diff mbox series

[v3,7/7] RISC-V: Add hwprobe vDSO function and data

Message ID 20230221190858.3159617-8-evan@rivosinc.com
State New
Headers
Series RISC-V Hardware Probing User Interface |

Commit Message

Evan Green Feb. 21, 2023, 7:08 p.m. UTC 
  Add a vDSO function __vdso_riscv_hwprobe, which can sit in front of the
riscv_hwprobe syscall and answer common queries. We stash a copy of
static answers for the "all CPUs" case in the vDSO data page. This data
is private to the vDSO, so we can decide later to change what's stored
there or under what conditions we defer to the syscall. Currently all
data can be discovered at boot, so the vDSO function answers all queries
when the cpumask is set to the "all CPUs" hint.

There's also a boolean in the data that lets the vDSO function know that
all CPUs are the same. In that case, the vDSO will also answer queries
for arbitrary CPU masks in addition to the "all CPUs" hint.

Signed-off-by: Evan Green <evan@rivosinc.com>
---

Changes in v3:
 - Introduced vDSO function


One aspect of this that's less than perfect is that there are two copies
of the arch_vdso_data in the data page. This stems from the fact that
vdso_data is arrayed by CS_BASES. Since we're very far away from filling
up the page, and this is not ABI, I left it for now. If things get full
we can move this data out to its own page, or refactor vdso_data
tree-wide to allow for non-arrayed data.

---
 arch/riscv/Kconfig                   |  1 +
 arch/riscv/include/asm/vdso/data.h   | 17 ++++++++++
 arch/riscv/kernel/sys_riscv.c        | 41 ++++++++++++++++++++++++
 arch/riscv/kernel/vdso/Makefile      |  2 ++
 arch/riscv/kernel/vdso/hwprobe.c     | 47 ++++++++++++++++++++++++++++
 arch/riscv/kernel/vdso/sys_hwprobe.S | 15 +++++++++
 arch/riscv/kernel/vdso/vdso.lds.S    |  1 +
 7 files changed, 124 insertions(+)
 create mode 100644 arch/riscv/include/asm/vdso/data.h
 create mode 100644 arch/riscv/kernel/vdso/hwprobe.c
 create mode 100644 arch/riscv/kernel/vdso/sys_hwprobe.S

Comments

kernel test robot Feb. 21, 2023, 9:17 p.m. UTC | #1 
Hi Evan,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on shuah-kselftest/next]
[also build test WARNING on shuah-kselftest/fixes robh/for-next soc/for-next linus/master v6.2]
[cannot apply to next-20230221]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Evan-Green/RISC-V-Move-struct-riscv_cpuinfo-to-new-header/20230222-031210
base:   https://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest.git next
patch link:    https://lore.kernel.org/r/20230221190858.3159617-8-evan%40rivosinc.com
patch subject: [PATCH v3 7/7] RISC-V: Add hwprobe vDSO function and data
config: riscv-allyesconfig (https://download.01.org/0day-ci/archive/20230222/202302220534.zLN2kaHH-lkp@intel.com/config)
compiler: riscv64-linux-gcc (GCC) 12.1.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/3f47f3f920ffcb37a461d04a1ee0e245451c869e
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Evan-Green/RISC-V-Move-struct-riscv_cpuinfo-to-new-header/20230222-031210
        git checkout 3f47f3f920ffcb37a461d04a1ee0e245451c869e
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=riscv olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=riscv prepare

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Link: https://lore.kernel.org/oe-kbuild-all/202302220534.zLN2kaHH-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> arch/riscv/kernel/vdso/hwprobe.c:14:5: warning: no previous prototype for '__vdso_riscv_hwprobe' [-Wmissing-prototypes]
      14 | int __vdso_riscv_hwprobe(struct riscv_hwprobe *pairs, long pair_count,
         |     ^~~~~~~~~~~~~~~~~~~~
--
   scripts/genksyms/parse.y: warning: 9 shift/reduce conflicts [-Wconflicts-sr]
   scripts/genksyms/parse.y: warning: 5 reduce/reduce conflicts [-Wconflicts-rr]
   scripts/genksyms/parse.y: note: rerun with option '-Wcounterexamples' to generate conflict counterexamples
>> arch/riscv/kernel/vdso/hwprobe.c:14:5: warning: no previous prototype for '__vdso_riscv_hwprobe' [-Wmissing-prototypes]
      14 | int __vdso_riscv_hwprobe(struct riscv_hwprobe *pairs, long pair_count,
         |     ^~~~~~~~~~~~~~~~~~~~


