[PATCH v4 09/13] riscv: vector: Support xtheadvector save/restore

Charlie Jenkins
2024-07-03T05:57:25Z

Use alternatives to add support for xtheadvector vector save/restore
routines.

Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
---
arch/riscv/include/asm/csr.h | 6 +
arch/riscv/include/asm/switch_to.h | 2 +-
arch/riscv/include/asm/vector.h | 224 +++++++++++++++++++++++++--------
arch/riscv/kernel/cpufeature.c | 2 +-
arch/riscv/kernel/kernel_mode_vector.c | 8 +-
arch/riscv/kernel/process.c | 4 +-
arch/riscv/kernel/signal.c | 6 +-
arch/riscv/kernel/vector.c | 13 +-
8 files changed, 197 insertions(+), 68 deletions(-)

diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
index c0a60c4ed911..b4b3fcb1d142 100644
--- a/arch/riscv/include/asm/csr.h
+++ b/arch/riscv/include/asm/csr.h
@@ -30,6 +30,12 @@
#define SR_VS_CLEAN _AC(0x00000400, UL)
#define SR_VS_DIRTY _AC(0x00000600, UL)

+#define SR_VS_THEAD _AC(0x01800000, UL) /* xtheadvector Status */
+#define SR_VS_OFF_THEAD _AC(0x00000000, UL)
+#define SR_VS_INITIAL_THEAD _AC(0x00800000, UL)
+#define SR_VS_CLEAN_THEAD _AC(0x01000000, UL)
+#define SR_VS_DIRTY_THEAD _AC(0x01800000, UL)
+
#define SR_XS _AC(0x00018000, UL) /* Extension Status */
#define SR_XS_OFF _AC(0x00000000, UL)
#define SR_XS_INITIAL _AC(0x00008000, UL)
diff --git a/arch/riscv/include/asm/switch_to.h b/arch/riscv/include/asm/switch_to.h
index 7594df37cc9f..f9cbebe372b8 100644
--- a/arch/riscv/include/asm/switch_to.h
+++ b/arch/riscv/include/asm/switch_to.h
@@ -99,7 +99,7 @@ do { \
__set_prev_cpu(__prev->thread); \
if (has_fpu()) \
__switch_to_fpu(__prev, __next); \
- if (has_vector()) \
+ if (has_vector() || has_xtheadvector()) \
__switch_to_vector(__prev, __next); \
if (switch_to_should_flush_icache(__next)) \
local_flush_icache_all(); \
diff --git a/arch/riscv/include/asm/vector.h b/arch/riscv/include/asm/vector.h
index 731dcd0ed4de..0425a0d609f9 100644
--- a/arch/riscv/include/asm/vector.h
+++ b/arch/riscv/include/asm/vector.h
@@ -18,6 +18,27 @@
#include <asm/cpufeature.h>
#include <asm/csr.h>
#include <asm/asm.h>
+#include <asm/vendorid_list.h>
+#include <asm/vendor_extensions.h>
+#include <asm/vendor_extensions/thead.h>
+
+#define __riscv_v_vstate_or(_val, TYPE) ({ \
+ typeof(_val) _res = _val; \
+ if (has_xtheadvector()) \
+ _res = (_res & ~SR_VS_THEAD) | SR_VS_##TYPE##_THEAD; \
+ else \
+ _res = (_res & ~SR_VS) | SR_VS_##TYPE; \
+ _res; \
+})
+
+#define __riscv_v_vstate_check(_val, TYPE) ({ \
+ bool _res; \
+ if (has_xtheadvector()) \
+ _res = ((_val) & SR_VS_THEAD) == SR_VS_##TYPE##_THEAD; \
+ else \
+ _res = ((_val) & SR_VS) == SR_VS_##TYPE; \
+ _res; \
+})

extern unsigned long riscv_v_vsize;
int riscv_v_setup_vsize(void);
@@ -40,39 +61,62 @@ static __always_inline bool has_vector(void)
return riscv_has_extension_unlikely(RISCV_ISA_EXT_v);
}

