riscv: Allocate user's vector context in the first-use trap

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@linaro.org>
Link: https://lore.kernel.org/r/3923eeee-e4dc-0911-40bf-84c34aee962d@linaro.org
Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230605110724.21391-12-andy.chiu@sifive.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
This commit is contained in:
Andy Chiu 2023-06-05 11:07:08 +00:00 committed by Palmer Dabbelt
parent 3a2df6323d
commit cd05483724
No known key found for this signature in database
GPG Key ID: 2E1319F35FBB1889
4 changed files with 150 additions and 2 deletions

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@ -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.
*

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@ -21,6 +21,7 @@
extern unsigned long riscv_v_vsize;
int riscv_v_setup_vsize(void);
bool riscv_v_first_use_handler(struct pt_regs *regs);
static __always_inline bool has_vector(void)
{
@ -165,6 +166,7 @@ struct pt_regs;
static inline int riscv_v_setup_vsize(void) { return -EOPNOTSUPP; }
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_vstate_save(task, regs) do {} while (0)

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@ -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 (!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

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@ -4,10 +4,19 @@
* Author: Andy Chiu <andy.chiu@sifive.com>
*/
#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/elf.h>
#include <asm/ptrace.h>
#include <asm/bug.h>
unsigned long riscv_v_vsize __read_mostly;
@ -34,3 +43,89 @@ int riscv_v_setup_vsize(void)
return 0;
}
static bool insn_is_vector(u32 insn_buf)
{
u32 opcode = insn_buf & __INSN_OPCODE_MASK;
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:
return true;
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)
return 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))
return true;
}
return false;
}
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(&current->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;
/* Do not handle if V is not supported, or disabled */
if (!(ELF_HWCAP & COMPAT_HWCAP_ISA_V))
return false;
/* 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(SIGBUS);
return true;
}
riscv_v_vstate_on(regs);
return true;
}