vim +/__vdso_riscv_hwprobe +14 arch/riscv/kernel/vdso/hwprobe.c

     9	
    10	extern int riscv_hwprobe(struct riscv_hwprobe *pairs, long pair_count,
    11				 long cpu_count, unsigned long *cpus,
    12				 unsigned long flags);
    13	
  > 14	int __vdso_riscv_hwprobe(struct riscv_hwprobe *pairs, long pair_count,
kernel test robot Feb. 22, 2023, 6:55 a.m. UTC | #2 
Hi Evan,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on shuah-kselftest/next]
[also build test ERROR on shuah-kselftest/fixes robh/for-next soc/for-next linus/master v6.2]
[cannot apply to next-20230222]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Evan-Green/RISC-V-Move-struct-riscv_cpuinfo-to-new-header/20230222-031210
base:   https://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest.git next
patch link:    https://lore.kernel.org/r/20230221190858.3159617-8-evan%40rivosinc.com
patch subject: [PATCH v3 7/7] RISC-V: Add hwprobe vDSO function and data
config: riscv-rv32_defconfig (https://download.01.org/0day-ci/archive/20230222/202302221419.SOkwfXfm-lkp@intel.com/config)
compiler: riscv32-linux-gcc (GCC) 12.1.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/3f47f3f920ffcb37a461d04a1ee0e245451c869e
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Evan-Green/RISC-V-Move-struct-riscv_cpuinfo-to-new-header/20230222-031210
        git checkout 3f47f3f920ffcb37a461d04a1ee0e245451c869e
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=riscv olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=riscv prepare

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Link: https://lore.kernel.org/oe-kbuild-all/202302221419.SOkwfXfm-lkp@intel.com/

All errors (new ones prefixed by >>):

   In file included from include/vdso/datapage.h:137,
                    from arch/riscv/kernel/vdso/hwprobe.c:7:
   arch/riscv/include/asm/vdso/gettimeofday.h: In function 'gettimeofday_fallback':
>> arch/riscv/include/asm/vdso/gettimeofday.h:21:38: error: '__NR_gettimeofday' undeclared (first use in this function)
      21 |         register long nr asm("a7") = __NR_gettimeofday;
         |                                      ^~~~~~~~~~~~~~~~~
   arch/riscv/include/asm/vdso/gettimeofday.h:21:38: note: each undeclared identifier is reported only once for each function it appears in
   arch/riscv/include/asm/vdso/gettimeofday.h: In function 'clock_gettime_fallback':
>> arch/riscv/include/asm/vdso/gettimeofday.h:37:38: error: '__NR_clock_gettime' undeclared (first use in this function)
      37 |         register long nr asm("a7") = __NR_clock_gettime;
         |                                      ^~~~~~~~~~~~~~~~~~
   arch/riscv/include/asm/vdso/gettimeofday.h: In function 'clock_getres_fallback':
>> arch/riscv/include/asm/vdso/gettimeofday.h:53:38: error: '__NR_clock_getres' undeclared (first use in this function)
      53 |         register long nr asm("a7") = __NR_clock_getres;
         |                                      ^~~~~~~~~~~~~~~~~
   arch/riscv/kernel/vdso/hwprobe.c: At top level:
   arch/riscv/kernel/vdso/hwprobe.c:14:5: warning: no previous prototype for '__vdso_riscv_hwprobe' [-Wmissing-prototypes]
      14 | int __vdso_riscv_hwprobe(struct riscv_hwprobe *pairs, long pair_count,
         |     ^~~~~~~~~~~~~~~~~~~~
   make[2]: *** [scripts/Makefile.build:252: arch/riscv/kernel/vdso/hwprobe.o] Error 1
   make[2]: Target 'include/generated/vdso-offsets.h' not remade because of errors.
   make[1]: *** [arch/riscv/Makefile:126: vdso_prepare] Error 2
   make[1]: Target 'prepare' not remade because of errors.
   make: *** [Makefile:242: __sub-make] Error 2
   make: Target 'prepare' not remade because of errors.