+static __always_inline bool has_xtheadvector_no_alternatives(void)
+{
+ if (IS_ENABLED(CONFIG_RISCV_ISA_XTHEADVECTOR))
+ return riscv_isa_vendor_extension_available(THEAD_VENDOR_ID, XTHEADVECTOR);
+ else
+ return false;
+}
+
+static __always_inline bool has_xtheadvector(void)
+{
+ if (IS_ENABLED(CONFIG_RISCV_ISA_XTHEADVECTOR))
+ return riscv_has_vendor_extension_unlikely(THEAD_VENDOR_ID,
+ RISCV_ISA_VENDOR_EXT_XTHEADVECTOR);
+ else
+ return false;
+}
+
static inline void __riscv_v_vstate_clean(struct pt_regs *regs)
{
- regs->status = (regs->status & ~SR_VS) | SR_VS_CLEAN;
+ regs->status = __riscv_v_vstate_or(regs->status, CLEAN);
}

static inline void __riscv_v_vstate_dirty(struct pt_regs *regs)
{
- regs->status = (regs->status & ~SR_VS) | SR_VS_DIRTY;
+ regs->status = __riscv_v_vstate_or(regs->status, DIRTY);
}

static inline void riscv_v_vstate_off(struct pt_regs *regs)
{
- regs->status = (regs->status & ~SR_VS) | SR_VS_OFF;
+ regs->status = __riscv_v_vstate_or(regs->status, OFF);
}

static inline void riscv_v_vstate_on(struct pt_regs *regs)
{
- regs->status = (regs->status & ~SR_VS) | SR_VS_INITIAL;
+ regs->status = __riscv_v_vstate_or(regs->status, INITIAL);
}

static inline bool riscv_v_vstate_query(struct pt_regs *regs)
{
- return (regs->status & SR_VS) != 0;
+ return !__riscv_v_vstate_check(regs->status, OFF);
}

static __always_inline void riscv_v_enable(void)
{
- csr_set(CSR_SSTATUS, SR_VS);
+ if (has_xtheadvector())
+ csr_set(CSR_SSTATUS, SR_VS_THEAD);
+ else
+ csr_set(CSR_SSTATUS, SR_VS);
}

static __always_inline void riscv_v_disable(void)
{
- csr_clear(CSR_SSTATUS, SR_VS);
+ if (has_xtheadvector())
+ csr_clear(CSR_SSTATUS, SR_VS_THEAD);
+ else
+ csr_clear(CSR_SSTATUS, SR_VS);
}

static __always_inline void __vstate_csr_save(struct __riscv_v_ext_state *dest)
@@ -81,10 +125,36 @@ static __always_inline void __vstate_csr_save(struct __riscv_v_ext_state *dest)
"csrr %0, " __stringify(CSR_VSTART) "\n\t"
"csrr %1, " __stringify(CSR_VTYPE) "\n\t"
"csrr %2, " __stringify(CSR_VL) "\n\t"
- "csrr %3, " __stringify(CSR_VCSR) "\n\t"
- "csrr %4, " __stringify(CSR_VLENB) "\n\t"
: "=r" (dest->vstart), "=r" (dest->vtype), "=r" (dest->vl),
- "=r" (dest->vcsr), "=r" (dest->vlenb) : :);
+ "=r" (dest->vcsr) : :);
+
+ if (has_xtheadvector()) {
+ unsigned long status;
+
+ /*
+ * CSR_VCSR is defined as
+ * [2:1] - vxrm[1:0]
+ * [0] - vxsat
+ * The earlier vector spec implemented by T-Head uses separate
+ * registers for the same bit-elements, so just combine those
+ * into the existing output field.
+ *
+ * Additionally T-Head cores need FS to be enabled when accessing
+ * the VXRM and VXSAT CSRs, otherwise ending in illegal instructions.
+ * Though the cores do not implement the VXRM and VXSAT fields in the
+ * FCSR CSR that vector-0.7.1 specifies.
+ */
+ status = csr_read_set(CSR_STATUS, SR_FS_DIRTY);
+ dest->vcsr = csr_read(CSR_VXSAT) | csr_read(CSR_VXRM) << CSR_VXRM_SHIFT;
+
+ dest->vlenb = riscv_v_vsize / 32;
+
+ if ((status & SR_FS) != SR_FS_DIRTY)
+ csr_write(CSR_STATUS, status);
+ } else {
+ dest->vcsr = csr_read(CSR_VCSR);
+ dest->vlenb = csr_read(CSR_VLENB);
+ }
}

