[PATCH v8 0/5] Add Svade and Svadu Extensions Support

Yong-Xuan Wang
2024-07-26T08:49:36Z

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(-)

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2.17.1