[PATCH 13/19] riscv: vector: Support xtheadvector save/restore

From: Charlie Jenkins
Date: Fri Apr 12 2024 - 00:14:58 EST

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

Signed-off-by: Charlie Jenkins <charlie@xxxxxxxxxxxx>
---
arch/riscv/include/asm/csr.h | 6 +
arch/riscv/include/asm/vector.h | 228 +++++++++++++++++++++++++--------
arch/riscv/kernel/kernel_mode_vector.c | 4 +-
arch/riscv/kernel/vector.c | 22 +++-
4 files changed, 203 insertions(+), 57 deletions(-)

diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
index e5a35efd56e0..13657d096e7d 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/vector.h b/arch/riscv/include/asm/vector.h
index 731dcd0ed4de..f6ca30dd7d86 100644
--- a/arch/riscv/include/asm/vector.h
+++ b/arch/riscv/include/asm/vector.h
@@ -18,6 +18,25 @@
#include <asm/cpufeature.h>
#include <asm/csr.h>
#include <asm/asm.h>
+#include <asm/xtheadvector.h>
+
+#define __riscv_v_vstate_or(_val, TYPE) ({ \
+ typeof(_val) _res = _val; \
+ if (riscv_has_vendor_extension_unlikely(RISCV_ISA_VENDOR_EXT_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 (riscv_has_vendor_extension_unlikely(RISCV_ISA_VENDOR_EXT_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);
@@ -42,37 +61,43 @@ static __always_inline bool has_vector(void)

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 (riscv_has_vendor_extension_unlikely(RISCV_ISA_VENDOR_EXT_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 (riscv_has_vendor_extension_unlikely(RISCV_ISA_VENDOR_EXT_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 +106,47 @@ 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 (riscv_has_vendor_extension_unlikely(RISCV_ISA_VENDOR_EXT_XTHEADVECTOR)) {
+ u32 tmp_vcsr;
+ bool restore_fpu = false;
+ unsigned long status = csr_read(CSR_SSTATUS);
+
+ /*
+ * 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.
+ */
+ if ((status & SR_FS) == SR_FS_OFF) {
+ csr_set(CSR_SSTATUS, (status & ~SR_FS) | SR_FS_CLEAN);
+ restore_fpu = true;
+ }
+
+ asm volatile (
+ "csrr %[tmp_vcsr], " __stringify(VCSR_VXRM) "\n\t"
+ "slliw %[vcsr], %[tmp_vcsr], " __stringify(VCSR_VXRM_SHIFT) "\n\t"
+ "csrr %[tmp_vcsr], " __stringify(VCSR_VXSAT) "\n\t"
+ "or %[vcsr], %[vcsr], %[tmp_vcsr]\n\t"
+ : [vcsr] "=r" (dest->vcsr), [tmp_vcsr] "=&r" (tmp_vcsr));
+
+ if (restore_fpu)
+ csr_set(CSR_SSTATUS, status);
+ } else {
+ asm volatile (
+ "csrr %[vcsr], " __stringify(CSR_VCSR) "\n\t"
+ "csrr %[vlenb], " __stringify(CSR_VLENB) "\n\t"
+ : [vcsr] "=r" (dest->vcsr), [vlenb] "=r" (dest->vlenb));
+ }
}

static __always_inline void __vstate_csr_restore(struct __riscv_v_ext_state *src)
@@ -95,9 +157,37 @@ 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 (riscv_has_vendor_extension_unlikely(RISCV_ISA_VENDOR_EXT_XTHEADVECTOR)) {
+ u32 tmp_vcsr;
+ bool restore_fpu = false;
+ 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.
+ */
+ if ((status & SR_FS) == SR_FS_OFF) {
+ csr_set(CSR_SSTATUS, (status & ~SR_FS) | SR_FS_CLEAN);
+ restore_fpu = true;
+ }
+
+ asm volatile (
+ "srliw %[tmp_vcsr], %[vcsr], " __stringify(VCSR_VXRM_SHIFT) "\n\t"
+ "andi %[tmp_vcsr], %[tmp_vcsr], " __stringify(VCSR_VXRM_MASK) "\n\t"
+ "csrw " __stringify(VCSR_VXRM) ", %[tmp_vcsr]\n\t"
+ "andi %[tmp_vcsr], %[vcsr], " __stringify(VCSR_VXSAT_MASK) "\n\t"
+ "csrw " __stringify(VCSR_VXSAT) ", %[tmp_vcsr]\n\t"
+ : [tmp_vcsr] "=&r" (tmp_vcsr) : [vcsr] "r" (src->vcsr));
+
+ if (restore_fpu)
+ csr_set(CSR_SSTATUS, status);
+ } else {
+ asm volatile (
+ "csrw " __stringify(CSR_VCSR) ", %[vcsr]\n\t"
+ : : [vcsr] "r" (src->vcsr));
+ }
}

static inline void __riscv_v_vstate_save(struct __riscv_v_ext_state *save_to,
@@ -107,19 +197,33 @@ 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 (riscv_has_vendor_extension_unlikely(RISCV_ISA_VENDOR_EXT_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 +233,77 @@ 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 (riscv_has_vendor_extension_unlikely(RISCV_ISA_VENDOR_EXT_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 (riscv_has_vendor_extension_unlikely(RISCV_ISA_VENDOR_EXT_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 +312,7 @@ 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 +321,7 @@ 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/kernel_mode_vector.c b/arch/riscv/kernel/kernel_mode_vector.c
index 6afe80c7f03a..ad70fc581dbe 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();
diff --git a/arch/riscv/kernel/vector.c b/arch/riscv/kernel/vector.c
index 6727d1d3b8f2..d8ec2757cc2e 100644
--- a/arch/riscv/kernel/vector.c
+++ b/arch/riscv/kernel/vector.c
@@ -33,10 +33,24 @@ int riscv_v_setup_vsize(void)
{
unsigned long this_vsize;

- /* There are 32 vector registers with vlenb length. */
- riscv_v_enable();
- this_vsize = csr_read(CSR_VLENB) * 32;
- riscv_v_disable();
+ /*
+ * This is called before alternatives have been patched so can't use
+ * riscv_has_vendor_extension_unlikely
+ */
+ if (__riscv_isa_vendor_extension_available(NULL, RISCV_ISA_VENDOR_EXT_XTHEADVECTOR)) {
+ /*
+ * Although xtheadvector states that th.vlenb exists and
+ * overlaps with the vector 1.0 extension overlaps, an illegal
+ * instruction is raised if read. These systems all currently
+ * have a fixed vector length of 128, so hardcode that value.
+ */
+ this_vsize = 128;
+ } else {
+ /* There are 32 vector registers with vlenb length. */
+ riscv_v_enable();
+ this_vsize = csr_read(CSR_VLENB) * 32;
+ riscv_v_disable();
+ }

if (!riscv_v_vsize) {
riscv_v_vsize = this_vsize;

--
2.44.0

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