[PATCH 0/3] RISC-V KVM preparation

[PATCH 0/3] RISC-V KVM preparation

[Anup Patel]

This patch series is factored-out from the KVM RISC-V v11 series and is
based upon Linux-5.7-rc2.

These patches are mostly preparatory changes in Linux RISC-V kernel which
we require for KVM RISC-V implementation. Also, most of these patches are
already reviewed as part of original KVM RISC-V series.

Anup Patel (3):
  RISC-V: Export riscv_cpuid_to_hartid_mask() API
  RISC-V: Add bitmap reprensenting ISA features common across CPUs
  RISC-V: Remove N-extension related defines

 arch/riscv/include/asm/csr.h   |  3 --
 arch/riscv/include/asm/hwcap.h | 22 +++++++++
 arch/riscv/kernel/cpufeature.c | 83 ++++++++++++++++++++++++++++++++--
 arch/riscv/kernel/smp.c        |  2 +
 4 files changed, 104 insertions(+), 6 deletions(-)

-- 
2.25.1

[PATCH 1/3] RISC-V: Export riscv_cpuid_to_hartid_mask() API

[Anup Patel]

The riscv_cpuid_to_hartid_mask() API should be exported to allow
building KVM RISC-V as loadable module.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com>
---
 arch/riscv/kernel/smp.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
index e0a6293093f1..a65a8fa0c22d 100644
--- a/arch/riscv/kernel/smp.c
+++ b/arch/riscv/kernel/smp.c
@@ -10,6 +10,7 @@
 
 #include <linux/cpu.h>
 #include <linux/interrupt.h>
+#include <linux/module.h>
 #include <linux/profile.h>
 #include <linux/smp.h>
 #include <linux/sched.h>
@@ -63,6 +64,7 @@ void riscv_cpuid_to_hartid_mask(const struct cpumask *in, struct cpumask *out)
 	for_each_cpu(cpu, in)
 		cpumask_set_cpu(cpuid_to_hartid_map(cpu), out);
 }
+EXPORT_SYMBOL_GPL(riscv_cpuid_to_hartid_mask);
 
 bool arch_match_cpu_phys_id(int cpu, u64 phys_id)
 {
-- 
2.25.1

[PATCH 2/3] RISC-V: Add bitmap reprensenting ISA features common across CPUs

[Anup Patel]

This patch adds riscv_isa bitmap which represents Host ISA features
common across all Host 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 for riscv_isa bitmap is in KVM hypervisor where
we will use it 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>
Reviewed-by: Alexander Graf <graf@amazon.com>
---
 arch/riscv/include/asm/hwcap.h | 22 +++++++++
 arch/riscv/kernel/cpufeature.c | 83 ++++++++++++++++++++++++++++++++--
 2 files changed, 102 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
index 1bb0cd04aec3..5ce50468aff1 100644
--- a/arch/riscv/include/asm/hwcap.h
+++ b/arch/riscv/include/asm/hwcap.h
@@ -8,6 +8,7 @@
 #ifndef _ASM_RISCV_HWCAP_H
 #define _ASM_RISCV_HWCAP_H
 
+#include <linux/bits.h>
 #include <uapi/asm/hwcap.h>
 
 #ifndef __ASSEMBLY__
@@ -22,6 +23,27 @@ enum {
 };
 
 extern unsigned long elf_hwcap;
+
+#define RISCV_ISA_EXT_a		('a' - 'a')
+#define RISCV_ISA_EXT_c		('c' - 'a')
+#define RISCV_ISA_EXT_d		('d' - 'a')
+#define RISCV_ISA_EXT_f		('f' - 'a')
+#define RISCV_ISA_EXT_h		('h' - 'a')
+#define RISCV_ISA_EXT_i		('i' - 'a')
+#define RISCV_ISA_EXT_m		('m' - 'a')
+#define RISCV_ISA_EXT_s		('s' - 'a')
+#define RISCV_ISA_EXT_u		('u' - 'a')
+
+#define RISCV_ISA_EXT_MAX	64
+
+unsigned long riscv_isa_extension_base(const unsigned long *isa_bitmap);
+
+#define riscv_isa_extension_mask(ext) BIT_MASK(RISCV_ISA_EXT_##ext)
+
+bool __riscv_isa_extension_available(const unsigned long *isa_bitmap, int bit);
+#define riscv_isa_extension_available(isa_bitmap, ext)	\
+	__riscv_isa_extension_available(isa_bitmap, RISCV_ISA_EXT_##ext)
+
 #endif
 
 #endif /* _ASM_RISCV_HWCAP_H */
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index a5ad00043104..ac202f44a670 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -6,6 +6,7 @@
  * Copyright (C) 2017 SiFive
  */
 
+#include <linux/bitmap.h>
 #include <linux/of.h>
 #include <asm/processor.h>
 #include <asm/hwcap.h>
@@ -13,15 +14,57 @@
 #include <asm/switch_to.h>
 
 unsigned long elf_hwcap __read_mostly;
+
+/* Host ISA bitmap */
+static DECLARE_BITMAP(riscv_isa, RISCV_ISA_EXT_MAX) __read_mostly;
+
 #ifdef CONFIG_FPU
 bool has_fpu __read_mostly;
 #endif
 