static __always_inline void __vstate_csr_restore(struct __riscv_v_ext_state *src)
@@ -95,9 +165,25 @@ static __always_inline void __vstate_csr_restore(struct __riscv_v_ext_state *src
"vsetvl x0, %2, %1\n\t"
".option pop\n\t"
"csrw " __stringify(CSR_VSTART) ", %0\n\t"
- "csrw " __stringify(CSR_VCSR) ", %3\n\t"
- : : "r" (src->vstart), "r" (src->vtype), "r" (src->vl),
- "r" (src->vcsr) :);
+ : : "r" (src->vstart), "r" (src->vtype), "r" (src->vl));
+
+ if (has_xtheadvector()) {
+ unsigned long status = csr_read(CSR_SSTATUS);
+
+ /*
+ * Similar to __vstate_csr_save above, restore values for the
+ * separate VXRM and VXSAT CSRs from the vcsr variable.
+ */
+ status = csr_read_set(CSR_STATUS, SR_FS_DIRTY);
+
+ csr_write(CSR_VXRM, (src->vcsr >> CSR_VXRM_SHIFT) & CSR_VXRM_MASK);
+ csr_write(CSR_VXSAT, src->vcsr & CSR_VXSAT_MASK);
+
+ if ((status & SR_FS) != SR_FS_DIRTY)
+ csr_write(CSR_STATUS, status);
+ } else {
+ csr_write(CSR_VCSR, src->vcsr);
+ }
}

static inline void __riscv_v_vstate_save(struct __riscv_v_ext_state *save_to,
@@ -107,19 +193,33 @@ static inline void __riscv_v_vstate_save(struct __riscv_v_ext_state *save_to,

riscv_v_enable();
__vstate_csr_save(save_to);
- asm volatile (
- ".option push\n\t"
- ".option arch, +v\n\t"
- "vsetvli %0, x0, e8, m8, ta, ma\n\t"
- "vse8.v v0, (%1)\n\t"
- "add %1, %1, %0\n\t"
- "vse8.v v8, (%1)\n\t"
- "add %1, %1, %0\n\t"
- "vse8.v v16, (%1)\n\t"
- "add %1, %1, %0\n\t"
- "vse8.v v24, (%1)\n\t"
- ".option pop\n\t"
- : "=&r" (vl) : "r" (datap) : "memory");
+ if (has_xtheadvector()) {
+ asm volatile (
+ "mv t0, %0\n\t"
+ THEAD_VSETVLI_T4X0E8M8D1
+ THEAD_VSB_V_V0T0
+ "add t0, t0, t4\n\t"
+ THEAD_VSB_V_V0T0
+ "add t0, t0, t4\n\t"
+ THEAD_VSB_V_V0T0
+ "add t0, t0, t4\n\t"
+ THEAD_VSB_V_V0T0
+ : : "r" (datap) : "memory", "t0", "t4");
+ } else {
+ asm volatile (
+ ".option push\n\t"
+ ".option arch, +v\n\t"
+ "vsetvli %0, x0, e8, m8, ta, ma\n\t"
+ "vse8.v v0, (%1)\n\t"
+ "add %1, %1, %0\n\t"
+ "vse8.v v8, (%1)\n\t"
+ "add %1, %1, %0\n\t"
+ "vse8.v v16, (%1)\n\t"
+ "add %1, %1, %0\n\t"
+ "vse8.v v24, (%1)\n\t"
+ ".option pop\n\t"
+ : "=&r" (vl) : "r" (datap) : "memory");
+ }
riscv_v_disable();
}

