ` [RFC][PATCH 08/11] ia64/tlb: Conver " Peter Zijlstra
2018-09-13 9:21 ` [RFC][PATCH 09/11] sh/tlb: Convert SH " Peter Zijlstra
2018-09-13 9:21 ` [RFC][PATCH 10/11] um/tlb: Convert " Peter Zijlstra
2018-09-13 9:21 ` [RFC][PATCH 11/11] arch/tlb: Clean up simple architectures Peter Zijlstra
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