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

Anup Patel
2024-07-19T16:09:25Z

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_v1 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.

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

arch/riscv/include/asm/kvm_nacl.h | 237 ++++++++++++++++++++++++++++++
arch/riscv/include/asm/sbi.h | 120 +++++++++++++++
arch/riscv/kvm/Makefile | 27 ++--
arch/riscv/kvm/aia.c | 114 +++++++++-----
arch/riscv/kvm/main.c | 53 ++++++-
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, 935 insertions(+), 178 deletions(-)
create mode 100644 arch/riscv/include/asm/kvm_nacl.h
create mode 100644 arch/riscv/kvm/nacl.c

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2.34.1