vim +/__NR_gettimeofday +21 arch/riscv/include/asm/vdso/gettimeofday.h

ad5d1122b82fbd6 Vincent Chen 2020-06-09  13  
ad5d1122b82fbd6 Vincent Chen 2020-06-09  14  static __always_inline
ad5d1122b82fbd6 Vincent Chen 2020-06-09  15  int gettimeofday_fallback(struct __kernel_old_timeval *_tv,
ad5d1122b82fbd6 Vincent Chen 2020-06-09  16  			  struct timezone *_tz)
ad5d1122b82fbd6 Vincent Chen 2020-06-09  17  {
ad5d1122b82fbd6 Vincent Chen 2020-06-09  18  	register struct __kernel_old_timeval *tv asm("a0") = _tv;
ad5d1122b82fbd6 Vincent Chen 2020-06-09  19  	register struct timezone *tz asm("a1") = _tz;
ad5d1122b82fbd6 Vincent Chen 2020-06-09  20  	register long ret asm("a0");
ad5d1122b82fbd6 Vincent Chen 2020-06-09 @21  	register long nr asm("a7") = __NR_gettimeofday;
ad5d1122b82fbd6 Vincent Chen 2020-06-09  22  
ad5d1122b82fbd6 Vincent Chen 2020-06-09  23  	asm volatile ("ecall\n"
ad5d1122b82fbd6 Vincent Chen 2020-06-09  24  		      : "=r" (ret)
ad5d1122b82fbd6 Vincent Chen 2020-06-09  25  		      : "r"(tv), "r"(tz), "r"(nr)
ad5d1122b82fbd6 Vincent Chen 2020-06-09  26  		      : "memory");
ad5d1122b82fbd6 Vincent Chen 2020-06-09  27  
ad5d1122b82fbd6 Vincent Chen 2020-06-09  28  	return ret;
ad5d1122b82fbd6 Vincent Chen 2020-06-09  29  }
ad5d1122b82fbd6 Vincent Chen 2020-06-09  30  
ad5d1122b82fbd6 Vincent Chen 2020-06-09  31  static __always_inline
ad5d1122b82fbd6 Vincent Chen 2020-06-09  32  long clock_gettime_fallback(clockid_t _clkid, struct __kernel_timespec *_ts)
ad5d1122b82fbd6 Vincent Chen 2020-06-09  33  {
ad5d1122b82fbd6 Vincent Chen 2020-06-09  34  	register clockid_t clkid asm("a0") = _clkid;
ad5d1122b82fbd6 Vincent Chen 2020-06-09  35  	register struct __kernel_timespec *ts asm("a1") = _ts;
ad5d1122b82fbd6 Vincent Chen 2020-06-09  36  	register long ret asm("a0");
ad5d1122b82fbd6 Vincent Chen 2020-06-09 @37  	register long nr asm("a7") = __NR_clock_gettime;
ad5d1122b82fbd6 Vincent Chen 2020-06-09  38  
ad5d1122b82fbd6 Vincent Chen 2020-06-09  39  	asm volatile ("ecall\n"
ad5d1122b82fbd6 Vincent Chen 2020-06-09  40  		      : "=r" (ret)
ad5d1122b82fbd6 Vincent Chen 2020-06-09  41  		      : "r"(clkid), "r"(ts), "r"(nr)
ad5d1122b82fbd6 Vincent Chen 2020-06-09  42  		      : "memory");
ad5d1122b82fbd6 Vincent Chen 2020-06-09  43  
ad5d1122b82fbd6 Vincent Chen 2020-06-09  44  	return ret;
ad5d1122b82fbd6 Vincent Chen 2020-06-09  45  }
ad5d1122b82fbd6 Vincent Chen 2020-06-09  46  
ad5d1122b82fbd6 Vincent Chen 2020-06-09  47  static __always_inline
ad5d1122b82fbd6 Vincent Chen 2020-06-09  48  int clock_getres_fallback(clockid_t _clkid, struct __kernel_timespec *_ts)
ad5d1122b82fbd6 Vincent Chen 2020-06-09  49  {
ad5d1122b82fbd6 Vincent Chen 2020-06-09  50  	register clockid_t clkid asm("a0") = _clkid;
ad5d1122b82fbd6 Vincent Chen 2020-06-09  51  	register struct __kernel_timespec *ts asm("a1") = _ts;
ad5d1122b82fbd6 Vincent Chen 2020-06-09  52  	register long ret asm("a0");
ad5d1122b82fbd6 Vincent Chen 2020-06-09 @53  	register long nr asm("a7") = __NR_clock_getres;
ad5d1122b82fbd6 Vincent Chen 2020-06-09  54  
ad5d1122b82fbd6 Vincent Chen 2020-06-09  55  	asm volatile ("ecall\n"
ad5d1122b82fbd6 Vincent Chen 2020-06-09  56  		      : "=r" (ret)
ad5d1122b82fbd6 Vincent Chen 2020-06-09  57  		      : "r"(clkid), "r"(ts), "r"(nr)
ad5d1122b82fbd6 Vincent Chen 2020-06-09  58  		      : "memory");
ad5d1122b82fbd6 Vincent Chen 2020-06-09  59  
ad5d1122b82fbd6 Vincent Chen 2020-06-09  60  	return ret;
ad5d1122b82fbd6 Vincent Chen 2020-06-09  61  }
ad5d1122b82fbd6 Vincent Chen 2020-06-09  62
diff mbox series

