linux-kernel - Re: [PATCH v8 0/5] Add Svade and Svadu Extensions Support

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Message-ID: <mhng-1e3d83bb-a7f4-4fa7-8cfa-2550835026de@palmer-ri-x1c9>
Date: Fri, 20 Sep 2024 01:23:12 -0700 (PDT)
From: Palmer Dabbelt <palmer@...osinc.com>
To: anup@...infault.org
CC: linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org,
  kvm-riscv@...ts.infradead.org, kvm@...r.kernel.org, greentime.hu@...ive.com, vincent.chen@...ive.com,
  yongxuan.wang@...ive.com, Paul Walmsley <paul.walmsley@...ive.com>, aou@...s.berkeley.edu
Subject:     Re: [PATCH v8 0/5] Add Svade and Svadu Extensions Support

On Wed, 21 Aug 2024 07:43:20 PDT (-0700), anup@...infault.org wrote:
> Hi Palmer,
>
> On Fri, Jul 26, 2024 at 2:19 PM Yong-Xuan Wang <yongxuan.wang@...ive.com> wrote:
>>
>> Svade and Svadu extensions represent two schemes for managing the PTE A/D
>> bit. When the PTE A/D bits need to be set, Svade extension intdicates that
>> a related page fault will be raised. In contrast, the Svadu extension
>> supports hardware updating of PTE A/D bits. This series enables Svade and
>> Svadu extensions for both host and guest OS.
>>
>> Regrading the mailing thread[1], we have 4 possible combinations of
>> these extensions in the device tree, the default hardware behavior for
>> these possibilities are:
>> 1) Neither Svade nor Svadu present in DT => It is technically
>>    unknown whether the platform uses Svade or Svadu. Supervisor
>>    software should be prepared to handle either hardware updating
>>    of the PTE A/D bits or page faults when they need updated.
>> 2) Only Svade present in DT => Supervisor must assume Svade to be
>>    always enabled.
>> 3) Only Svadu present in DT => Supervisor must assume Svadu to be
>>    always enabled.
>> 4) Both Svade and Svadu present in DT => Supervisor must assume
>>    Svadu turned-off at boot time. To use Svadu, supervisor must
>>    explicitly enable it using the SBI FWFT extension.
>>
>> The Svade extension is mandatory and the Svadu extension is optional in
>> RVA23 profile. Platforms want to take the advantage of Svadu can choose
>> 3. Those are aware of the profile can choose 4, and Linux won't get the
>> benefit of svadu until the SBI FWFT extension is available.
>>
>> [1] https://lore.kernel.org/linux-kernel/20240527-e9845c06619bca5cd285098c@orel/T/#m29644eb88e241ec282df4ccd5199514e913b06ee
>>
>> ---
>> v8:
>> - fix typo in PATCH1 (Samuel)
>> - use the new extension validating API in PATCH1 (Clément)
>> - update the dtbinding in PATCH2 (Samuel, Conor)
>> - add PATCH4 to fix compile error in get-reg-list test.
>>
>> v7:
>> - fix alignment in PATCH1
>> - update the dtbinding in PATCH2 (Conor, Jessica)
>>
>> v6:
>> - reflect the platform's behavior by riscv_isa_extension_available() and
>>   update the the arch_has_hw_pte_young() in PATCH1 (Conor, Andrew)
>> - update the dtbinding in PATCH2 (Alexandre, Andrew, Anup, Conor)
>> - update the henvcfg condition in PATCH3 (Andrew)
>> - check if Svade is allowed to disabled based on arch_has_hw_pte_young()
>>   in PATCH3
>>
>> v5:
>> - remove all Acked-by and Reviewed-by (Conor, Andrew)
>> - add Svade support
>> - update the arch_has_hw_pte_young() in PATCH1
>> - update the dtbinding in PATCH2 (Alexandre, Andrew)
>> - check the availibility of Svadu for Guest/VM based on
>>   arch_has_hw_pte_young() in PATCH3
>>
>> v4:
>> - fix 32bit kernel build error in PATCH1 (Conor)
>> - update the status of Svadu extension to ratified in PATCH2
>> - add the PATCH4 to suporrt SBI_FWFT_PTE_AD_HW_UPDATING for guest OS
>> - update the PATCH1 and PATCH3 to integrate with FWFT extension
>> - rebase PATCH5 on the lastest get-reg-list test (Andrew)
>>
>> v3:
>> - fix the control bit name to ADUE in PATCH1 and PATCH3
>> - update get-reg-list in PATCH4
>>
>> v2:
>> - add Co-developed-by: in PATCH1
>> - use riscv_has_extension_unlikely() to runtime patch the branch in PATCH1
>> - update dt-binding
>>
>> Yong-Xuan Wang (5):
>>   RISC-V: Add Svade and Svadu Extensions Support
>>   dt-bindings: riscv: Add Svade and Svadu Entries
>>   RISC-V: KVM: Add Svade and Svadu Extensions Support for Guest/VM
>>   KVM: riscv: selftests: Fix compile error
>>   KVM: riscv: selftests: Add Svade and Svadu Extension to get-reg-list
>>     test
>>
>>  .../devicetree/bindings/riscv/extensions.yaml | 28 +++++++++++++++++++
>>  arch/riscv/Kconfig                            |  1 +
>>  arch/riscv/include/asm/csr.h                  |  1 +
>>  arch/riscv/include/asm/hwcap.h                |  2 ++
>>  arch/riscv/include/asm/pgtable.h              | 13 ++++++++-
>>  arch/riscv/include/uapi/asm/kvm.h             |  2 ++
>>  arch/riscv/kernel/cpufeature.c                | 12 ++++++++
>>  arch/riscv/kvm/vcpu.c                         |  4 +++
>>  arch/riscv/kvm/vcpu_onereg.c                  | 15 ++++++++++
>>  .../selftests/kvm/riscv/get-reg-list.c        | 16 ++++++++---
>>  10 files changed, 89 insertions(+), 5 deletions(-)
>>
>> --
>> 2.17.1
>>
>>
>
> Let me know if this series can be taken through the KVM RISC-V tree.
> I can provide you with a shared tag as well.

I think the patchwork bot got confused by patch 4 going to fixes?  It 
says this was merged.

Acked-by: Palmer Dabbelt <palmer@...osinc.com>

if you still want to take it, otherwise just LMK and I'll pick it up.

> Regards,
> Anup