From: Catalin Marinas <catalin.marinas@arm.com>
To: Dave Hansen <dave.hansen@intel.com>
Cc: Jisheng Zhang <jszhang@kernel.org>, Will Deacon <will@kernel.org>,
"Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Nick Piggin <npiggin@gmail.com>,
Peter Zijlstra <peterz@infradead.org>,
Paul Walmsley <paul.walmsley@sifive.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>, Arnd Bergmann <arnd@arndb.de>,
linux-arch@vger.kernel.org, linux-mm@kvack.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org,
Nadav Amit <namit@vmware.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Andy Lutomirski <luto@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>, Yu Zhao <yuzhao@google.com>,
x86@kernel.org
Subject: Re: [PATCH 1/2] mm/tlb: fix fullmm semantics
Date: Wed, 3 Jan 2024 21:54:32 +0000 [thread overview]
Message-ID: <ZZXXmFthrXO6G9OE@arm.com> (raw)
In-Reply-To: <6ee6340a-ffe2-4106-b845-47cf443558c3@intel.com>
On Wed, Jan 03, 2024 at 12:26:29PM -0800, Dave Hansen wrote:
> On 1/3/24 10:05, Catalin Marinas wrote:
> >> --- a/mm/mmu_gather.c
> >> +++ b/mm/mmu_gather.c
> >> @@ -384,7 +384,7 @@ void tlb_finish_mmu(struct mmu_gather *tlb)
> >> * On x86 non-fullmm doesn't yield significant difference
> >> * against fullmm.
> >> */
> >> - tlb->fullmm = 1;
> >> + tlb->need_flush_all = 1;
> >> __tlb_reset_range(tlb);
> >> tlb->freed_tables = 1;
> >> }
> > The optimisation here was added about a year later in commit
> > 7a30df49f63a ("mm: mmu_gather: remove __tlb_reset_range() for force
> > flush"). Do we still need to keep freed_tables = 1 here? I'd say only
> > __tlb_reset_range().
>
> I think the __tlb_reset_range() can be dangerous if it clears
> ->freed_tables. On x86 at least, it might lead to skipping the TLB IPI
> for CPUs that are in lazy TLB mode. When those wake back up they might
> start using the freed page tables.
You are right, I did not realise freed_tables is reset in
__tlb_reset_range().
--
Catalin
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next prev parent reply other threads:[~2024-01-03 21:55 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-28 8:46 [PATCH 0/2] riscv: tlb: avoid tlb flushing on exit & execve Jisheng Zhang
2023-12-28 8:46 ` [PATCH 1/2] mm/tlb: fix fullmm semantics Jisheng Zhang
2023-12-30 9:54 ` Nadav Amit
2024-01-02 2:41 ` Jisheng Zhang
2024-01-04 13:26 ` Nadav Amit
2024-01-04 14:40 ` Will Deacon
2024-01-03 17:50 ` Will Deacon
2024-01-03 17:57 ` Will Deacon
2024-01-03 18:05 ` Catalin Marinas
2024-01-03 20:26 ` Dave Hansen
2024-01-03 21:54 ` Catalin Marinas [this message]
2023-12-28 8:46 ` [PATCH 2/2] riscv: tlb: avoid tlb flushing if fullmm == 1 Jisheng Zhang
2023-12-30 18:26 ` Alexandre Ghiti
2024-01-02 3:12 ` Jisheng Zhang
2024-01-04 13:00 ` Alexandre Ghiti
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