diff mbox series

[v8,5/7] xen/riscv: introduce and initialize SBI RFENCE extension

Message ID c3aba0520f0dc01fcd4e4b6d5e0e9b7a51d44aad.1727449154.git.oleksii.kurochko@gmail.com (mailing list archive)
State Superseded
Headers show
Series device tree mapping | expand

Commit Message

Oleksii Kurochko Sept. 27, 2024, 4:33 p.m. UTC
Introduce functions to work with the SBI RFENCE extension for issuing
various fence operations to remote CPUs.

Add the sbi_init() function along with auxiliary functions and macro
definitions for proper initialization and checking the availability of
SBI extensions. Currently, this is implemented only for RFENCE.

Introduce sbi_remote_sfence_vma() to send SFENCE_VMA instructions to
a set of target HARTs. This will support the implementation of
flush_xen_tlb_range_va().

Integrate __sbi_rfence_v02 from Linux kernel 6.6.0-rc4 with minimal
modifications:
 - Adapt to Xen code style.
 - Use cpuid_to_hartid() instead of cpuid_to_hartid_map[].
 - Update BIT(...) to BIT(..., UL).
 - Rename __sbi_rfence_v02_call to sbi_rfence_v02_real and
   remove the unused arg5.
 - Handle NULL cpu_mask to execute rfence on all CPUs by calling
   sbi_rfence_v02_real(..., 0UL, -1UL,...) instead of creating hmask.
 - change type for start_addr and size to vaddr_t and size_t.
 - Add an explanatory comment about when batching can and cannot occur,
   and why batching happens in the first place.

Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
---
 xen/arch/riscv/include/asm/sbi.h |  62 +++++++
 xen/arch/riscv/sbi.c             | 273 ++++++++++++++++++++++++++++++-
 xen/arch/riscv/setup.c           |   3 +
 3 files changed, 337 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/xen/arch/riscv/include/asm/sbi.h b/xen/arch/riscv/include/asm/sbi.h
index 4d72a2295e..5947fed779 100644
--- a/xen/arch/riscv/include/asm/sbi.h
+++ b/xen/arch/riscv/include/asm/sbi.h
@@ -12,9 +12,42 @@ 
 #ifndef __ASM_RISCV_SBI_H__
 #define __ASM_RISCV_SBI_H__
 
+#include <xen/cpumask.h>
+
 #define SBI_EXT_0_1_CONSOLE_PUTCHAR		0x1
 #define SBI_EXT_0_1_SHUTDOWN			0x8
 
+#define SBI_EXT_BASE                    0x10
+#define SBI_EXT_RFENCE                  0x52464E43
+
+/* SBI function IDs for BASE extension */
+#define SBI_EXT_BASE_GET_SPEC_VERSION   0x0
+#define SBI_EXT_BASE_GET_IMP_ID         0x1
+#define SBI_EXT_BASE_GET_IMP_VERSION    0x2
+#define SBI_EXT_BASE_PROBE_EXT          0x3
+
+/* SBI function IDs for RFENCE extension */
+#define SBI_EXT_RFENCE_REMOTE_FENCE_I           0x0
+#define SBI_EXT_RFENCE_REMOTE_SFENCE_VMA        0x1
+#define SBI_EXT_RFENCE_REMOTE_SFENCE_VMA_ASID   0x2
+#define SBI_EXT_RFENCE_REMOTE_HFENCE_GVMA       0x3
+#define SBI_EXT_RFENCE_REMOTE_HFENCE_GVMA_VMID  0x4
+#define SBI_EXT_RFENCE_REMOTE_HFENCE_VVMA       0x5
+#define SBI_EXT_RFENCE_REMOTE_HFENCE_VVMA_ASID  0x6
+
+#define SBI_SPEC_VERSION_MAJOR_MASK     0x7f000000
+#define SBI_SPEC_VERSION_MINOR_MASK     0x00ffffff
+
+/* SBI return error codes */
+#define SBI_SUCCESS             0
+#define SBI_ERR_FAILURE         (-1)
+#define SBI_ERR_NOT_SUPPORTED   (-2)
+#define SBI_ERR_INVALID_PARAM   (-3)
+#define SBI_ERR_DENIED          (-4)
+#define SBI_ERR_INVALID_ADDRESS (-5)
+
+#define SBI_SPEC_VERSION_DEFAULT 0x1
+
 struct sbiret {
     long error;
     long value;
@@ -34,4 +67,33 @@  void sbi_console_putchar(int ch);
 
 void sbi_shutdown(void);
 
+/*
+ * Check underlying SBI implementation has RFENCE
+ *
+ * @return true for supported AND false for not-supported
+ */
+bool sbi_has_rfence(void);
+
+/*
+ * Instructs the remote harts to execute one or more SFENCE.VMA
+ * instructions, covering the range of virtual addresses between
+ * [start_addr, start_addr + size).
+ *
+ * Returns 0 if IPI was sent to all the targeted harts successfully
+ * or negative value if start_addr or size is not valid.
+ *
+ * @hart_mask a cpu mask containing all the target harts.
+ * @param start virtual address start
+ * @param size virtual address range size
+ */
+int sbi_remote_sfence_vma(const cpumask_t *cpu_mask, vaddr_t start,
+                          size_t size);
+
+/*
+ * Initialize SBI library
+ *
+ * @return 0 on success, otherwise negative errno on failure
+ */
+int sbi_init(void);
+
 #endif /* __ASM_RISCV_SBI_H__ */
diff --git a/xen/arch/riscv/sbi.c b/xen/arch/riscv/sbi.c
index c7984344bc..4209520389 100644
--- a/xen/arch/riscv/sbi.c
+++ b/xen/arch/riscv/sbi.c
@@ -5,13 +5,26 @@ 
  * (anup.patel@wdc.com).
  *
  * Modified by Bobby Eshleman (bobby.eshleman@gmail.com).
+ * Modified by Oleksii Kurochko (oleksii.kurochko@gmail.com).
  *
  * Copyright (c) 2019 Western Digital Corporation or its affiliates.
- * Copyright (c) 2021-2023 Vates SAS.
+ * Copyright (c) 2021-2024 Vates SAS.
  */
 
