[PATCH v1 00/14] RISC-V: Add steal-time support

Andrew Jones
2023-12-05T18:11:44Z

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[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 11-14 - Add RISC-V support to the KVM selftests steal_time
test and the SBI extension regs in the get-reg-list
test.

These patches are based on the make SBI uapi consistent with the ISA
uapi KVM series, which is based on Anup's riscv_kvm_more_exts_v1 branch.
Based-on: 20231130183537.55203-8-ajones@ventanamicro.com

[1] https://github.com/riscv-non-isa/riscv-sbi-doc/blob/master/src/ext-steal-time.adoc

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

Changes since RFC:
- Rebased on v6.7-rc3 (plus the patches mentioned above)
- Added defines for the -1's [Conor]
- Added a comment to the steal read sequence [Conor]
- Only do the steal read sequence for 32-bit and added READ_ONCE's
- Check for SBI v2.0 implementation
- Rename set_steal_time_shmem to steal_time_set_shmem
- Add get-reg-list support and test with get-reg-list kselftest
- A few other minor improvements
- Picked up one r-b from Conor

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: Add support for SBI extension registers
RISC-V: KVM: Add support for SBI STA registers
RISC-V: KVM: Implement SBI STA extension
RISC-V: KVM: selftests: Move sbi_ecall to processor.c
RISC-V: KVM: selftests: Add guest_sbi_probe_extension
RISC-V: KVM: selftests: Add steal_time test support
RISC-V: KVM: selftests: Add get-reg-list test for STA registers

.../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 | 6 +
arch/riscv/include/asm/paravirt.h | 28 +++
arch/riscv/include/asm/paravirt_api_clock.h | 1 +
arch/riscv/include/asm/sbi.h | 17 ++
arch/riscv/include/uapi/asm/kvm.h | 13 ++
arch/riscv/kernel/Makefile | 1 +
arch/riscv/kernel/paravirt.c | 138 ++++++++++++
arch/riscv/kernel/time.c | 3 +
arch/riscv/kvm/Kconfig | 1 +
arch/riscv/kvm/Makefile | 1 +
arch/riscv/kvm/vcpu.c | 7 +
arch/riscv/kvm/vcpu_onereg.c | 105 +++++++++
arch/riscv/kvm/vcpu_sbi.c | 4 +
arch/riscv/kvm/vcpu_sbi_sta.c | 202 ++++++++++++++++++
tools/testing/selftests/kvm/Makefile | 5 +-
.../selftests/kvm/include/riscv/processor.h | 22 ++
.../selftests/kvm/lib/riscv/processor.c | 45 ++++
tools/testing/selftests/kvm/lib/riscv/ucall.c | 26 ---
.../selftests/kvm/riscv/get-reg-list.c | 43 ++++
tools/testing/selftests/kvm/steal_time.c | 99 +++++++++
23 files changed, 770 insertions(+), 31 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