From: Guo Ren <guoren@kernel.org>
To: Jean-Philippe Brucker <jean-philippe@linaro.org>
Cc: aou@eecs.berkeley.edu,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Arnd Bergmann <arnd@arndb.de>,
Marc Zyngier <marc.zyngier@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Palmer Dabbelt <palmer@sifive.com>,
iommu@lists.linux-foundation.org,
Mike Rapoport <rppt@linux.ibm.com>,
Anup Patel <anup.Patel@wdc.com>,
Atish Patra <Atish.Patra@wdc.com>,
Julien Grall <julien.grall@arm.com>,
gary@garyguo.net, Paul Walmsley <paul.walmsley@sifive.com>,
linux-riscv@lists.infradead.org, Will Deacon <will@kernel.org>,
kvmarm@lists.cs.columbia.edu,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH RFC 11/14] arm64: Move the ASID allocator code in a separate file
Date: Thu, 19 Sep 2019 21:07:15 +0800 [thread overview]
Message-ID: <CAJF2gTRbyfrUqAULPqJTXdxx8YOscPqAEuMsoJ+dTNobNrUV1g@mail.gmail.com> (raw)
In-Reply-To: <057a0af3-93f7-271c-170e-4b31e6894c3c@linaro.org>
Hi,
On Mon, Sep 16, 2019 at 8:57 PM Jean-Philippe Brucker
<jean-philippe@linaro.org> wrote:
> On 13/09/2019 09:13, Guo Ren wrote:
> > Another idea is seperate remote TLB invalidate into two instructions:
> >
> > - sfence.vma.b.asyc
> > - sfence.vma.b.barrier // wait all async TLB invalidate operations
> > finished for all harts.
>
> It's not clear to me how this helps, but I probably don't have the whole
> picture. If you have a place where it is safe to wait for the barrier to
> complete, why not do the whole invalidate there?
>
> > (I remember who mentioned me separate them into two instructions after
> > session. Anup? Is the idea right ?)
Forget it, I still use irq signal in my formal proposal [1]. I also
couldn't image the whole picture :P
> > To solve the problem, we could define a async mode in sfence.vma.b to
> > slove the problem and finished with per_cpu_irq/exception.
>
> The solution I had to this problem is pinning the ASID [1] used by the
> IOMMU, to prevent the CPU from recycling the ASID on rollover. This way
> the CPU doesn't have to wait for IOMMU invalidations to complete, when
> scheduling a task that might not even have anything to do with the IOMMU.
>
> In the Arm SMMU, ASID and IOASID (PASID) are separate identifiers. IOASID
> indexes an entry in the context descriptor table, which contains the ASID.
> So with unpinned shared ASID you don't need to invalidate the ATC on
> rollover, since the IOASID doesn't change, but you do need to modify the
> context descriptor and invalidate cached versions of it.
The terminology confused me a lot. I perfer use PASID for IOMMU and
ASID is for CPU.
Arm's entry of the context descriptor table contains a "IOASID"
IOASID != ASID for CPU_TLB and IOMMU_TLB.
When you say "since the IOASID doesn't change",Is it PASID or my IOASID ? -_*!
PASID in PCI-sig was used to determine transfer address space.
For intel, the entry which is indexed by PASID also contain S1/S2.PGD
and DID(VMID).
For arm, the entry which is indexed by PASID only contain S1.PGD and
IOASID. Compare to Intel Vt-d Scalable mode, arm's design can't
support PCI Virtual Function.
>
> Once you have pinned ASIDs, you could also declare that IOASID = ASID. I
> don't remember finding an argument to strictly forbid it, even though ASID
> and IOASID have different sizes on Arm (respectively 8/16 and 20 bits).
ASID and IOASID are hard to keep the same between CPU system and IOMMU
system. So I introduce S1/S2.PGD.PPN as a bridge between CPUs and
IOMMUs.
