Provide additional context when an unexpected exception occurs by dumping the relevant Supervisor, Virtual Supervisor (VS), and Hypervisor CSRs, along with the general-purpose registers associated with the trap.
Dumping VS-mode CSRs in addition to host CSRs is beneficial when analysing VS-mode traps. VSCAUSE, VSEPC, VSTVAL, and related VS state are required to properly diagnose unexpected guest traps and potential hypervisor misconfiguration. For example, on an illegal-instruction exception the hardware may record the faulting instruction in VSTVAL. If VSTVAL is zero, VSEPC should always be inspected, and can be used together with objdump to identify the faulting instruction. Dumping VSCAUSE is also useful when the guest does not report it, or when the hypervisor redirects a trap to the guest using VSCAUSE, VSTATUS, and VSTVEC, allowing verification that a subsequent trap is not caused by incorrect VS state. Signed-off-by: Oleksii Kurochko <[email protected]> --- Changes in v3: - Refactor the code dumping of CSRs and GPRs: - Introduce new macros - Re-group some registers when values are displayed. - Print all registers name in lower case. - Drop unnessary "Dumping CSRs", "Dumping GSRs" as it is clear based on names. - Update the commit message: add justification of dumping of some VS* registers. - Drop printing of VSSATP as I don't know usecase for now where it could be needed. --- Changes in v2: - Address coments about print_csr() macros and dump_csrs(). - Add dumping of GPRs pertaining to the trap. --- xen/arch/riscv/traps.c | 69 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 69 insertions(+) diff --git a/xen/arch/riscv/traps.c b/xen/arch/riscv/traps.c index e9c967786312..7b9bcb97035f 100644 --- a/xen/arch/riscv/traps.c +++ b/xen/arch/riscv/traps.c @@ -99,12 +99,81 @@ static const char *decode_cause(unsigned long cause) return decode_trap_cause(cause); } +static void dump_general_regs(const struct cpu_user_regs *regs) +{ +#define GPR_LIST \ + X(regs, ra, " ") X(regs, sp, "\n") \ + X(regs, gp, " ") X(regs, tp, "\n") \ + X(regs, t0, " ") X(regs, t1, "\n") \ + X(regs, t2, " ") X(regs, s0, "\n") \ + X(regs, s1, " ") X(regs, a0, "\n") \ + X(regs, a1, " ") X(regs, a2, "\n") \ + X(regs, a3, " ") X(regs, a4, "\n") \ + X(regs, a5, " ") X(regs, a6, "\n") \ + X(regs, a7, " ") X(regs, s2, "\n") \ + X(regs, s3, " ") X(regs, s4, "\n") \ + X(regs, s5, " ") X(regs, s6, "\n") \ + X(regs, s7, " ") X(regs, s8, "\n") \ + X(regs, s9, " ") X(regs, s10, "\n") \ + X(regs, s11, " ") X(regs, t3, "\n") \ + X(regs, t4, " ") X(regs, t4, "\n") + +#define X(regs, name, delim) \ + printk("\t %-4s: %016lx" delim, #name, (regs)->name); + + GPR_LIST + +#undef X +#undef GPR_LIST +} + +static void dump_csrs(unsigned long cause) +{ +#define CSR_LIST \ + X(stvec, CSR_STVEC, " ") X(vstvec, CSR_VSTVEC, "\n") \ + X(sepc, CSR_SEPC, " ") X(vsepc, CSR_VSEPC, "\n") \ + X(stval, CSR_STVAL, " ") X(vstval, CSR_VSTVAL, "\n") \ + X(status, CSR_SSTATUS, " ") X(vsstatus, CSR_VSSTATUS, "\n") \ + X(satp, CSR_SATP, "\n") \ + X(scause, CSR_SCAUSE, " [%s]\n", \ + decode_cause(v)) \ + X(vscause, CSR_VSCAUSE, " [%s]\n\n", \ + decode_cause(v)) \ + X(hstatus, CSR_HSTATUS, " [%s%s%s%s%s%s ]\n", \ + (v & HSTATUS_VTSR) ? " VTSR" : "", \ + (v & HSTATUS_VTVM) ? " VTVM" : "", \ + (v & HSTATUS_HU) ? " HU" : "", \ + (v & HSTATUS_SPVP) ? " SPVP" : "", \ + (v & HSTATUS_SPV) ? " SPV" : "", \ + (v & HSTATUS_GVA) ? " GVA" : "") \ + X(hgatp, CSR_HGATP, "\n") \ + X(htval, CSR_HTVAL, "\n") \ + X(htinst, CSR_HTINST, "\n") \ + X(hedeleg, CSR_HEDELEG, "\n") \ + X(hideleg, CSR_HIDELEG, "\n") \ + X(hstateen0, CSR_HSTATEEN0, "\n\n") + +#define X(name, csr, fmt, ...) \ +do { \ + unsigned long v = csr_read(csr); \ + printk("\t %-10s: %016lx" fmt, #name, v, ##__VA_ARGS__); \ +} while (0); + + CSR_LIST + +#undef X +#undef CSR_LIST +} + static void do_unexpected_trap(const struct cpu_user_regs *regs) { unsigned long cause = csr_read(CSR_SCAUSE); printk("Unhandled exception: %s\n", decode_cause(cause)); + dump_csrs(cause); + dump_general_regs(regs); + die(); } -- 2.52.0
