[PATCH v7 20/27] arm64/sve: In-kernel vector length availability query interface

Dave Martin
2019-03-29T13:31:39Z

KVM will need to interrogate the set of SVE vector lengths
available on the system.

This patch exposes the relevant bits to the kernel, along with a
sve_vq_available() helper to check whether a particular vector
length is supported.

__vq_to_bit() and __bit_to_vq() are not intended for use outside
these functions: now that these are exposed outside fpsimd.c, they
are prefixed with __ in order to provide an extra hint that they
are not intended for general-purpose use.

Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: zhang.lei <zhang.lei@jp.fujitsu.com>
---
arch/arm64/include/asm/fpsimd.h | 29 +++++++++++++++++++++++++++++
arch/arm64/kernel/fpsimd.c | 35 ++++++++---------------------------
2 files changed, 37 insertions(+), 27 deletions(-)

diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h
index df7a143..ad6d2e4 100644
--- a/arch/arm64/include/asm/fpsimd.h
+++ b/arch/arm64/include/asm/fpsimd.h
@@ -24,10 +24,13 @@

#ifndef __ASSEMBLY__

+#include <linux/bitmap.h>
#include <linux/build_bug.h>
+#include <linux/bug.h>
#include <linux/cache.h>
#include <linux/init.h>
#include <linux/stddef.h>
+#include <linux/types.h>

#if defined(__KERNEL__) && defined(CONFIG_COMPAT)
/* Masks for extracting the FPSR and FPCR from the FPSCR */
@@ -89,6 +92,32 @@ extern u64 read_zcr_features(void);

extern int __ro_after_init sve_max_vl;
extern int __ro_after_init sve_max_virtualisable_vl;
+/* Set of available vector lengths, as vq_to_bit(vq): */
+extern __ro_after_init DECLARE_BITMAP(sve_vq_map, SVE_VQ_MAX);
+
+/*
+ * Helpers to translate bit indices in sve_vq_map to VQ values (and
+ * vice versa). This allows find_next_bit() to be used to find the
+ * _maximum_ VQ not exceeding a certain value.
+ */
+static inline unsigned int __vq_to_bit(unsigned int vq)
+{
+ return SVE_VQ_MAX - vq;
+}
+
+static inline unsigned int __bit_to_vq(unsigned int bit)
+{
+ if (WARN_ON(bit >= SVE_VQ_MAX))
+ bit = SVE_VQ_MAX - 1;
+
+ return SVE_VQ_MAX - bit;
+}
+
+/* Ensure vq >= SVE_VQ_MIN && vq <= SVE_VQ_MAX before calling this function */
+static inline bool sve_vq_available(unsigned int vq)
+{
+ return test_bit(__vq_to_bit(vq), sve_vq_map);
+}

#ifdef CONFIG_ARM64_SVE

diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 8a93afa..577296b 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -136,7 +136,7 @@ static int sve_default_vl = -1;
int __ro_after_init sve_max_vl = SVE_VL_MIN;
int __ro_after_init sve_max_virtualisable_vl = SVE_VL_MIN;
/* Set of available vector lengths, as vq_to_bit(vq): */
-static __ro_after_init DECLARE_BITMAP(sve_vq_map, SVE_VQ_MAX);
+__ro_after_init DECLARE_BITMAP(sve_vq_map, SVE_VQ_MAX);
/* Set of vector lengths present on at least one cpu: */
static __ro_after_init DECLARE_BITMAP(sve_vq_partial_map, SVE_VQ_MAX);
static void __percpu *efi_sve_state;
@@ -270,25 +270,6 @@ void fpsimd_save(void)
}

/*
- * Helpers to translate bit indices in sve_vq_map to VQ values (and
- * vice versa). This allows find_next_bit() to be used to find the
- * _maximum_ VQ not exceeding a certain value.
- */
-
-static unsigned int vq_to_bit(unsigned int vq)
-{
- return SVE_VQ_MAX - vq;
-}
-
-static unsigned int bit_to_vq(unsigned int bit)
-{
- if (WARN_ON(bit >= SVE_VQ_MAX))
- bit = SVE_VQ_MAX - 1;
-
- return SVE_VQ_MAX - bit;
-}
-
-/*
* All vector length selection from userspace comes through here.
* We're on a slow path, so some sanity-checks are included.
* If things go wrong there's a bug somewhere, but try to fall back to a
@@ -309,8 +290,8 @@ static unsigned int find_supported_vector_length(unsigned int vl)
vl = max_vl;

bit = find_next_bit(sve_vq_map, SVE_VQ_MAX,
- vq_to_bit(sve_vq_from_vl(vl)));
- return sve_vl_from_vq(bit_to_vq(bit));
+ __vq_to_bit(sve_vq_from_vl(vl)));
+ return sve_vl_from_vq(__bit_to_vq(bit));
}

#ifdef CONFIG_SYSCTL
@@ -648,7 +629,7 @@ static void sve_probe_vqs(DECLARE_BITMAP(map, SVE_VQ_MAX))
write_sysreg_s(zcr | (vq - 1), SYS_ZCR_EL1); /* self-syncing */
vl = sve_get_vl();
vq = sve_vq_from_vl(vl); /* skip intervening lengths */
- set_bit(vq_to_bit(vq), map);
+ set_bit(__vq_to_bit(vq), map);
}
}

@@ -717,7 +698,7 @@ int sve_verify_vq_map(void)
* Mismatches above sve_max_virtualisable_vl are fine, since
* no guest is allowed to configure ZCR_EL2.LEN to exceed this:
*/
- if (sve_vl_from_vq(bit_to_vq(b)) <= sve_max_virtualisable_vl) {
+ if (sve_vl_from_vq(__bit_to_vq(b)) <= sve_max_virtualisable_vl) {
pr_warn("SVE: cpu%d: Unsupported vector length(s) present\n",
smp_processor_id());
return -EINVAL;
@@ -801,8 +782,8 @@ void __init sve_setup(void)
* so sve_vq_map must have at least SVE_VQ_MIN set.
* If something went wrong, at least try to patch it up:
*/
- if (WARN_ON(!test_bit(vq_to_bit(SVE_VQ_MIN), sve_vq_map)))
- set_bit(vq_to_bit(SVE_VQ_MIN), sve_vq_map);
+ if (WARN_ON(!test_bit(__vq_to_bit(SVE_VQ_MIN), sve_vq_map)))
+ set_bit(__vq_to_bit(SVE_VQ_MIN), sve_vq_map);

zcr = read_sanitised_ftr_reg(SYS_ZCR_EL1);
sve_max_vl = sve_vl_from_vq((zcr & ZCR_ELx_LEN_MASK) + 1);
@@ -831,7 +812,7 @@ void __init sve_setup(void)
/* No virtualisable VLs? This is architecturally forbidden. */
sve_max_virtualisable_vl = SVE_VQ_MIN;
else /* b + 1 < SVE_VQ_MAX */
- sve_max_virtualisable_vl = sve_vl_from_vq(bit_to_vq(b + 1));
+ sve_max_virtualisable_vl = sve_vl_from_vq(__bit_to_vq(b + 1));

if (sve_max_virtualisable_vl > sve_max_vl)
sve_max_virtualisable_vl = sve_max_vl;
--
2.1.4