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From:   Anup Patel <Anup.Patel@wdc.com>
To:     Palmer Dabbelt <palmer@dabbelt.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Radim K <rkrcmar@redhat.com>
CC:     Alexander Graf <graf@amazon.com>,
        Atish Patra <Atish.Patra@wdc.com>,
        Alistair Francis <Alistair.Francis@wdc.com>,
        Damien Le Moal <Damien.LeMoal@wdc.com>,
        Christoph Hellwig <hch@lst.de>,
        Anup Patel <anup@brainfault.org>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        "kvm-riscv@lists.infradead.org" <kvm-riscv@lists.infradead.org>,
        "linux-riscv@lists.infradead.org" <linux-riscv@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Anup Patel <Anup.Patel@wdc.com>
Subject: [PATCH v10 02/19] RISC-V: Add bitmap reprensenting ISA features
 common across CPUs
Thread-Topic: [PATCH v10 02/19] RISC-V: Add bitmap reprensenting ISA features
 common across CPUs
Thread-Index: AQHVuYUS5IbGQwTUD021jPt6po1ITw==
Date:   Mon, 23 Dec 2019 11:35:26 +0000
Message-ID: <20191223113443.68969-3-anup.patel@wdc.com>
References: <20191223113443.68969-1-anup.patel@wdc.com>
In-Reply-To: <20191223113443.68969-1-anup.patel@wdc.com>
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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..5589c012e004 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
=20
+#include <linux/bits.h>
 #include <uapi/asm/hwcap.h>
=20
 #ifndef __ASSEMBLY__
@@ -22,6 +23,27 @@ enum {
 };
=20
 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	256
+
+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
=20
 #endif /* _ASM_RISCV_HWCAP_H */
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.=
c
index 0b40705567b7..e172a2322b34 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -6,6 +6,7 @@
  * Copyright (C) 2017 SiFive
  */
=20
+#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>
=20
 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
=20
+/**
+ * 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 =3D (isa_bitmap) ? isa_bitmap : riscv_isa;
+
+	if (bit >=3D 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] =3D {0};
=20
 	isa2hwcap['i'] =3D isa2hwcap['I'] =3D COMPAT_HWCAP_ISA_I;
@@ -33,8 +76,11 @@ void riscv_fill_hwcap(void)
=20
 	elf_hwcap =3D 0;
=20
+	bitmap_zero(riscv_isa, RISCV_ISA_EXT_MAX);
+
 	for_each_of_cpu_node(node) {
 		unsigned long this_hwcap =3D 0;
+		unsigned long this_isa =3D 0;
=20
 		if (riscv_of_processor_hartid(node) < 0)
 			continue;
@@ -42,8 +88,24 @@ void riscv_fill_hwcap(void)
 		if (riscv_read_check_isa(node, &isa) < 0)
 			continue;
=20
-		for (i =3D 0; i < strlen(isa); ++i)
+		i =3D 0;
+		isa_len =3D strlen(isa);
+#if IS_ENABLED(CONFIG_32BIT)
+		if (!strncmp(isa, "rv32", 4))
+			i +=3D 4;
+#elif IS_ENABLED(CONFIG_64BIT)
+		if (!strncmp(isa, "rv64", 4))
+			i +=3D 4;
+#endif
+		for (; i < isa_len; ++i) {
 			this_hwcap |=3D isa2hwcap[(unsigned char)(isa[i])];
+			/*
+			 * TODO: X, Y and Z extension parsing for Host ISA
+			 * bitmap will be added in-future.
+			 */
+			if ('a' <=3D isa[i] && isa[i] < 'x')
+				this_isa |=3D (1UL << (isa[i] - 'a'));
+		}
=20
 		/*
 		 * All "okay" hart should have same isa. Set HWCAP based on
@@ -54,6 +116,11 @@ void riscv_fill_hwcap(void)
 			elf_hwcap &=3D this_hwcap;
 		else
 			elf_hwcap =3D this_hwcap;
+
+		if (riscv_isa[0])
+			riscv_isa[0] &=3D this_isa;
+		else
+			riscv_isa[0] =3D this_isa;
 	}
=20
 	/* We don't support systems with F but without D, so mask those out
@@ -63,7 +130,17 @@ void riscv_fill_hwcap(void)
 		elf_hwcap &=3D ~COMPAT_HWCAP_ISA_F;
 	}
=20
-	pr_info("elf_hwcap is 0x%lx\n", elf_hwcap);
+	memset(print_str, 0, sizeof(print_str));
+	for (i =3D 0, j =3D 0; i < BITS_PER_LONG; i++)
+		if (riscv_isa[0] & BIT_MASK(i))
+			print_str[j++] =3D (char)('a' + i);
+	pr_info("riscv: ISA extensions %s\n", print_str);
+
+	memset(print_str, 0, sizeof(print_str));
+	for (i =3D 0, j =3D 0; i < BITS_PER_LONG; i++)
+		if (elf_hwcap & BIT_MASK(i))
+			print_str[j++] =3D (char)('a' + i);
+	pr_info("riscv: ELF capabilities %s\n", print_str);
=20
 #ifdef CONFIG_FPU
 	if (elf_hwcap & (COMPAT_HWCAP_ISA_F | COMPAT_HWCAP_ISA_D))
--=20
2.17.1