lkml.org 
[lkml]   [2019]   [Aug]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v4 2/4] RISC-V: Add riscv_isa reprensenting ISA features common across CPUs
Date
From: Anup Patel <anup.patel@wdc.com>

This patch adds riscv_isa integer to represent ISA features common
across all CPUs. The riscv_isa is not same as elf_hwcap because
elf_hwcap will only have ISA features relevant for user-space apps
whereas riscv_isa will have ISA features relevant to both kernel
and user-space apps.

One of the use case is KVM hypervisor where riscv_isa will be used
to do following operations:

1. Check whether hypervisor extension is available
2. Find ISA features that need to be virtualized (e.g. floating
point support, vector extension, etc.)

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Signed-off-by: Atish Patra <atish.patra@wdc.com>
---
arch/riscv/include/asm/hwcap.h | 16 ++++++++++++++
arch/riscv/kernel/cpufeature.c | 39 +++++++++++++++++++++++++++++++---
2 files changed, 52 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
index 7ecb7c6a57b1..717306780add 100644
--- a/arch/riscv/include/asm/hwcap.h
+++ b/arch/riscv/include/asm/hwcap.h
@@ -22,5 +22,21 @@ enum {
};

extern unsigned long elf_hwcap;
+
+#define RISCV_ISA_EXT_a (1UL << ('a' - 'a'))
+#define RISCV_ISA_EXT_c (1UL << ('c' - 'a'))
+#define RISCV_ISA_EXT_d (1UL << ('d' - 'a'))
+#define RISCV_ISA_EXT_f (1UL << ('f' - 'a'))
+#define RISCV_ISA_EXT_h (1UL << ('h' - 'a'))
+#define RISCV_ISA_EXT_i (1UL << ('i' - 'a'))
+#define RISCV_ISA_EXT_m (1UL << ('m' - 'a'))
+#define RISCV_ISA_EXT_s (1UL << ('s' - 'a'))
+#define RISCV_ISA_EXT_u (1UL << ('u' - 'a'))
+
+extern unsigned long riscv_isa;
+
+#define riscv_isa_extension_available(ext_char) \
+ (riscv_isa & RISCV_ISA_EXT_##ext_char)
+
#endif
#endif
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index b1ade9a49347..becc99272341 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -12,6 +12,9 @@
#include <asm/smp.h>

unsigned long elf_hwcap __read_mostly;
+unsigned long riscv_isa __read_mostly;
+EXPORT_SYMBOL_GPL(riscv_isa);
+
#ifdef CONFIG_FPU
bool has_fpu __read_mostly;
#endif
@@ -20,7 +23,8 @@ void riscv_fill_hwcap(void)
{
struct device_node *node;
const char *isa;
- size_t i;
+ char print_str[BITS_PER_LONG+1];
+ size_t i, j, isa_len;
static unsigned long isa2hwcap[256] = {0};

isa2hwcap['i'] = isa2hwcap['I'] = COMPAT_HWCAP_ISA_I;
@@ -31,9 +35,11 @@ void riscv_fill_hwcap(void)
isa2hwcap['c'] = isa2hwcap['C'] = COMPAT_HWCAP_ISA_C;

elf_hwcap = 0;
+ riscv_isa = 0;

for_each_of_cpu_node(node) {
unsigned long this_hwcap = 0;
+ unsigned long this_isa = 0;

if (riscv_of_processor_hartid(node) < 0)
continue;
@@ -43,8 +49,20 @@ void riscv_fill_hwcap(void)
continue;
}

- for (i = 0; i < strlen(isa); ++i)
+ i = 0;
+ isa_len = strlen(isa);
+#if defined(CONFIG_32BIT)
+ if (!strncmp(isa, "rv32", 4))
+ i += 4;
+#elif defined(CONFIG_64BIT)
+ if (!strncmp(isa, "rv64", 4))
+ i += 4;
+#endif
+ for (; i < isa_len; ++i) {
this_hwcap |= isa2hwcap[(unsigned char)(isa[i])];
+ if ('a' <= isa[i] && isa[i] <= 'z')
+ this_isa |= (1UL << (isa[i] - 'a'));
+ }

/*
* All "okay" hart should have same isa. Set HWCAP based on
@@ -55,6 +73,11 @@ void riscv_fill_hwcap(void)
elf_hwcap &= this_hwcap;
else
elf_hwcap = this_hwcap;
+
+ if (riscv_isa)
+ riscv_isa &= this_isa;
+ else
+ riscv_isa = this_isa;
}

/* We don't support systems with F but without D, so mask those out
@@ -64,7 +87,17 @@ void riscv_fill_hwcap(void)
elf_hwcap &= ~COMPAT_HWCAP_ISA_F;
}

- pr_info("elf_hwcap is 0x%lx\n", elf_hwcap);
+ memset(print_str, 0, sizeof(print_str));
+ for (i = 0, j = 0; i < BITS_PER_LONG; i++)
+ if (riscv_isa & (1UL << i))
+ print_str[j++] = (char)('a' + i);
+ pr_info("riscv: ISA extensions %s\n", print_str);
+
+ memset(print_str, 0, sizeof(print_str));
+ for (i = 0, j = 0; i < BITS_PER_LONG; i++)
+ if (elf_hwcap & (1UL << i))
+ print_str[j++] = (char)('a' + i);
+ pr_info("riscv: ELF capabilities %s\n", print_str);

#ifdef CONFIG_FPU
if (elf_hwcap & (COMPAT_HWCAP_ISA_F | COMPAT_HWCAP_ISA_D))
--
2.21.0
\
 
 \ /
  Last update: 2019-08-03 06:43    [W:0.093 / U:11.940 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site