[PATCH v20 00/17] KVM RISC-V Support

From: Anup Patel
Date: Mon Sep 27 2021 - 07:40:51 EST

This series adds initial KVM RISC-V support. Currently, we are able to boot
Linux on RV64/RV32 Guest with multiple VCPUs.

Key aspects of KVM RISC-V added by this series are:
1. No RISC-V specific KVM IOCTL
2. Loadable KVM RISC-V module supported
3. Minimal possible KVM world-switch which touches only GPRs and few CSRs
4. Both RV64 and RV32 host supported
5. Full Guest/VM switch is done via vcpu_get/vcpu_put infrastructure
6. KVM ONE_REG interface for VCPU register access from user-space
7. PLIC emulation is done in user-space
8. Timer and IPI emuation is done in-kernel
9. Both Sv39x4 and Sv48x4 supported for RV64 host
10. MMU notifiers supported
11. Generic dirtylog supported
12. FP lazy save/restore supported
13. SBI v0.1 emulation for KVM Guest available
14. Forward unhandled SBI calls to KVM userspace
15. Hugepage support for Guest/VM
16. IOEVENTFD support for Vhost

Here's a brief TODO list which we will work upon after this series:
1. KVM unit test support
2. KVM selftest support
3. SBI v0.3 emulation in-kernel
4. In-kernel PMU virtualization
5. In-kernel AIA irqchip support
6. Nested virtualizaiton
7. ..... and more .....

This series can be found in riscv_kvm_v20 branch at:

Our work-in-progress KVMTOOL RISC-V port can be found in riscv_v9 branch
at: https//github.com/avpatel/kvmtool.git

The QEMU RISC-V hypervisor emulation is done by Alistair and is available
in master branch at: https://git.qemu.org/git/qemu.git

To play around with KVM RISC-V, refer KVM RISC-V wiki at:

Changes since v19:
- Rebased on Linux-5.15-rc3
- Converted kvm_err() to kvm_debug() in kvm_set_spte_gfn() function
added by PATCH11

Changes since v18:
- Rebased on Linux-5.14-rc3
- Moved to new KVM debugfs interface
- Dropped PATCH17 of v18 series for having KVM RISC-V in drivers/staging

Changes since v17:
- Rebased on Linux-5.13-rc2
- Moved to new KVM MMU notifier APIs
- Removed redundant kvm_arch_vcpu_uninit()
- Moved KVM RISC-V sources to drivers/staging for compliance with
Linux RISC-V patch acceptance policy

Changes since v16:
- Rebased on Linux-5.12-rc5
- Remove redundant kvm_arch_create_memslot(), kvm_arch_vcpu_setup(),
kvm_arch_vcpu_init(), kvm_arch_has_vcpu_debugfs(), and
kvm_arch_create_vcpu_debugfs() from PATCH5
- Make stage2_wp_memory_region() and stage2_ioremap() as static
in PATCH13

Changes since v15:
- Rebased on Linux-5.11-rc3
- Fixed kvm_stage2_map() to use gfn_to_pfn_prot() for determing
writeability of a host pfn.
- Use "__u64" in-place of "u64" and "__u32" in-place of "u32" for

Changes since v14:
- Rebased on Linux-5.10-rc3
- Fixed Stage2 (G-stage) PDG allocation to ensure it is 16KB aligned

Changes since v13:
- Rebased on Linux-5.9-rc3
- Fixed kvm_riscv_vcpu_set_reg_csr() for SIP updation in PATCH5
- Fixed instruction length computation in PATCH7
- Added ioeventfd support in PATCH7
- Ensure HSTATUS.SPVP is set to correct value before using HLV/HSV
intructions in PATCH7
- Fixed stage2_map_page() to set PTE 'A' and 'D' bits correctly
in PATCH10
- Added stage2 dirty page logging in PATCH10
- Allow KVM user-space to SET/GET SCOUNTER CSR in PATCH5
- Save/restore SCOUNTEREN in PATCH6
- Reduced quite a few instructions for __kvm_riscv_switch_to() by
using CSR swap instruction in PATCH6
- Detect and use Sv48x4 when available in PATCH10

Changes since v12:
- Rebased patches on Linux-5.8-rc4
- By default enable all counters in HCOUNTEREN
- RISC-V H-Extension v0.6.1 spec support

Changes since v11:
- Rebased patches on Linux-5.7-rc3
- Fixed typo in typecast of stage2_map_size define
- Introduced struct kvm_cpu_trap to represent trap details and
use it as function parameter wherever applicable
- Pass memslot to kvm_riscv_stage2_map() for supporing dirty page
logging in future
- RISC-V H-Extension v0.6 spec support
- Send-out first three patches as separate series so that it can
be taken by Palmer for Linux RISC-V

