From: Nadav Amit <nadav.amit@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>, Peter Xu <peterx@redhat.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Andy Lutomirski <luto@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Will Deacon <will@kernel.org>, Yu Zhao <yuzhao@google.com>,
Nick Piggin <npiggin@gmail.com>,
x86@kernel.org
Subject: Re: [PATCH 1/2] mm/mprotect: use mmu_gather
Date: Mon, 4 Oct 2021 12:24:14 -0700 [thread overview]
Message-ID: <620B1A38-1457-4F77-8666-E73A318392B6@gmail.com> (raw)
In-Reply-To: <20211003121019.GF4323@worktop.programming.kicks-ass.net>
> On Oct 3, 2021, at 5:10 AM, Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Sat, Sep 25, 2021 at 01:54:22PM -0700, Nadav Amit wrote:
>
>> @@ -338,25 +344,25 @@ static unsigned long change_protection_range(struct vm_area_struct *vma,
>> struct mm_struct *mm = vma->vm_mm;
>> pgd_t *pgd;
>> unsigned long next;
>> - unsigned long start = addr;
>> unsigned long pages = 0;
>> + struct mmu_gather tlb;
>>
>> BUG_ON(addr >= end);
>> pgd = pgd_offset(mm, addr);
>> flush_cache_range(vma, addr, end);
>> inc_tlb_flush_pending(mm);
>
> That seems unbalanced...
Bad rebase. Thanks for catching it!
>
>> + tlb_gather_mmu(&tlb, mm);
>> + tlb_start_vma(&tlb, vma);
>> do {
>> next = pgd_addr_end(addr, end);
>> if (pgd_none_or_clear_bad(pgd))
>> continue;
>> - pages += change_p4d_range(vma, pgd, addr, next, newprot,
>> + pages += change_p4d_range(&tlb, vma, pgd, addr, next, newprot,
>> cp_flags);
>> } while (pgd++, addr = next, addr != end);
>>
>> - /* Only flush the TLB if we actually modified any entries: */
>> - if (pages)
>> - flush_tlb_range(vma, start, end);
>> - dec_tlb_flush_pending(mm);
>
> ... seeing you do remove the extra decrement.
Is it really needed? We do not put this comment elsewhere for
tlb_finish_mmu(). But no problem, I’ll keep it.
next prev parent reply other threads:[~2021-10-04 19:24 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-25 20:54 [PATCH 0/2] mm/mprotect: avoid unnecessary TLB flushes Nadav Amit
2021-09-25 20:54 ` [PATCH 1/2] mm/mprotect: use mmu_gather Nadav Amit
2021-10-03 12:10 ` Peter Zijlstra
2021-10-04 19:24 ` Nadav Amit [this message]
2021-10-05 6:53 ` Peter Zijlstra
2021-10-05 16:34 ` Nadav Amit
2021-10-11 3:45 ` Nadav Amit
2021-10-12 10:16 ` Peter Xu
2021-10-12 17:31 ` Nadav Amit
2021-10-12 23:20 ` Peter Xu
2021-10-13 15:59 ` Nadav Amit
2021-09-25 20:54 ` [PATCH 2/2] mm/mprotect: do not flush on permission promotion Nadav Amit
2021-10-07 12:13 ` David Hildenbrand
2021-10-07 16:16 ` Nadav Amit
2021-10-07 17:07 ` David Hildenbrand
2021-10-08 6:06 ` Nadav Amit
2021-10-08 7:35 ` David Hildenbrand
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