linux-kernel - Re: [RFC][PATCH 03/11] x86/mm: Page size aware flush_tlb_mm

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Message-ID: <93b19cab-779b-b5dd-a53b-df2c86241d4f@linux.intel.com>
Date:   Thu, 13 Sep 2018 11:49:28 -0700
From:   Dave Hansen <dave.hansen@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     will.deacon@....com, aneesh.kumar@...ux.vnet.ibm.com,
        akpm@...ux-foundation.org, npiggin@...il.com,
        linux-arch@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux@...linux.org.uk,
        heiko.carstens@...ibm.com
Subject: Re: [RFC][PATCH 03/11] x86/mm: Page size aware flush_tlb_mm_range()

On 09/13/2018 11:46 AM, Peter Zijlstra wrote:
> On Thu, Sep 13, 2018 at 08:42:30PM +0200, Peter Zijlstra wrote:
>>>> +#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?
> I had me a look in higetlb.h, would something like so work?
> 
> #define flush_tlb_range(vma, start, end)			\
> 	flush_tlb_mm_range((vma)->vm_mm, start, end,		\
> 			   huge_page_shift(hstate_vma(vma)))
> 

I think you still need the VM_HUGETLB check somewhere because
hstate_vma() won't work on non-VM_HUGETLB VMAs.  But, yeah, something
close to that should be OK.