On Mon, Mar 27, 2023 at 04:49:30PM +0000, Andy Chiu wrote: > Vector unit is disabled by default for all user processes. Thus, a > process will take a trap (illegal instruction) into kernel at the first > time when it uses Vector. Only after then, the kernel allocates V > context and starts take care of the context for that user process. > > Suggested-by: Richard Henderson <richard.henderson@xxxxxxxxxx> > Link: https://lore.kernel.org/r/3923eeee-e4dc-0911-40bf-84c34aee962d@xxxxxxxxxx > Signed-off-by: Andy Chiu <andy.chiu@xxxxxxxxxx> I see you dropped two R-b from this patch, what actually changed here? It's not immediately obvious to me (sorry!) and the cover doesn't mention why they were dropped. Thanks Andy! Conor. > --- > arch/riscv/include/asm/insn.h | 29 +++++++++++ > arch/riscv/include/asm/vector.h | 2 + > arch/riscv/kernel/traps.c | 26 +++++++++- > arch/riscv/kernel/vector.c | 90 +++++++++++++++++++++++++++++++++ > 4 files changed, 145 insertions(+), 2 deletions(-) > > diff --git a/arch/riscv/include/asm/insn.h b/arch/riscv/include/asm/insn.h > index 8d5c84f2d5ef..4e1505cef8aa 100644 > --- a/arch/riscv/include/asm/insn.h > +++ b/arch/riscv/include/asm/insn.h > @@ -137,6 +137,26 @@ > #define RVG_OPCODE_JALR 0x67 > #define RVG_OPCODE_JAL 0x6f > #define RVG_OPCODE_SYSTEM 0x73 > +#define RVG_SYSTEM_CSR_OFF 20 > +#define RVG_SYSTEM_CSR_MASK GENMASK(12, 0) > + > +/* parts of opcode for RVF, RVD and RVQ */ > +#define RVFDQ_FL_FS_WIDTH_OFF 12 > +#define RVFDQ_FL_FS_WIDTH_MASK GENMASK(3, 0) > +#define RVFDQ_FL_FS_WIDTH_W 2 > +#define RVFDQ_FL_FS_WIDTH_D 3 > +#define RVFDQ_LS_FS_WIDTH_Q 4 > +#define RVFDQ_OPCODE_FL 0x07 > +#define RVFDQ_OPCODE_FS 0x27 > + > +/* parts of opcode for RVV */ > +#define RVV_OPCODE_VECTOR 0x57 > +#define RVV_VL_VS_WIDTH_8 0 > +#define RVV_VL_VS_WIDTH_16 5 > +#define RVV_VL_VS_WIDTH_32 6 > +#define RVV_VL_VS_WIDTH_64 7 > +#define RVV_OPCODE_VL RVFDQ_OPCODE_FL > +#define RVV_OPCODE_VS RVFDQ_OPCODE_FS > > /* parts of opcode for RVC*/ > #define RVC_OPCODE_C0 0x0 > @@ -304,6 +324,15 @@ static __always_inline bool riscv_insn_is_branch(u32 code) > (RVC_X(x_, RVC_B_IMM_7_6_OPOFF, RVC_B_IMM_7_6_MASK) << RVC_B_IMM_7_6_OFF) | \ > (RVC_IMM_SIGN(x_) << RVC_B_IMM_SIGN_OFF); }) > > +#define RVG_EXTRACT_SYSTEM_CSR(x) \ > + ({typeof(x) x_ = (x); RV_X(x_, RVG_SYSTEM_CSR_OFF, RVG_SYSTEM_CSR_MASK); }) > + > +#define RVFDQ_EXTRACT_FL_FS_WIDTH(x) \ > + ({typeof(x) x_ = (x); RV_X(x_, RVFDQ_FL_FS_WIDTH_OFF, \ > + RVFDQ_FL_FS_WIDTH_MASK); }) > + > +#define RVV_EXRACT_VL_VS_WIDTH(x) RVFDQ_EXTRACT_FL_FS_WIDTH(x) > + > /* > * Get the immediate from a J-type instruction. > * > diff --git a/arch/riscv/include/asm/vector.h b/arch/riscv/include/asm/vector.h > index 4161352d6ea8..70a5e696c1de 100644 > --- a/arch/riscv/include/asm/vector.h > +++ b/arch/riscv/include/asm/vector.h > @@ -20,6 +20,7 @@ > > extern unsigned long riscv_v_vsize; > void riscv_v_setup_vsize(void); > +bool riscv_v_first_use_handler(struct pt_regs *regs); > > static __always_inline bool has_vector(void) > { > @@ -163,6 +164,7 @@ static inline void __switch_to_vector(struct task_struct *prev, > struct pt_regs; > > static __always_inline bool has_vector(void) { return false; } > +static inline bool riscv_v_first_use_handler(struct pt_regs *regs) { return false; } > static inline bool riscv_v_vstate_query(struct pt_regs *regs) { return false; } > #define riscv_v_vsize (0) > #define riscv_v_setup_vsize() do {} while (0) > diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c > index 1f4e37be7eb3..f543e5ebfd29 100644 > --- a/arch/riscv/kernel/traps.c > +++ b/arch/riscv/kernel/traps.c > @@ -26,6 +26,7 @@ > #include <asm/ptrace.h> > #include <asm/syscall.h> > #include <asm/thread_info.h> > +#include <asm/vector.h> > > int show_unhandled_signals = 1; > > @@ -145,8 +146,29 @@ DO_ERROR_INFO(do_trap_insn_misaligned, > SIGBUS, BUS_ADRALN, "instruction address