See my proposal [1]
1: https://lore.kernel.org/linux-csky/1568896556-28769-1-git-send-email-guoren@kernel.org/T/#u
--
Best Regards
Guo Ren
ML: https://lore.kernel.org/linux-csky/
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next prev parent reply other threads:[~2019-09-19 13:07 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-21 16:36 [PATCH RFC 00/14] kvm/arm: Align the VMID allocation with the arm64 ASID one Julien Grall
2019-03-21 16:36 ` [PATCH RFC 01/14] arm64/mm: Introduce asid_info structure and move asid_generation/asid_map to it Julien Grall
2019-03-21 17:03 ` Suzuki K Poulose
2019-03-21 17:27 ` Julien Grall
2019-03-21 16:36 ` [PATCH RFC 02/14] arm64/mm: Move active_asids and reserved_asids to asid_info Julien Grall
2019-03-21 16:36 ` [PATCH RFC 03/14] arm64/mm: Move bits " Julien Grall
2019-03-21 16:36 ` [PATCH RFC 04/14] arm64/mm: Move the variable lock and tlb_flush_pending " Julien Grall
2019-03-21 16:36 ` [PATCH RFC 05/14] arm64/mm: Remove dependency on MM in new_context Julien Grall
2019-03-21 16:36 ` [PATCH RFC 06/14] arm64/mm: Store the number of asid allocated per context Julien Grall
2019-03-21 16:36 ` [PATCH RFC 07/14] arm64/mm: Introduce NUM_ASIDS Julien Grall
2019-03-21 16:36 ` [PATCH RFC 08/14] arm64/mm: Split asid_inits in 2 parts Julien Grall
2019-03-21 16:36 ` [PATCH RFC 09/14] arm64/mm: Split the function check_and_switch_context in 3 parts Julien Grall
2019-03-21 16:36 ` [PATCH RFC 10/14] arm64/mm: Introduce a callback to flush the local context Julien Grall
2019-03-21 16:36 ` [PATCH RFC 11/14] arm64: Move the ASID allocator code in a separate file Julien Grall
2019-06-05 16:56 ` Julien Grall
2019-06-05 20:41 ` Palmer Dabbelt
2019-06-11 1:56 ` Gary Guo
2019-06-19 8:07 ` Guo Ren
2019-06-19 8:54 ` Julien Grall
2019-06-19 9:12 ` Will Deacon
2019-06-19 12:18 ` Guo Ren
2019-06-19 12:39 ` Will Deacon
2019-06-20 9:33 ` Guo Ren
2019-06-24 10:40 ` Will Deacon
2019-06-25 7:25 ` Palmer Dabbelt
2019-09-07 23:52 ` Guo Ren
2019-09-12 14:02 ` Will Deacon
2019-09-12 14:59 ` Guo Ren
2019-09-13 7:13 ` Guo Ren
2019-09-14 8:49 ` Guo Ren
2019-09-16 12:57 ` Jean-Philippe Brucker
2019-09-19 13:07 ` Guo Ren [this message]
2019-09-19 15:18 ` Jean-Philippe Brucker
2019-09-20 0:07 ` Guo Ren
2019-09-20 7:18 ` Jean-Philippe Brucker
2019-09-14 14:01 ` Palmer Dabbelt
2019-09-15 5:03 ` Anup Patel
2019-09-16 18:18 ` Will Deacon
2019-09-16 18:28 ` Palmer Dabbelt
2019-09-17 3:42 ` Anup Patel
2019-09-19 13:36 ` Guo Ren
2019-06-19 11:51 ` Guo Ren
2019-06-19 12:52 ` Julien Grall
2019-06-21 14:16 ` Catalin Marinas
2019-06-23 16:35 ` Guo Ren
2019-06-24 10:22 ` Will Deacon
2019-06-27 9:41 ` qi.fuli
2019-06-27 10:26 ` Will Deacon
2019-06-24 15:38 ` Catalin Marinas
2019-06-30 4:29 ` Guo Ren
2019-07-01 9:17 ` Catalin Marinas
2019-07-16 3:31 ` Guo Ren
2019-07-22 16:38 ` Catalin Marinas
2019-03-21 16:36 ` [PATCH RFC 12/14] arm64/lib: asid: Allow user to update the context under the lock Julien Grall
2019-03-21 16:36 ` [PATCH RFC 13/14] arm/kvm: Introduce a new VMID allocator Julien Grall
2019-03-21 16:36 ` [PATCH RFC 14/14] kvm/arm: Align the VMID allocation with the arm64 ASID one Julien Grall
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