From: Christoph Hellwig <hch@infradead.org>
To: Alistair Popple <apopple@nvidia.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
robin.murphy@arm.com, will@kernel.org, nicolinc@nvidia.com,
linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org,
kvmarm@lists.cs.columbia.edu, jgg@nvidia.com,
John Hubbard <jhubbard@nvidia.com>
Subject: Re: [PATCH] mmu_notifiers: Notify on pte permission upgrades
Date: Mon, 22 May 2023 23:45:12 -0700 [thread overview]
Message-ID: <ZGxg+I8FWz3YqBMk@infradead.org> (raw)
In-Reply-To: <20230522063725.284686-1-apopple@nvidia.com>
On Mon, May 22, 2023 at 04:37:25PM +1000, Alistair Popple wrote:
> This problem was discovered during testing of an ARM SMMU
> implementation that does not support broadcast TLB maintenance
> (BTM). In this case the SMMU driver uses notifiers to issue TLB
> invalidates. For read-only to read-write pte upgrades the SMMU
> continually returned a read-only PTE to the device, even though the
> CPU had a read-write PTE installed.
>
> Sending a mmu notifier event to the SMMU driver fixes the problem by
> flushing secondary TLB entries. A new notifier event type is added so
> drivers may filter out these invalidations if not required. Note a
> driver should never upgrade or install a PTE in response to this mmu
> notifier event as it is not synchronised against other PTE operations.
I don't see these SMMU driver changes anywhere. I.e. you're adding dead
code as far as I can tell.
prev parent reply other threads:[~2023-05-23 6:45 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-22 6:37 Alistair Popple
2023-05-22 7:15 ` Qi Zheng
2023-05-22 7:45 ` Alistair Popple
2023-05-22 8:28 ` Qi Zheng
2023-05-22 15:09 ` Catalin Marinas
2023-05-22 23:52 ` Alistair Popple
2023-05-22 18:34 ` Sean Christopherson
2023-05-22 23:50 ` Alistair Popple
2023-05-23 0:06 ` Sean Christopherson
2023-05-23 0:43 ` Alistair Popple
2023-05-23 1:13 ` John Hubbard
2023-05-23 4:35 ` Alistair Popple
2023-05-23 0:55 ` John Hubbard
2023-05-23 1:12 ` Alistair Popple
2023-05-23 6:45 ` Christoph Hellwig [this message]
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