Changes since v10:
- Rebased patches on Linux-5.6-rc5
- Reduce RISCV_ISA_EXT_MAX from 256 to 64
- Separate PATCH for removing N-extension related defines
- Added comments as requested by Palmer
- Fixed HIDELEG CSR programming

Changes since v9:
- Rebased patches on Linux-5.5-rc3
- Squash PATCH19 and PATCH20 into PATCH5
- Squash PATCH18 into PATCH11
- Squash PATCH17 into PATCH16
- Added ONE_REG interface for VCPU timer in PATCH13
- Use HTIMEDELTA for VCPU timer in PATCH13
- Updated KVM RISC-V mailing list in MAINTAINERS entry
- Update KVM kconfig option to depend on RISCV_SBI and MMU
- Check for SBI v0.2 and SBI v0.2 RFENCE extension at boot-time
- Use SBI v0.2 RFENCE extension in VMID implementation
- Use SBI v0.2 RFENCE extension in Stage2 MMU implementation
- Use SBI v0.2 RFENCE extension in SBI implementation
- Moved to RISC-V Hypervisor v0.5 draft spec
- Updated Documentation/virt/kvm/api.txt for timer ONE_REG interface

Changes since v8:
- Rebased series on Linux-5.4-rc3 and Atish's SBI v0.2 patches
- Use HRTIMER_MODE_REL instead of HRTIMER_MODE_ABS in timer emulation
- Fixed kvm_riscv_stage2_map() to handle hugepages
- Added patch to forward unhandled SBI calls to user-space
- Added patch for iterative/recursive stage2 page table programming
- Added patch to remove per-CPU vsip_shadow variable
- Added patch to fix race-condition in kvm_riscv_vcpu_sync_interrupts()

Changes since v7:
- Rebased series on Linux-5.4-rc1 and Atish's SBI v0.2 patches
- Removed PATCH1, PATCH3, and PATCH20 because these already merged
- Use kernel doc style comments for ISA bitmap functions
- Don't parse X, Y, and Z extension in riscv_fill_hwcap() because it will
be added in-future
- Mark KVM RISC-V kconfig option as EXPERIMENTAL
- Typo fix in commit description of PATCH6 of v7 series
- Use separate structs for CORE and CSR registers of ONE_REG interface
- Explicitly include asm/sbi.h in kvm/vcpu_sbi.c
- Removed implicit switch-case fall-through in kvm_riscv_vcpu_exit()
- No need to set VSSTATUS.MXR bit in kvm_riscv_vcpu_unpriv_read()
- Removed register for instruction length in kvm_riscv_vcpu_unpriv_read()
- Added defines for checking/decoding instruction length
- Added separate patch to forward unhandled SBI calls to userspace tool

Changes since v6:
- Rebased patches on Linux-5.3-rc7
- Added "return_handled" in struct kvm_mmio_decode to ensure that
kvm_riscv_vcpu_mmio_return() updates SEPC only once
- Removed trap_stval parameter from kvm_riscv_vcpu_unpriv_read()
- Updated git repo URL in MAINTAINERS entry

Changes since v5:
- Update SPEC in kvm_riscv_vcpu_mmio_return() for MMIO exits
- Use switch case instead of illegal instruction opcode table for simplicity
- Improve comments in stage2_remote_tlb_flush() for a potential remote TLB
flush optimization
- Handle all unsupported SBI calls in default case of
kvm_riscv_vcpu_sbi_ecall() function
- Fixed kvm_riscv_vcpu_sync_interrupts() for software interrupts
- Improved unprivilege reads to handle traps due to Guest stage1 page table
- Added separate patch to document RISC-V specific things in

Changes since v4:
- Rebased patches on Linux-5.3-rc5
- Added Paolo's Acked-by and Reviewed-by
- Updated mailing list in MAINTAINERS entry

Changes since v3:
- Moved patch for ISA bitmap from KVM prep series to this series
- Make vsip_shadow as run-time percpu variable instead of compile-time
- Flush Guest TLBs on all Host CPUs whenever we run-out of VMIDs

Changes since v2:
- Removed references of KVM_REQ_IRQ_PENDING from all patches
- Use kvm->srcu within in-kernel KVM run loop
- Added percpu vsip_shadow to track last value programmed in VSIP CSR
- Added comments about irqs_pending and irqs_pending_mask
- Used kvm_arch_vcpu_runnable() in-place-of kvm_riscv_vcpu_has_interrupt()
in system_opcode_insn()
- Removed unwanted smp_wmb() in kvm_riscv_stage2_vmid_update()
- Use kvm_flush_remote_tlbs() in kvm_riscv_stage2_vmid_update()
- Use READ_ONCE() in kvm_riscv_stage2_update_hgatp() for vmid