@@ -129,55 +229,77 @@ static inline void __riscv_v_vstate_restore(struct __riscv_v_ext_state *restore_
unsigned long vl;

riscv_v_enable();
- asm volatile (
- ".option push\n\t"
- ".option arch, +v\n\t"
- "vsetvli %0, x0, e8, m8, ta, ma\n\t"
- "vle8.v v0, (%1)\n\t"
- "add %1, %1, %0\n\t"
- "vle8.v v8, (%1)\n\t"
- "add %1, %1, %0\n\t"
- "vle8.v v16, (%1)\n\t"
- "add %1, %1, %0\n\t"
- "vle8.v v24, (%1)\n\t"
- ".option pop\n\t"
- : "=&r" (vl) : "r" (datap) : "memory");
+ if (has_xtheadvector()) {
+ asm volatile (
+ "mv t0, %0\n\t"
+ THEAD_VSETVLI_T4X0E8M8D1
+ THEAD_VLB_V_V0T0
+ "add t0, t0, t4\n\t"
+ THEAD_VLB_V_V0T0
+ "add t0, t0, t4\n\t"
+ THEAD_VLB_V_V0T0
+ "add t0, t0, t4\n\t"
+ THEAD_VLB_V_V0T0
+ : : "r" (datap) : "memory", "t0", "t4");
+ } else {
+ asm volatile (
+ ".option push\n\t"
+ ".option arch, +v\n\t"
+ "vsetvli %0, x0, e8, m8, ta, ma\n\t"
+ "vle8.v v0, (%1)\n\t"
+ "add %1, %1, %0\n\t"
+ "vle8.v v8, (%1)\n\t"
+ "add %1, %1, %0\n\t"
+ "vle8.v v16, (%1)\n\t"
+ "add %1, %1, %0\n\t"
+ "vle8.v v24, (%1)\n\t"
+ ".option pop\n\t"
+ : "=&r" (vl) : "r" (datap) : "memory");
+ }
__vstate_csr_restore(restore_from);
riscv_v_disable();
}

static inline void __riscv_v_vstate_discard(void)
{
- unsigned long vl, vtype_inval = 1UL << (BITS_PER_LONG - 1);
+ unsigned long vtype_inval = 1UL << (BITS_PER_LONG - 1);

riscv_v_enable();
+ if (has_xtheadvector())
+ asm volatile (THEAD_VSETVLI_X0X0E8M8D1);
+ else
+ asm volatile (
+ ".option push\n\t"
+ ".option arch, +v\n\t"
+ "vsetvli x0, x0, e8, m8, ta, ma\n\t"
+ ".option pop\n\t");
+
asm volatile (
".option push\n\t"
".option arch, +v\n\t"
- "vsetvli %0, x0, e8, m8, ta, ma\n\t"
"vmv.v.i v0, -1\n\t"
"vmv.v.i v8, -1\n\t"
"vmv.v.i v16, -1\n\t"
"vmv.v.i v24, -1\n\t"
- "vsetvl %0, x0, %1\n\t"
+ "vsetvl x0, x0, %0\n\t"
".option pop\n\t"
- : "=&r" (vl) : "r" (vtype_inval) : "memory");
+ : : "r" (vtype_inval));
+
riscv_v_disable();
}

static inline void riscv_v_vstate_discard(struct pt_regs *regs)
{
- if ((regs->status & SR_VS) == SR_VS_OFF)
- return;
-
- __riscv_v_vstate_discard();
- __riscv_v_vstate_dirty(regs);
+ if (riscv_v_vstate_query(regs)) {
+ __riscv_v_vstate_discard();
+ __riscv_v_vstate_dirty(regs);
+ }
}

