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[24.6.216.183]) by smtp.gmail.com with ESMTPSA id y6sm3667118pfn.123.2021.02.03.19.20.27 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Wed, 03 Feb 2021 19:20:28 -0800 (PST) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 13.4 \(3608.120.23.2.4\)) Subject: Re: [RFC 01/20] mm/tlb: fix fullmm semantics From: Nadav Amit In-Reply-To: <20210203094459.GA18493@willie-the-truck> Date: Wed, 3 Feb 2021 19:20:26 -0800 Cc: Peter Zijlstra , Andrea Arcangeli , Andrew Morton , Andy Lutomirski , Dave Hansen , Thomas Gleixner , Yu Zhao , Nick Piggin , X86 ML , Linux-MM , LKML Content-Transfer-Encoding: quoted-printable Message-Id: <3EA63C0E-3420-4194-AA4F-A05A0B0AFF95@gmail.com> References: <20210131001132.3368247-1-namit@vmware.com> <20210131001132.3368247-2-namit@vmware.com> <52673507-2C30-4AC6-8EBC-B5A313827FB0@gmail.com> <5E9B0429-7E72-4E86-B91B-4718C4134B0F@gmail.com> <20210203094459.GA18493@willie-the-truck> To: Will Deacon X-Mailer: Apple Mail (2.3608.120.23.2.4) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: > On Feb 3, 2021, at 1:44 AM, Will Deacon wrote: >=20 > On Tue, Feb 02, 2021 at 01:35:38PM -0800, Nadav Amit wrote: >>> On Feb 2, 2021, at 3:00 AM, Peter Zijlstra = wrote: >>>=20 >>> On Tue, Feb 02, 2021 at 01:32:36AM -0800, Nadav Amit wrote: >>>>> On Feb 1, 2021, at 3:36 AM, Peter Zijlstra = wrote: >>>>>=20 >>>>>=20 >>>>> https://lkml.kernel.org/r/20210127235347.1402-1-will@kernel.org >>>>=20 >>>> I have seen this series, and applied my patches on it. >>>>=20 >>>> Despite Will=E2=80=99s patches, there were still inconsistencies = between fullmm >>>> and need_flush_all. >>>>=20 >>>> Am I missing something? >>>=20 >>> I wasn't aware you were on top. I'll look again. >>=20 >> Looking on arm64=E2=80=99s tlb_flush() makes me think that there is = currently a bug >> that this patch fixes. Arm64=E2=80=99s tlb_flush() does: >>=20 >> /* >> * If we're tearing down the address space then we only care = about >> * invalidating the walk-cache, since the ASID allocator won't >> * reallocate our ASID without invalidating the entire TLB. >> */ >> if (tlb->fullmm) { >> if (!last_level) >> flush_tlb_mm(tlb->mm); >> return; >> }=20 >>=20 >> But currently tlb_mmu_finish() can mistakenly set fullmm incorrectly = (if >> mm_tlb_flush_nested() is true), which might skip the TLB flush. >=20 > But in that case isn't 'freed_tables' set to 1, so 'last_level' will = be > false and we'll do the flush in the code above? Indeed. You are right. So no rush.=