[PATCH v2 00/13] Accelerate KVM RISC-V when running as a guest

[Anup Patel]

On Mon, Oct 21, 2024 at 1:17 AM Anup Patel <apatel at ventanamicro.com> wrote:
>
> The KVM RISC-V hypervisor might be running as a guest under some other
> host hypervisor in which case the complete H-extension functionality will
> be trap-n-emulated by the host hypervisor. In this case, the KVM RISC-V
> performance can be accelerated using the SBI nested acceleration (NACL)
> extension if the host hypervisor provides it.
>
> These series extends KVM RISC-V to use SBI NACL extension whenever
> underlying SBI implementation (aka host hypervisor) provides it.
>
> These patches can also be found in the riscv_sbi_nested_v2 branch at:
> https://github.com/avpatel/linux.git
>
> To test these patches, run KVM RISC-V as Guest under latest Xvisor
> found at: https://github.com/xvisor/xvisor.git
>
> For the steps to test on Xvisor, refer the Xvisor documentation
> <xvisor_source>/docs/riscv/riscv64-qemu.txt with two small changes:
>
> 1) In step#11, make sure compressed kvm.ko, guest kernel image, and
>    kvmtool are present in the rootfs.img
> 2) In step#14, make sure AIA is available to Xvisor by using
>    "virt,aia=aplic-imsic" as the QEMU machine name.
>
> Changes since v1:
>  - Dropped nacl_shmem_fast() macro from PATCH8
>  - Added comments in PATCH8 about which back-to-back ncsr_xyz()
>    macros are sub-optimal
>  - Moved nacl_scratch_xyz() macros to PATCH8
>
> Anup Patel (13):
>   RISC-V: KVM: Order the object files alphabetically
>   RISC-V: KVM: Save/restore HSTATUS in C source
>   RISC-V: KVM: Save/restore SCOUNTEREN in C source
>   RISC-V: KVM: Break down the __kvm_riscv_switch_to() into macros
>   RISC-V: KVM: Replace aia_set_hvictl() with aia_hvictl_value()
>   RISC-V: KVM: Don't setup SGEI for zero guest external interrupts
>   RISC-V: Add defines for the SBI nested acceleration extension
>   RISC-V: KVM: Add common nested acceleration support
>   RISC-V: KVM: Use nacl_csr_xyz() for accessing H-extension CSRs
>   RISC-V: KVM: Use nacl_csr_xyz() for accessing AIA CSRs
>   RISC-V: KVM: Use SBI sync SRET call when available
>   RISC-V: KVM: Save trap CSRs in kvm_riscv_vcpu_enter_exit()
>   RISC-V: KVM: Use NACL HFENCEs for KVM request based HFENCEs

Queued this series for Linux-6.13

Regards,
Anup

>
>  arch/riscv/include/asm/kvm_nacl.h | 245 ++++++++++++++++++++++++++++++
>  arch/riscv/include/asm/sbi.h      | 120 +++++++++++++++
>  arch/riscv/kvm/Makefile           |  27 ++--
>  arch/riscv/kvm/aia.c              | 114 +++++++++-----
>  arch/riscv/kvm/main.c             |  51 ++++++-
>  arch/riscv/kvm/mmu.c              |   4 +-
>  arch/riscv/kvm/nacl.c             | 152 ++++++++++++++++++
>  arch/riscv/kvm/tlb.c              |  57 ++++---
>  arch/riscv/kvm/vcpu.c             | 184 ++++++++++++++++------
>  arch/riscv/kvm/vcpu_switch.S      | 137 +++++++++++------
>  arch/riscv/kvm/vcpu_timer.c       |  28 ++--
>  11 files changed, 941 insertions(+), 178 deletions(-)
>  create mode 100644 arch/riscv/include/asm/kvm_nacl.h
>  create mode 100644 arch/riscv/kvm/nacl.c
>
> --
> 2.43.0
>