[PATCH v4 0/7] lib: sbi: add Ssdbltrp and Smdbltrp ISA extensions
Anup Patel
anup at brainfault.org
Fri Oct 25 11:36:38 PDT 2024
On Fri, Oct 18, 2024 at 2:22 PM Clément Léger <cleger at rivosinc.com> wrote:
>
> A double trap typically arises during a sensitive phase in trap handling
> operations when an exception or interrupt occurs while the trap
> handler (the component responsible for managing these events) is in a
> non-reentrant state. This non-reentrancy usually occurs in the early
> phase of trap handling, wherein the trap handler has not yet preserved
> the necessary state to handle and resume from the trap. The occurrence
> of such event is unlikely but can happen when dealing with hardware
> errors.
>
> This series adds support for Ssdbltrp and Smdbltrp ratified ISA
> extensions [1].
>
> Ssdbltrp can be tested using qemu[2], opensbi[3], linux[4] and
> kvm-unit-tests[5]. Assuming you have a riscv environment available and
> configured (CROSS_COMPILE), it can be built for riscv64 using the
> following instructions:
>
> Qemu:
> $ git clone https://github.com/rivosinc/qemu.git
> $ cd qemu
> $ git switch -C dbltrp_v4 dev/cleger/dbltrp_v4
> $ mkdir build && cd build
> $ ../configure --target-list=riscv64-softmmu
> $ make
>
> OpenSBI:
> $ git clone https://github.com/rivosinc/opensbi.git
> $ cd opensbi
> $ git switch -C dbltrp_v4 dev/cleger/dbltrp_v4
> $ make O=build PLATFORM_RISCV_XLEN=64 PLATFORM=generic
>
> Linux:
> $ git clone https://github.com/rivosinc/linux.git
> $ cd linux
> $ git switch -C dbltrp_v1 dev/cleger/dbltrp_v1
> $ export ARCH=riscv
> $ make O=build defconfig
> $ ./script/config --file build/.config --enable RISCV_DBLTRP
> $ make O=build
>
> kvm-unit-tests:
> $ git clone https://github.com/clementleger/kvm-unit-tests.git
> $ cd kvm-unit-tests
> $ git switch -C dbltrp_v1 dev/cleger/dbltrp_v1
> $ ./configure --arch=riscv64 --cross-prefix=$CROSS_COMPILE
> $ make
>
> You will also need kvmtool in your rootfs.
>
> Run with kvm-unit-test test as kernel:
> $ qemu-system-riscv64 \
> -M virt \
> -cpu rv64,ssdbltrp=true,smdbltrp=true \
> -nographic \
> -serial mon:stdio \
> -bios opensbi/build/platform/generic/firmware/fw_jump.bin \
> -kernel kvm-unit-tests-dbltrp/riscv/sbi_dbltrp.flat
> ...
> [OpenSBI boot partially elided]
> Boot HART ISA Extensions : sscofpmf,sstc,zicntr,zihpm,zicboz,zicbom,sdtrig,svadu,ssdbltrp
> ...
> ##########################################################################
> # kvm-unit-tests
> ##########################################################################
>
> PASS: sbi: fwft: FWFT extension probing no error
> PASS: sbi: fwft: FWFT extension is present
> PASS: sbi: fwft: dbltrp: Get double trap enable feature value
> PASS: sbi: fwft: dbltrp: Set double trap enable feature value == 0
> PASS: sbi: fwft: dbltrp: Get double trap enable feature value == 0
> PASS: sbi: fwft: dbltrp: Double trap disabled, trap first time ok
> PASS: sbi: fwft: dbltrp: Set double trap enable feature value == 1
> PASS: sbi: fwft: dbltrp: Get double trap enable feature value == 1
> PASS: sbi: fwft: dbltrp: Trapped twice allowed ok
> INFO: sbi: fwft: dbltrp: Should generate a double trap and crash !
>
> sbi_trap_error: hart0: trap0: double trap handler failed (error -10)
>
> sbi_trap_error: hart0: trap0: mcause=0x0000000000000010 mtval=0x0000000000000000
> sbi_trap_error: hart0: trap0: mtval2=0x0000000000000003 mtinst=0x0000000000000000
> sbi_trap_error: hart0: trap0: mepc=0x00000000802000d8 mstatus=0x8000000a01006900
> sbi_trap_error: hart0: trap0: ra=0x00000000802001fc sp=0x0000000080213e70
> sbi_trap_error: hart0: trap0: gp=0x0000000000000000 tp=0x0000000080088000
> sbi_trap_error: hart0: trap0: s0=0x0000000080213e80 s1=0x0000000000000001
> sbi_trap_error: hart0: trap0: a0=0x0000000080213e80 a1=0x0000000080208193
> sbi_trap_error: hart0: trap0: a2=0x000000008020dc20 a3=0x000000000000000f
> sbi_trap_error: hart0: trap0: a4=0x0000000080210cd8 a5=0x00000000802110d0
> sbi_trap_error: hart0: trap0: a6=0x00000000802136e4 a7=0x0000000046574654
> sbi_trap_error: hart0: trap0: s2=0x0000000080210cd9 s3=0x0000000000000000
> sbi_trap_error: hart0: trap0: s4=0x0000000000000000 s5=0x0000000000000000
> sbi_trap_error: hart0: trap0: s6=0x0000000000000000 s7=0x0000000000000001
> sbi_trap_error: hart0: trap0: s8=0x0000000000002000 s9=0x0000000080083700
> sbi_trap_error: hart0: trap0: s10=0x0000000000000000 s11=0x0000000000000000
> sbi_trap_error: hart0: trap0: t0=0x0000000000000000 t1=0x0000000080213ed8
> sbi_trap_error: hart0: trap0: t2=0x0000000000001000 t3=0x0000000080213ee0
> sbi_trap_error: hart0: trap0: t4=0x0000000000000000 t5=0x000000008020f8d0
> sbi_trap_error: hart0: trap0: t6=0x0000000000000000
>
> Run with linux and kvm-unit-test test in kvm (testing VS-mode):
> $ qemu-system-riscv64 \
> -M virt \
> -cpu rv64,ssdbltrp=true,smdbltrp=true \
> -nographic \
> -serial mon:stdio \
> -bios opensbi/build/platform/generic/firmware/fw_jump.bin \
> -kernel linux/build/arch/riscv/boot/Image
> ...
