[RFC PATCH 00/14] RISC-V: Add steal-time support

Andrew Jones
2023-04-17T10:34:27Z

One frequently touted benefit of virtualization is the ability to
consolidate machines, increasing resource utilization. It may even be
desirable to overcommit, at the risk of one or more VCPUs having to wait.
Hypervisors which have interfaces for guests to retrieve the amount of
time each VCPU had to wait give observers within the guests ways to
account for less progress than would otherwise be expected. The SBI STA
extension proposal[1] provides a standard interface for guest VCPUs to
retrieve the amount of time "stolen".

This series has three parts:
1) Patches 01-04 - Add paravirt support to RISC-V and implement
steal-time accounting support using the SBI STA
extension.
2) Patches 05-10 - Implement SBI STA in KVM so KVM guests, such as
Linux guests which enable the paravirt steal-time
support, can be enlightened about stolen time.
3) Patches 11-12 - Add support to the KVM selftests steal_time test
for RISC-V.

Note, while we can review and revise this series now, we'll keep the
RFC tag and refrain from merging it until the proposed SBI extension
has been ratified.

[1] https://lists.riscv.org/g/tech-prs/message/401

This patches are also available here
https://github.com/jones-drew/linux/commits/kvm/steal-time-rfc-v1

Thanks,
drew

Andrew Jones (14):
RISC-V: paravirt: Add skeleton for pv-time support
RISC-V: Add SBI STA extension definitions
RISC-V: paravirt: Implement steal-time support
RISC-V: paravirt: Add kconfigs
RISC-V: KVM: Add SBI STA extension skeleton
RISC-V: KVM: Add steal-update vcpu request
RISC-V: KVM: Add SBI STA info to vcpu_arch
RISC-V: KVM: Implement SBI STA extension
RISC-V: KVM: Add support for SBI extension registers
RISC-V: KVM: Add support for SBI STA registers
KVM: selftests: riscv: Move sbi_ecall to processor.c
KVM: selftests: riscv: Add guest_sbi_probe_extension
KVM: selftests: riscv: Add RISCV_SBI_EXT_REG
KVM: selftests: riscv: Add steal_time test support

.../admin-guide/kernel-parameters.txt | 6 +-
arch/riscv/Kconfig | 19 ++
arch/riscv/include/asm/kvm_host.h | 9 +
arch/riscv/include/asm/kvm_vcpu_sbi.h | 5 +
arch/riscv/include/asm/paravirt.h | 29 +++
arch/riscv/include/asm/paravirt_api_clock.h | 1 +
arch/riscv/include/asm/sbi.h | 15 ++
arch/riscv/include/uapi/asm/kvm.h | 14 ++
arch/riscv/kernel/Makefile | 1 +
arch/riscv/kernel/paravirt.c | 127 +++++++++++
arch/riscv/kernel/time.c | 3 +
arch/riscv/kvm/Kconfig | 1 +
arch/riscv/kvm/Makefile | 1 +
arch/riscv/kvm/vcpu.c | 74 +++++++
arch/riscv/kvm/vcpu_sbi.c | 4 +
arch/riscv/kvm/vcpu_sbi_sta.c | 199 ++++++++++++++++++
tools/testing/selftests/kvm/Makefile | 3 +-
.../selftests/kvm/include/riscv/processor.h | 40 +++-
.../selftests/kvm/lib/riscv/processor.c | 45 ++++
tools/testing/selftests/kvm/lib/riscv/ucall.c | 26 ---
tools/testing/selftests/kvm/steal_time.c | 100 +++++++++
21 files changed, 685 insertions(+), 37 deletions(-)
create mode 100644 arch/riscv/include/asm/paravirt.h
create mode 100644 arch/riscv/include/asm/paravirt_api_clock.h
create mode 100644 arch/riscv/kernel/paravirt.c
create mode 100644 arch/riscv/kvm/vcpu_sbi_sta.c

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