static inline void riscv_v_vstate_save(struct __riscv_v_ext_state *vstate,
struct pt_regs *regs)
{
- if ((regs->status & SR_VS) == SR_VS_DIRTY) {
+ if (__riscv_v_vstate_check(regs->status, DIRTY)) {
__riscv_v_vstate_save(vstate, vstate->datap);
__riscv_v_vstate_clean(regs);
}
@@ -186,7 +308,7 @@ static inline void riscv_v_vstate_save(struct __riscv_v_ext_state *vstate,
static inline void riscv_v_vstate_restore(struct __riscv_v_ext_state *vstate,
struct pt_regs *regs)
{
- if ((regs->status & SR_VS) != SR_VS_OFF) {
+ if (riscv_v_vstate_query(regs)) {
__riscv_v_vstate_restore(vstate, vstate->datap);
__riscv_v_vstate_clean(regs);
}
@@ -195,7 +317,7 @@ static inline void riscv_v_vstate_restore(struct __riscv_v_ext_state *vstate,
static inline void riscv_v_vstate_set_restore(struct task_struct *task,
struct pt_regs *regs)
{
- if ((regs->status & SR_VS) != SR_VS_OFF) {
+ if (riscv_v_vstate_query(regs)) {
set_tsk_thread_flag(task, TIF_RISCV_V_DEFER_RESTORE);
riscv_v_vstate_on(regs);
}
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index 077be4ab1f9a..180f7eae9086 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -789,7 +789,7 @@ void __init riscv_fill_hwcap(void)
elf_hwcap &= ~COMPAT_HWCAP_ISA_F;
}

- if (elf_hwcap & COMPAT_HWCAP_ISA_V) {
+ if (elf_hwcap & COMPAT_HWCAP_ISA_V || has_xtheadvector_no_alternatives()) {
riscv_v_setup_vsize();
/*
* ISA string in device tree might have 'v' flag, but
diff --git a/arch/riscv/kernel/kernel_mode_vector.c b/arch/riscv/kernel/kernel_mode_vector.c
index 6afe80c7f03a..99972a48e86b 100644
--- a/arch/riscv/kernel/kernel_mode_vector.c
+++ b/arch/riscv/kernel/kernel_mode_vector.c
@@ -143,7 +143,7 @@ static int riscv_v_start_kernel_context(bool *is_nested)

/* Transfer the ownership of V from user to kernel, then save */
riscv_v_start(RISCV_PREEMPT_V | RISCV_PREEMPT_V_DIRTY);
- if ((task_pt_regs(current)->status & SR_VS) == SR_VS_DIRTY) {
+ if (__riscv_v_vstate_check(task_pt_regs(current)->status, DIRTY)) {
uvstate = &current->thread.vstate;
__riscv_v_vstate_save(uvstate, uvstate->datap);
}
@@ -160,7 +160,7 @@ asmlinkage void riscv_v_context_nesting_start(struct pt_regs *regs)
return;

depth = riscv_v_ctx_get_depth();
- if (depth == 0 && (regs->status & SR_VS) == SR_VS_DIRTY)
+ if (depth == 0 && __riscv_v_vstate_check(regs->status, DIRTY))
riscv_preempt_v_set_dirty();

riscv_v_ctx_depth_inc();
@@ -208,7 +208,7 @@ void kernel_vector_begin(void)
{
bool nested = false;

- if (WARN_ON(!has_vector()))
+ if (WARN_ON(!(has_vector() || has_xtheadvector())))
return;

BUG_ON(!may_use_simd());
@@ -236,7 +236,7 @@ EXPORT_SYMBOL_GPL(kernel_vector_begin);
*/
void kernel_vector_end(void)
{
- if (WARN_ON(!has_vector()))
+ if (WARN_ON(!(has_vector() || has_xtheadvector())))
return;

riscv_v_disable();
diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
index e4bc61c4e58a..191023decd16 100644
--- a/arch/riscv/kernel/process.c
+++ b/arch/riscv/kernel/process.c
@@ -176,7 +176,7 @@ void flush_thread(void)
void arch_release_task_struct(struct task_struct *tsk)
{
/* Free the vector context of datap. */
- if (has_vector())
+ if (has_vector() || has_xtheadvector())
riscv_v_thread_free(tsk);
}