> [Linux boot partially elided]
> [ 0.735079] riscv-dbltrp: Double trap handling registered
> ...
>
> $ lkvm run -k sbi_dbltrp.flat -m 128 -c 2
> ##########################################################################
> # kvm-unit-tests
> ##########################################################################
>
> PASS: sbi: fwft: FWFT extension probing no error
> PASS: sbi: fwft: FWFT extension is present
> PASS: sbi: fwft: dbltrp: Get double trap enable feature value
> PASS: sbi: fwft: dbltrp: Set double trap enable feature value == 0
> PASS: sbi: fwft: dbltrp: Get double trap enable feature value == 0
> PASS: sbi: fwft: dbltrp: Double trap disabled, trap first time ok
> PASS: sbi: fwft: dbltrp: Set double trap enable feature value == 1
> PASS: sbi: fwft: dbltrp: Get double trap enable feature value == 1
> PASS: sbi: fwft: dbltrp: Trapped twice allowed ok
> INFO: sbi: fwft: dbltrp: Should generate a double trap and crash !
> [ 51.939077] Guest double trap
> [ 51.939323] kvm [93]: VCPU exit error -95
> [ 51.939683] kvm [93]: SEPC=0x802000d8 SSTATUS=0x200004520 HSTATUS=0x200200180
> [ 51.939947] kvm [93]: SCAUSE=0x10 STVAL=0x0 HTVAL=0x3 HTINST=0x0
> KVM_RUN failed: Operation not supported
> $
>
> Testing Smbdbltrp can be done using gdb and trigger some trap. For
> instance, interrupt M-mode firmware at some point, set mstatus.mdt = 1
> and corrupt some register to generate a NULL pointer exception.
>
> Link: https://github.com/riscv/riscv-isa-manual/commit/52a5742d5ab5a0792019033631b2035a493ad981 [1]
> Link: https://github.com/rivosinc/qemu/tree/dev/cleger/dbltrp_v4 [2]
> Link: https://github.com/rivosinc/opensbi/tree/dev/cleger/dbltrp_v4 [3]
> Link: https://github.com/rivosinc/linux/tree/dev/cleger/dbltrp_v1 [4]
> Link: https://github.com/clementleger/kvm-unit-tests/tree/dev/cleger/dbltrp_v1 [5]
>
> ---
> V4:
> - Rebased on master
> - Move mstatusH restoration before mstatus since it contains MDT bit
> - Factorize landing pad/shadow stack menvcfg usage in fwft
>
> V3:
> - Added Samuel Reviewed-by and fix some minor comments
>
> V2:
> - Add check for riscv_len inside CLEAR_MDT macro
> - Order fwft entries by id order
> - Move menvcfg generic access function to the top of sbi_fwft.c file
> - Split SSE event support
> - Add an additional MDT clear after MTVEC is set for all harts
>
> Clément Léger (7):
> lib: sbi: factorize previous virtualization mode read from regs
> lib: sbi: factorize previous mode computation
> lib: sbi: add Ssdbltrp ISA extension support
> lib: sbi: send a double trap SSE event to supervisor
> lib: sbi: fwft: factorize menvcfg read/write
> lib: sbi: implement firmware feature SBI_FWFT_DOUBLE_TRAP
> lib: sbi: add Smdbltrp ISA extension support
Applied this series to the riscv/opensbi repo.
Thanks,
Anup
>
> firmware/fw_base.S | 37 ++++++++--
> include/sbi/riscv_encoding.h | 18 +++--
> include/sbi/sbi_ecall_interface.h | 1 +
> include/sbi/sbi_hart.h | 2 +
> include/sbi/sbi_trap.h | 14 ++++
> include/sbi/sbi_trap_ldst.h | 2 +
> lib/sbi/objects.mk | 1 +
> lib/sbi/sbi_double_trap.c | 30 ++++++++
> lib/sbi/sbi_emulate_csr.c | 16 +---
> lib/sbi/sbi_fwft.c | 119 ++++++++++++++++--------------
> lib/sbi/sbi_hart.c | 4 +
> lib/sbi/sbi_illegal_insn.c | 2 +-
> lib/sbi/sbi_sse.c | 1 +
> lib/sbi/sbi_system.c | 2 +-
> lib/sbi/sbi_trap.c | 14 ++--
> lib/sbi/sbi_trap_ldst.c | 4 +-
> 16 files changed, 180 insertions(+), 87 deletions(-)
> create mode 100644 lib/sbi/sbi_double_trap.c
>
> --
> 2.45.2
>
>
> --
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