Changes since v1:
- Fixed compile errors in building KVM RISC-V as module
- Removed unused kvm_riscv_halt_guest() and kvm_riscv_resume_guest()
- Set KVM_CAP_SYNC_MMU capability only after MMU notifiers are implemented
- Made vmid_version as unsigned long instead of atomic
- Renamed kvm_riscv_stage2_update_pgtbl() to kvm_riscv_stage2_update_hgatp()
- Configure HIDELEG and HEDELEG in kvm_arch_hardware_enable()
- Updated ONE_REG interface for CSR access to user-space
- Removed irqs_pending_lock and use atomic bitops instead
- Added separate patch for FP ONE_REG interface
- Added separate patch for updating MAINTAINERS file

Anup Patel (13):
RISC-V: Add hypervisor extension related CSR defines
RISC-V: Add initial skeletal KVM support
RISC-V: KVM: Implement VCPU create, init and destroy functions
RISC-V: KVM: Implement VCPU interrupts and requests handling
RISC-V: KVM: Implement VCPU world-switch
RISC-V: KVM: Handle MMIO exits for VCPU
RISC-V: KVM: Handle WFI exits for VCPU
RISC-V: KVM: Implement VMID allocator
RISC-V: KVM: Implement stage2 page table programming
RISC-V: KVM: Implement MMU notifiers
RISC-V: KVM: Document RISC-V specific parts of KVM API

Atish Patra (4):
RISC-V: KVM: Add timer functionality
RISC-V: KVM: FP lazy save/restore
RISC-V: KVM: Implement ONE REG interface for FP registers
RISC-V: KVM: Add SBI v0.1 support

Documentation/virt/kvm/api.rst | 193 ++++-
arch/riscv/Kconfig | 1 +
arch/riscv/Makefile | 1 +
arch/riscv/include/asm/csr.h | 87 +++
arch/riscv/include/asm/kvm_host.h | 266 +++++++
arch/riscv/include/asm/kvm_types.h | 7 +
arch/riscv/include/asm/kvm_vcpu_timer.h | 44 ++
arch/riscv/include/uapi/asm/kvm.h | 128 +++
arch/riscv/kernel/asm-offsets.c | 156 ++++
arch/riscv/kvm/Kconfig | 36 +
arch/riscv/kvm/Makefile | 25 +
arch/riscv/kvm/main.c | 118 +++
arch/riscv/kvm/mmu.c | 802 +++++++++++++++++++
arch/riscv/kvm/tlb.S | 74 ++
arch/riscv/kvm/vcpu.c | 997 ++++++++++++++++++++++++
arch/riscv/kvm/vcpu_exit.c | 701 +++++++++++++++++
arch/riscv/kvm/vcpu_sbi.c | 185 +++++
arch/riscv/kvm/vcpu_switch.S | 400 ++++++++++
arch/riscv/kvm/vcpu_timer.c | 225 ++++++
arch/riscv/kvm/vm.c | 97 +++
arch/riscv/kvm/vmid.c | 120 +++
drivers/clocksource/timer-riscv.c | 9 +
include/clocksource/timer-riscv.h | 16 +
include/uapi/linux/kvm.h | 8 +
25 files changed, 4699 insertions(+), 9 deletions(-)
create mode 100644 arch/riscv/include/asm/kvm_host.h
create mode 100644 arch/riscv/include/asm/kvm_types.h
create mode 100644 arch/riscv/include/asm/kvm_vcpu_timer.h
create mode 100644 arch/riscv/include/uapi/asm/kvm.h
create mode 100644 arch/riscv/kvm/Kconfig
create mode 100644 arch/riscv/kvm/Makefile
create mode 100644 arch/riscv/kvm/main.c
create mode 100644 arch/riscv/kvm/mmu.c
create mode 100644 arch/riscv/kvm/tlb.S
create mode 100644 arch/riscv/kvm/vcpu.c
create mode 100644 arch/riscv/kvm/vcpu_exit.c
create mode 100644 arch/riscv/kvm/vcpu_sbi.c
create mode 100644 arch/riscv/kvm/vcpu_switch.S
create mode 100644 arch/riscv/kvm/vcpu_timer.c
create mode 100644 arch/riscv/kvm/vm.c
create mode 100644 arch/riscv/kvm/vmid.c
create mode 100644 include/clocksource/timer-riscv.h