@@ -222,7 +222,7 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
p->thread.s[0] = 0;
}
p->thread.riscv_v_flags = 0;
- if (has_vector())
+ if (has_vector() || has_xtheadvector())
riscv_v_thread_alloc(p);
p->thread.ra = (unsigned long)ret_from_fork;
p->thread.sp = (unsigned long)childregs; /* kernel sp */
diff --git a/arch/riscv/kernel/signal.c b/arch/riscv/kernel/signal.c
index 5a2edd7f027e..1d5e4b3ca9e1 100644
--- a/arch/riscv/kernel/signal.c
+++ b/arch/riscv/kernel/signal.c
@@ -189,7 +189,7 @@ static long restore_sigcontext(struct pt_regs *regs,

return 0;
case RISCV_V_MAGIC:
- if (!has_vector() || !riscv_v_vstate_query(regs) ||
+ if (!(has_vector() || has_xtheadvector()) || !riscv_v_vstate_query(regs) ||
size != riscv_v_sc_size)
return -EINVAL;

@@ -211,7 +211,7 @@ static size_t get_rt_frame_size(bool cal_all)

frame_size = sizeof(*frame);

- if (has_vector()) {
+ if (has_vector() || has_xtheadvector()) {
if (cal_all || riscv_v_vstate_query(task_pt_regs(current)))
total_context_size += riscv_v_sc_size;
}
@@ -284,7 +284,7 @@ static long setup_sigcontext(struct rt_sigframe __user *frame,
if (has_fpu())
err |= save_fp_state(regs, &sc->sc_fpregs);
/* Save the vector state. */
- if (has_vector() && riscv_v_vstate_query(regs))
+ if ((has_vector() || has_xtheadvector()) && riscv_v_vstate_query(regs))
err |= save_v_state(regs, (void __user **)&sc_ext_ptr);
/* Write zero to fp-reserved space and check it on restore_sigcontext */
err |= __put_user(0, &sc->sc_extdesc.reserved);
diff --git a/arch/riscv/kernel/vector.c b/arch/riscv/kernel/vector.c
index 3ba2f2432483..83126995f61a 100644
--- a/arch/riscv/kernel/vector.c
+++ b/arch/riscv/kernel/vector.c
@@ -63,7 +63,7 @@ int riscv_v_setup_vsize(void)

void __init riscv_v_setup_ctx_cache(void)
{
- if (!has_vector())
+ if (!(has_vector() || has_xtheadvector()))
return;

riscv_v_user_cachep = kmem_cache_create_usercopy("riscv_vector_ctx",
@@ -184,7 +184,8 @@ bool riscv_v_first_use_handler(struct pt_regs *regs)
u32 insn = (u32)regs->badaddr;

/* Do not handle if V is not supported, or disabled */
- if (!(ELF_HWCAP & COMPAT_HWCAP_ISA_V))
+ if (!(ELF_HWCAP & COMPAT_HWCAP_ISA_V) &&
+ !(has_xtheadvector() && riscv_v_vstate_ctrl_user_allowed()))
return false;

/* If V has been enabled then it is not the first-use trap */
@@ -223,7 +224,7 @@ void riscv_v_vstate_ctrl_init(struct task_struct *tsk)
bool inherit;
int cur, next;

- if (!has_vector())
+ if (!(has_vector() || has_xtheadvector()))
return;

next = riscv_v_ctrl_get_next(tsk);
@@ -245,7 +246,7 @@ void riscv_v_vstate_ctrl_init(struct task_struct *tsk)

long riscv_v_vstate_ctrl_get_current(void)
{
- if (!has_vector())
+ if (!(has_vector() || has_xtheadvector()))
return -EINVAL;

return current->thread.vstate_ctrl & PR_RISCV_V_VSTATE_CTRL_MASK;
@@ -256,7 +257,7 @@ long riscv_v_vstate_ctrl_set_current(unsigned long arg)
bool inherit;
int cur, next;

- if (!has_vector())
+ if (!(has_vector() || has_xtheadvector()))
return -EINVAL;

if (arg & ~PR_RISCV_V_VSTATE_CTRL_MASK)
@@ -306,7 +307,7 @@ static struct ctl_table riscv_v_default_vstate_table[] = {

static int __init riscv_v_sysctl_init(void)
{
- if (has_vector())
+ if (has_vector() || has_xtheadvector())
if (!register_sysctl("abi", riscv_v_default_vstate_table))
return -EINVAL;
return 0;