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@xxxxxxxxxxxxxxxx [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 -- 2.43.0