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

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Message-ID: <CAAhSdy05BXUZu6BNUoDWoEVd_YiM0Dpqg=t5WYUX7+cacnO2Hg@mail.gmail.com>
Date: Wed, 21 Aug 2024 20:13:20 +0530
From: Anup Patel <anup@...infault.org>
To: Palmer Dabbelt <palmer@...belt.com>, Palmer Dabbelt <palmer@...osinc.com>
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, Yong-Xuan Wang <yongxuan.wang@...ive.com>, 
	Paul Walmsley <paul.walmsley@...ive.com>, Albert Ou <aou@...s.berkeley.edu>
Subject: Re: [PATCH v8 0/5] Add Svade and Svadu Extensions Support

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.

Regards,
Anup