+/**
+ * riscv_isa_extension_base() - Get base extension word
+ *
+ * @isa_bitmap: ISA bitmap to use
+ * Return: base extension word as unsigned long value
+ *
+ * NOTE: If isa_bitmap is NULL then Host ISA bitmap will be used.
+ */
+unsigned long riscv_isa_extension_base(const unsigned long *isa_bitmap)
+{
+	if (!isa_bitmap)
+		return riscv_isa[0];
+	return isa_bitmap[0];
+}
+EXPORT_SYMBOL_GPL(riscv_isa_extension_base);
+
+/**
+ * __riscv_isa_extension_available() - Check whether given extension
+ * is available or not
+ *
+ * @isa_bitmap: ISA bitmap to use
+ * @bit: bit position of the desired extension
+ * Return: true or false
+ *
+ * NOTE: If isa_bitmap is NULL then Host ISA bitmap will be used.
+ */
+bool __riscv_isa_extension_available(const unsigned long *isa_bitmap, int bit)
+{
+	const unsigned long *bmap = (isa_bitmap) ? isa_bitmap : riscv_isa;
+
+	if (bit >= RISCV_ISA_EXT_MAX)
+		return false;
+
+	return test_bit(bit, bmap) ? true : false;
+}
+EXPORT_SYMBOL_GPL(__riscv_isa_extension_available);
+
 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;
@@ -33,8 +76,11 @@ void riscv_fill_hwcap(void)
 
 	elf_hwcap = 0;
 
+	bitmap_zero(riscv_isa, RISCV_ISA_EXT_MAX);
+
 	for_each_of_cpu_node(node) {
 		unsigned long this_hwcap = 0;
+		unsigned long this_isa = 0;
 
 		if (riscv_of_processor_hartid(node) < 0)
 			continue;
@@ -44,8 +90,24 @@ void riscv_fill_hwcap(void)
 			continue;
 		}
 
-		for (i = 0; i < strlen(isa); ++i)
+		i = 0;
+		isa_len = strlen(isa);
+#if IS_ENABLED(CONFIG_32BIT)
+		if (!strncmp(isa, "rv32", 4))
+			i += 4;
+#elif IS_ENABLED(CONFIG_64BIT)
+		if (!strncmp(isa, "rv64", 4))
+			i += 4;
+#endif
+		for (; i < isa_len; ++i) {
 			this_hwcap |= isa2hwcap[(unsigned char)(isa[i])];
+			/*
+			 * TODO: X, Y and Z extension parsing for Host ISA
+			 * bitmap will be added in-future.
+			 */
+			if ('a' <= isa[i] && isa[i] < 'x')
+				this_isa |= (1UL << (isa[i] - 'a'));
+		}
 
 		/*
 		 * All "okay" hart should have same isa. Set HWCAP based on
@@ -56,6 +118,11 @@ void riscv_fill_hwcap(void)
 			elf_hwcap &= this_hwcap;
 		else
 			elf_hwcap = this_hwcap;
+
+		if (riscv_isa[0])
+			riscv_isa[0] &= this_isa;
+		else
+			riscv_isa[0] = this_isa;
 	}
 
 	/* We don't support systems with F but without D, so mask those out
@@ -65,7 +132,17 @@ 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[0] & BIT_MASK(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 & BIT_MASK(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))
-- 
2.25.1

[PATCH 3/3] RISC-V: Remove N-extension related defines

[Anup Patel]

The RISC-V N-extension is still in draft state hence remove
N-extension related defines from asm/csr.h.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
---
 arch/riscv/include/asm/csr.h | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
index 8e18d2c64399..cec462e198ce 100644
--- a/arch/riscv/include/asm/csr.h
+++ b/arch/riscv/include/asm/csr.h
@@ -51,13 +51,10 @@
 #define CAUSE_IRQ_FLAG		(_AC(1, UL) << (__riscv_xlen - 1))
 
 /* Interrupt causes (minus the high bit) */
-#define IRQ_U_SOFT		0
 #define IRQ_S_SOFT		1
 #define IRQ_M_SOFT		3
-#define IRQ_U_TIMER		4
 #define IRQ_S_TIMER		5
 #define IRQ_M_TIMER		7
-#define IRQ_U_EXT		8
 #define IRQ_S_EXT		9
 #define IRQ_M_EXT		11
 
-- 
2.25.1

Re: [PATCH 0/3] RISC-V KVM preparation

[Palmer Dabbelt]

On Thu, 23 Apr 2020 21:59:25 PDT (-0700), Anup Patel wrote:
> This patch series is factored-out from the KVM RISC-V v11 series and is
> based upon Linux-5.7-rc2.
>
> These patches are mostly preparatory changes in Linux RISC-V kernel which
> we require for KVM RISC-V implementation. Also, most of these patches are
> already reviewed as part of original KVM RISC-V series.
>
> Anup Patel (3):
>   RISC-V: Export riscv_cpuid_to_hartid_mask() API
>   RISC-V: Add bitmap reprensenting ISA features common across CPUs
>   RISC-V: Remove N-extension related defines
>
>  arch/riscv/include/asm/csr.h   |  3 --
>  arch/riscv/include/asm/hwcap.h | 22 +++++++++
>  arch/riscv/kernel/cpufeature.c | 83 ++++++++++++++++++++++++++++++++--
>  arch/riscv/kernel/smp.c        |  2 +
>  4 files changed, 104 insertions(+), 6 deletions(-)

These are on fixes.