Patch

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index e2b656043abf..218e75975a15 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -33,6 +33,7 @@  config RISCV
 	select ARCH_HAS_STRICT_MODULE_RWX if MMU && !XIP_KERNEL
 	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
 	select ARCH_HAS_UBSAN_SANITIZE_ALL
+	select ARCH_HAS_VDSO_DATA
 	select ARCH_OPTIONAL_KERNEL_RWX if ARCH_HAS_STRICT_KERNEL_RWX
 	select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 	select ARCH_STACKWALK
diff --git a/arch/riscv/include/asm/vdso/data.h b/arch/riscv/include/asm/vdso/data.h
new file mode 100644
index 000000000000..dc2f76f58b76
--- /dev/null
+++ b/arch/riscv/include/asm/vdso/data.h
@@ -0,0 +1,17 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __RISCV_ASM_VDSO_DATA_H
+#define __RISCV_ASM_VDSO_DATA_H
+
+#include <linux/types.h>
+#include <vdso/datapage.h>
+#include <asm/hwprobe.h>
+
+struct arch_vdso_data {
+	/* Stash static answers to the hwprobe queries when all CPUs are selected. */
+	__u64 all_cpu_hwprobe_values[RISCV_HWPROBE_MAX_KEY + 1];
+
+	/* Boolean indicating all CPUs have the same static hwprobe values. */
+	__u8 homogeneous_cpus;
+};
+
+#endif /* __RISCV_ASM_VDSO_DATA_H */
diff --git a/arch/riscv/kernel/sys_riscv.c b/arch/riscv/kernel/sys_riscv.c
index afc1b96d5c1a..113b3d97c8cc 100644
--- a/arch/riscv/kernel/sys_riscv.c
+++ b/arch/riscv/kernel/sys_riscv.c
@@ -14,6 +14,7 @@ 
 #include <asm/uaccess.h>
 #include <asm/unistd.h>
 #include <asm-generic/mman-common.h>
+#include <vdso/vsyscall.h>
 
 static long riscv_sys_mmap(unsigned long addr, unsigned long len,
 			   unsigned long prot, unsigned long flags,
@@ -242,6 +243,46 @@  int do_riscv_hwprobe(struct riscv_hwprobe __user *pairs, long pair_count,
 
 }
 
+static int __init init_hwprobe_vdso_data(void)
+{
+	struct vdso_data *vd = __arch_get_k_vdso_data();
+	struct arch_vdso_data *avd = &vd->arch_data;
+	u64 id_bitsmash = 0;
+	struct riscv_hwprobe pair;
+	int key;
+
+	/*
+	 * Initialize vDSO data with the answers for the "all CPUs" case, to
+	 * save a syscall in the common case.
+	 */
+	for (key = 0; key <= RISCV_HWPROBE_MAX_KEY; key++) {
+		pair.key = key;
+		hwprobe_one_pair(&pair, cpu_online_mask);
+
+		WARN_ON_ONCE(pair.key < 0);
+
+		avd->all_cpu_hwprobe_values[key] = pair.value;
+		/*
+		 * Smash together the vendor, arch, and impl IDs to see if
+		 * they're all 0 or any negative.
+		 */
+		if (key <= RISCV_HWPROBE_KEY_MIMPID)
+			id_bitsmash |= pair.value;
+	}
+
+	/*
+	 * If the arch, vendor, and implementation ID are all the same across
+	 * all harts, then assume all CPUs are the same, and allow the vDSO to
+	 * answer queries for arbitrary masks. However if all values are 0 (not
+	 * populated) or any value returns -1 (varies across CPUs), then the
+	 * vDSO should defer to the kernel for exotic cpu masks.
+	 */
+	avd->homogeneous_cpus = (id_bitsmash > 0);
+	return 0;
+}
+
+arch_initcall_sync(init_hwprobe_vdso_data);
+
 SYSCALL_DEFINE5(riscv_hwprobe, uintptr_t, pairs, uintptr_t, pair_count,
 		uintptr_t, cpu_count, uintptr_t, cpus, uintptr_t, flags)
 {
diff --git a/arch/riscv/kernel/vdso/Makefile b/arch/riscv/kernel/vdso/Makefile
index 06e6b27f3bcc..107fd2162cdf 100644
--- a/arch/riscv/kernel/vdso/Makefile
+++ b/arch/riscv/kernel/vdso/Makefile
@@ -12,6 +12,8 @@  vdso-syms += vgettimeofday
 endif
 vdso-syms += getcpu
 vdso-syms += flush_icache
+vdso-syms += hwprobe
+vdso-syms += sys_hwprobe
 