misaligned"); > DO_ERROR_INFO(do_trap_insn_fault, > SIGSEGV, SEGV_ACCERR, "instruction access fault"); > -DO_ERROR_INFO(do_trap_insn_illegal, > - SIGILL, ILL_ILLOPC, "illegal instruction"); > + > +asmlinkage __visible __trap_section void do_trap_insn_illegal(struct pt_regs *regs) > +{ > + if (user_mode(regs)) { > + irqentry_enter_from_user_mode(regs); > + > + local_irq_enable(); > + > + if (!has_vector() || !riscv_v_first_use_handler(regs)) > + do_trap_error(regs, SIGILL, ILL_ILLOPC, regs->epc, > + "Oops - illegal instruction"); > + > + irqentry_exit_to_user_mode(regs); > + } else { > + irqentry_state_t state = irqentry_nmi_enter(regs); > + > + do_trap_error(regs, SIGILL, ILL_ILLOPC, regs->epc, > + "Oops - illegal instruction"); > + > + irqentry_nmi_exit(regs, state); > + } > +} > + > DO_ERROR_INFO(do_trap_load_fault, > SIGSEGV, SEGV_ACCERR, "load access fault"); > #ifndef CONFIG_RISCV_M_MODE > diff --git a/arch/riscv/kernel/vector.c b/arch/riscv/kernel/vector.c > index 03582e2ade83..ea59f32adf46 100644 > --- a/arch/riscv/kernel/vector.c > +++ b/arch/riscv/kernel/vector.c > @@ -4,9 +4,19 @@ > * Author: Andy Chiu <andy.chiu@xxxxxxxxxx> > */ > #include <linux/export.h> > +#include <linux/sched/signal.h> > +#include <linux/types.h> > +#include <linux/slab.h> > +#include <linux/sched.h> > +#include <linux/uaccess.h> > > +#include <asm/thread_info.h> > +#include <asm/processor.h> > +#include <asm/insn.h> > #include <asm/vector.h> > #include <asm/csr.h> > +#include <asm/ptrace.h> > +#include <asm/bug.h> > > unsigned long riscv_v_vsize __read_mostly; > EXPORT_SYMBOL_GPL(riscv_v_vsize); > @@ -18,3 +28,83 @@ void riscv_v_setup_vsize(void) > riscv_v_vsize = csr_read(CSR_VLENB) * 32; > riscv_v_disable(); > } > + > +static bool insn_is_vector(u32 insn_buf) > +{ > + u32 opcode = insn_buf & __INSN_OPCODE_MASK; > + bool is_vector = false; > + u32 width, csr; > + > + /* > + * All V-related instructions, including CSR operations are 4-Byte. So, > + * do not handle if the instruction length is not 4-Byte. > + */ > + if (unlikely(GET_INSN_LENGTH(insn_buf) != 4)) > + return false; > + > + switch (opcode) { > + case RVV_OPCODE_VECTOR: > + is_vector = true; > + break; > + case RVV_OPCODE_VL: > + case RVV_OPCODE_VS: > + width = RVV_EXRACT_VL_VS_WIDTH(insn_buf); > + if (width == RVV_VL_VS_WIDTH_8 || width == RVV_VL_VS_WIDTH_16 || > + width == RVV_VL_VS_WIDTH_32 || width == RVV_VL_VS_WIDTH_64) > + is_vector = true; > + break; > + case RVG_OPCODE_SYSTEM: > + csr = RVG_EXTRACT_SYSTEM_CSR(insn_buf); > + if ((csr >= CSR_VSTART && csr <= CSR_VCSR) || > + (csr >= CSR_VL && csr <= CSR_VLENB)) > + is_vector = true; > + break; > + } > + return is_vector; > +} > + > +static int riscv_v_thread_zalloc(void) > +{ > + void *datap; > + > + datap = kzalloc(riscv_v_vsize, GFP_KERNEL); > + if (!datap) > + return -ENOMEM; > + current->thread.vstate.datap = datap; > + memset(¤t->thread.vstate, 0, offsetof(struct __riscv_v_ext_state, > + datap)); > + return 0; > +} > + > +bool riscv_v_first_use_handler(struct pt_regs *regs) > +{ > + u32 __user *epc = (u32 __user *)regs->epc; > + u32 insn = (u32)regs->badaddr; > + > + /* If V has been enabled then it is not the first-use trap */ > + if (riscv_v_vstate_query(regs)) > + return false; > + > + /* Get the instruction */ > + if (!insn) { > + if (__get_user(insn, epc)) > + return false; > + } > + /* Filter out non-V instructions */ > + if (!insn_is_vector(insn)) > + return false; > + > + /* Sanity check. datap should be null by the time of the first-use trap */ > + WARN_ON(current->thread.vstate.datap); > + /* > + * Now we sure that this is a V instruction. And it executes in the > + * context where VS has been off. So, try to allocate the user's V > + * context and resume execution. > + */ > + if (riscv_v_thread_zalloc()) { > + force_sig(SIGKILL); > + return true; > + } > + riscv_v_vstate_on(regs); > + return true; > +} > -- > 2.17.1 >
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