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[24.6.216.183]) by smtp.gmail.com with ESMTPSA id e6sm5125083pgf.59.2021.10.04.12.24.15 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Mon, 04 Oct 2021 12:24:16 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 14.0 \(3654.120.0.1.13\)) Subject: Re: [PATCH 1/2] mm/mprotect: use mmu_gather From: Nadav Amit In-Reply-To: <20211003121019.GF4323@worktop.programming.kicks-ass.net> Date: Mon, 4 Oct 2021 12:24:14 -0700 Cc: Andrew Morton , LKML , Linux-MM , Peter Xu , Andrea Arcangeli , Andrew Cooper , Andy Lutomirski , Dave Hansen , Thomas Gleixner , Will Deacon , Yu Zhao , Nick Piggin , x86@kernel.org Content-Transfer-Encoding: quoted-printable Message-Id: <620B1A38-1457-4F77-8666-E73A318392B6@gmail.com> References: <20210925205423.168858-1-namit@vmware.com> <20210925205423.168858-2-namit@vmware.com> <20211003121019.GF4323@worktop.programming.kicks-ass.net> To: Peter Zijlstra X-Mailer: Apple Mail (2.3654.120.0.1.13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Oct 3, 2021, at 5:10 AM, Peter Zijlstra = wrote: >=20 > On Sat, Sep 25, 2021 at 01:54:22PM -0700, Nadav Amit wrote: >=20 >> @@ -338,25 +344,25 @@ static unsigned long = change_protection_range(struct vm_area_struct *vma, >> struct mm_struct *mm =3D vma->vm_mm; >> pgd_t *pgd; >> unsigned long next; >> - unsigned long start =3D addr; >> unsigned long pages =3D 0; >> + struct mmu_gather tlb; >>=20 >> BUG_ON(addr >=3D end); >> pgd =3D pgd_offset(mm, addr); >> flush_cache_range(vma, addr, end); >> inc_tlb_flush_pending(mm); >=20 > That seems unbalanced... Bad rebase. Thanks for catching it! >=20 >> + tlb_gather_mmu(&tlb, mm); >> + tlb_start_vma(&tlb, vma); >> do { >> next =3D pgd_addr_end(addr, end); >> if (pgd_none_or_clear_bad(pgd)) >> continue; >> - pages +=3D change_p4d_range(vma, pgd, addr, next, = newprot, >> + pages +=3D change_p4d_range(&tlb, vma, pgd, addr, next, = newprot, >> cp_flags); >> } while (pgd++, addr =3D next, addr !=3D end); >>=20 >> - /* Only flush the TLB if we actually modified any entries: */ >> - if (pages) >> - flush_tlb_range(vma, start, end); >> - dec_tlb_flush_pending(mm); >=20 > ... 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=E2=80=99ll keep it.=