[0/6] riscv: add SBI FWFT misaligned exception delegation support

Message

Clément Léger Jan. 6, 2025, 3:48 p.m. UTC

The SBI Firmware Feature extension allows the S-mode to request some
specific features (either hardware or software) to be enabled. This
series uses this extension to request misaligned access exception
delegation to S-mode in order to let the kernel handle it. It also adds
support for the KVM FWFT SBI extension based on the misaligned access
handling infrastructure.

FWFT SBI extension is part of the SBI V3.0 specifications [1]. It can be
tested using the qemu provided at [2] which contains the series from
[3]. kvm-unit-tests [4] can be used inside kvm to tests the correct
delegation of misaligned exceptions. Upstream OpenSBI can be used.

The test can be run using a small utility[5] as well as using kvm-tools:

$ qemu-system-riscv64 \
	-cpu rv64,trap-misaligned-access=true,v=true \
	-M virt \
	-m 1024M \
	-bios fw_dynamic.bin \
	-kernel Image
 ...

 # ./unaligned
 Buf base address: 0x5555756ff0f0
 Testing emulated misaligned accesses, size 2, offset 1
 Testing non-emulated misaligned accesses, size 2, offset 1
 Testing emulated misaligned accesses, size 4, offset 1
 Testing non-emulated misaligned accesses, size 4, offset 1
 Testing emulated misaligned accesses, size 4, offset 2
 Testing non-emulated misaligned accesses, size 4, offset 2
 Testing emulated misaligned accesses, size 4, offset 3
 Testing non-emulated misaligned accesses, size 4, offset 3
 Testing emulated misaligned accesses, size 8, offset 1
 Testing non-emulated misaligned accesses, size 8, offset 1
 Testing emulated misaligned accesses, size 8, offset 2
 Testing non-emulated misaligned accesses, size 8, offset 2
 Testing emulated misaligned accesses, size 8, offset 3
 Testing non-emulated misaligned accesses, size 8, offset 3
 Testing emulated misaligned accesses, size 8, offset 4
 Testing non-emulated misaligned accesses, size 8, offset 4
 Testing emulated misaligned accesses, size 8, offset 5
 Testing non-emulated misaligned accesses, size 8, offset 5
 Testing emulated misaligned accesses, size 8, offset 6
 Testing non-emulated misaligned accesses, size 8, offset 6
 Testing emulated misaligned accesses, size 8, offset 7
 Testing non-emulated misaligned accesses, size 8, offset 7

 # lkvm run -k sbi.flat -m 128
  Info: # lkvm run -k sbi.flat -m 128 -c 1 --name guest-97
  Info: Removed ghost socket file "/root/.lkvm//guest-97.sock".

 ##########################################################################
 #    kvm-unit-tests
 ##########################################################################

 ... [test messages elided]
 PASS: sbi: fwft: FWFT extension probing no error
 PASS: sbi: fwft: get/set reserved feature 0x6 error == SBI_ERR_DENIED
 PASS: sbi: fwft: get/set reserved feature 0x3fffffff error == SBI_ERR_DENIED
 PASS: sbi: fwft: get/set reserved feature 0x80000000 error == SBI_ERR_DENIED
 PASS: sbi: fwft: get/set reserved feature 0xbfffffff error == SBI_ERR_DENIED
 PASS: sbi: fwft: misaligned_deleg: Get misaligned deleg feature no error
 PASS: sbi: fwft: misaligned_deleg: Set misaligned deleg feature invalid value error
 PASS: sbi: fwft: misaligned_deleg: Set misaligned deleg feature invalid value error
 PASS: sbi: fwft: misaligned_deleg: Set misaligned deleg feature value no error
 PASS: sbi: fwft: misaligned_deleg: Set misaligned deleg feature value 0
 PASS: sbi: fwft: misaligned_deleg: Set misaligned deleg feature value no error
 PASS: sbi: fwft: misaligned_deleg: Set misaligned deleg feature value 1
 PASS: sbi: fwft: misaligned_deleg: Verify misaligned load exception trap in supervisor
 SUMMARY: 50 tests, 2 unexpected failures, 12 skipped

This series is available at [6].

Link: https://github.com/riscv-non-isa/riscv-sbi-doc/releases/download/vv3.0-rc2/riscv-sbi.pdf [1]
Link: https://github.com/rivosinc/qemu/tree/dev/cleger/misaligned [2]
Link: https://lore.kernel.org/all/[e-mail]/T/ [3]
Link: https://github.com/clementleger/kvm-unit-tests/tree/dev/cleger/fwft_v1 [4]
Link: https://github.com/clementleger/unaligned_test [5]
Link: https://github.com/rivosinc/linux/tree/dev/cleger/fwft_v1 [6]
---

Clément Léger (6):
  riscv: add Firmware Feature (FWFT) SBI extensions definitions
  riscv: request misaligned exception delegation from SBI
  RISC-V: KVM: add SBI extension init()/deinit() functions
  RISC-V: KVM: add support for FWFT SBI extension
  riscv: export unaligned_ctl_available() as a GPL symbol
  RISC-V: KVM: add support for SBI_FWFT_MISALIGNED_DELEG

 arch/riscv/include/asm/cpufeature.h        |   1 +
 arch/riscv/include/asm/kvm_host.h          |   4 +
 arch/riscv/include/asm/kvm_vcpu_sbi.h      |  10 +
 arch/riscv/include/asm/kvm_vcpu_sbi_fwft.h |  37 ++++
 arch/riscv/include/asm/sbi.h               |  28 +++
 arch/riscv/include/uapi/asm/kvm.h          |   1 +
 arch/riscv/kernel/traps_misaligned.c       |  61 ++++++
 arch/riscv/kernel/unaligned_access_speed.c |   2 +
 arch/riscv/kvm/Makefile                    |   1 +
 arch/riscv/kvm/vcpu.c                      |   5 +
 arch/riscv/kvm/vcpu_sbi.c                  |  35 +++-
 arch/riscv/kvm/vcpu_sbi_fwft.c             | 215 +++++++++++++++++++++
 12 files changed, 399 insertions(+), 1 deletion(-)
 create mode 100644 arch/riscv/include/asm/kvm_vcpu_sbi_fwft.h
 create mode 100644 arch/riscv/kvm/vcpu_sbi_fwft.c