 # Files to link into the vdso
 obj-vdso = $(patsubst %, %.o, $(vdso-syms)) note.o
diff --git a/arch/riscv/kernel/vdso/hwprobe.c b/arch/riscv/kernel/vdso/hwprobe.c
new file mode 100644
index 000000000000..1792d6c30c97
--- /dev/null
+++ b/arch/riscv/kernel/vdso/hwprobe.c
@@ -0,0 +1,47 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2023 Rivos, Inc
+ */
+
+#include <linux/types.h>
+#include <vdso/datapage.h>
+#include <vdso/helpers.h>
+
+extern int riscv_hwprobe(struct riscv_hwprobe *pairs, long pair_count,
+			 long cpu_count, unsigned long *cpus,
+			 unsigned long flags);
+
+int __vdso_riscv_hwprobe(struct riscv_hwprobe *pairs, long pair_count,
+			 long cpu_count, unsigned long *cpus,
+			 unsigned long flags)
+{
+	const struct vdso_data *vd = __arch_get_vdso_data();
+	const struct arch_vdso_data *avd = &vd->arch_data;
+	bool all_cpus = !cpu_count && !cpus;
+	struct riscv_hwprobe *p = pairs;
+	struct riscv_hwprobe *end = pairs + pair_count;
+
+	/*
+	 * Defer to the syscall for exotic requests. The vdso has answers
+	 * stashed away only for the "all cpus" case. If all CPUs are
+	 * homogeneous, then this function can handle requests for arbitrary
+	 * masks.
+	 */
+	if ((flags != 0) || (!all_cpus && !avd->homogeneous_cpus))
+		return riscv_hwprobe(pairs, pair_count, cpu_count, cpus, flags);
+
+	/* This is something we can handle, fill out the pairs. */
+	while (p < end) {
+		if (p->key <= RISCV_HWPROBE_MAX_KEY) {
+			p->value = avd->all_cpu_hwprobe_values[p->key];
+
+		} else {
+			p->key = -1;
+			p->value = 0;
+		}
+
+		p++;
+	}
+
+	return 0;
+}
diff --git a/arch/riscv/kernel/vdso/sys_hwprobe.S b/arch/riscv/kernel/vdso/sys_hwprobe.S
new file mode 100644
index 000000000000..2511c8ba8f86
--- /dev/null
+++ b/arch/riscv/kernel/vdso/sys_hwprobe.S
@@ -0,0 +1,15 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (C) 2022 Rivos, Inc */
+
+#include <linux/linkage.h>
+#include <asm/unistd.h>
+
+.text
+ENTRY(riscv_hwprobe)
+	.cfi_startproc
+	li a7, __NR_riscv_hwprobe
+	ecall
+	ret
+
+	.cfi_endproc
+ENDPROC(riscv_hwprobe)
diff --git a/arch/riscv/kernel/vdso/vdso.lds.S b/arch/riscv/kernel/vdso/vdso.lds.S
index 150b1a572e61..dfe63fb71041 100644
--- a/arch/riscv/kernel/vdso/vdso.lds.S
+++ b/arch/riscv/kernel/vdso/vdso.lds.S
@@ -75,6 +75,7 @@  VERSION
 #endif
 		__vdso_getcpu;
 		__vdso_flush_icache;
+		__vdso_riscv_hwprobe;
 	local: *;
 	};
 }