+#include <xen/compiler.h>
+#include <xen/const.h>
+#include <xen/cpumask.h>
+#include <xen/errno.h>
+#include <xen/init.h>
+#include <xen/lib.h>
+#include <xen/sections.h>
+#include <xen/smp.h>
+
+#include <asm/processor.h>
 #include <asm/sbi.h>
 
+static unsigned long __ro_after_init sbi_spec_version = SBI_SPEC_VERSION_DEFAULT;
+
 struct sbiret sbi_ecall(unsigned long ext, unsigned long fid,
                         unsigned long arg0, unsigned long arg1,
                         unsigned long arg2, unsigned long arg3,
@@ -38,6 +51,26 @@  struct sbiret sbi_ecall(unsigned long ext, unsigned long fid,
     return ret;
 }
 
+static int sbi_err_map_xen_errno(int err)
+{
+    switch ( err )
+    {
+    case SBI_SUCCESS:
+        return 0;
+    case SBI_ERR_DENIED:
+        return -EACCES;
+    case SBI_ERR_INVALID_PARAM:
+        return -EINVAL;
+    case SBI_ERR_INVALID_ADDRESS:
+        return -EFAULT;
+    case SBI_ERR_NOT_SUPPORTED:
+        return -EOPNOTSUPP;
+    case SBI_ERR_FAILURE:
+    default:
+        return -ENOSYS;
+    };
+}
+
 void sbi_console_putchar(int ch)
 {
     sbi_ecall(SBI_EXT_0_1_CONSOLE_PUTCHAR, 0, ch, 0, 0, 0, 0, 0);
@@ -47,3 +80,241 @@  void sbi_shutdown(void)
 {
     sbi_ecall(SBI_EXT_0_1_SHUTDOWN, 0, 0, 0, 0, 0, 0, 0);
 }
+
+static unsigned int sbi_major_version(void)
+{
+    return MASK_EXTR(sbi_spec_version, SBI_SPEC_VERSION_MAJOR_MASK);
+}
+
+static unsigned int sbi_minor_version(void)
+{
+    return MASK_EXTR(sbi_spec_version, SBI_SPEC_VERSION_MINOR_MASK);
+}
+
+static long sbi_ext_base_func(long fid)
+{
+    struct sbiret ret;
+
+    ret = sbi_ecall(SBI_EXT_BASE, fid, 0, 0, 0, 0, 0, 0);
+
+    if ( !ret.error )
+    {
+        /*
+         * I wasn't able to find a case in the SBI spec where sbiret.value
+         * could be negative.
+         *
+         * Unfortunately, the spec does not specify the possible values of
+         * sbiret.value, but based on the description of the SBI function,
+         * ret.value >= 0 when sbiret.error = 0. SPI spec specify only
+         * possible value for sbiret.error (<= 0 whwere 0 is SBI_SUCCESS ).
+         *
+         * Just to be sure that SBI base extension functions one day won't
+         * start to return a negative value for sbiret.value when
+         * sbiret.error < 0 BUG_ON() is added.
+         */
+        BUG_ON(ret.value < 0);
+
+        return ret.value;
+    }
+    else
+        return ret.error;
+}
+
+static int sbi_rfence_v02_real(unsigned long fid,
+                               unsigned long hmask, unsigned long hbase,
+                               vaddr_t start, size_t size,
+                               unsigned long arg4)
+{
+    struct sbiret ret = {0};
+    int result = 0;
+
+    switch ( fid )
+    {
+    case SBI_EXT_RFENCE_REMOTE_FENCE_I:
+        ret = sbi_ecall(SBI_EXT_RFENCE, fid, hmask, hbase,
+                        0, 0, 0, 0);
+        break;
+
+    case SBI_EXT_RFENCE_REMOTE_HFENCE_GVMA:
+    case SBI_EXT_RFENCE_REMOTE_HFENCE_VVMA:
+    case SBI_EXT_RFENCE_REMOTE_SFENCE_VMA:
+        ret = sbi_ecall(SBI_EXT_RFENCE, fid, hmask, hbase,
+                        start, size, 0, 0);
+        break;
+
+    case SBI_EXT_RFENCE_REMOTE_SFENCE_VMA_ASID:
+    case SBI_EXT_RFENCE_REMOTE_HFENCE_GVMA_VMID:
+    case SBI_EXT_RFENCE_REMOTE_HFENCE_VVMA_ASID:
+        ret = sbi_ecall(SBI_EXT_RFENCE, fid, hmask, hbase,
+                        start, size, arg4, 0);
+        break;
+
+    default:
+        printk("%s: unknown function ID [%#lx]\n",
+               __func__, fid);
+        result = -EINVAL;
+        break;
+    };
+
+    if ( ret.error )
+    {
+        result = sbi_err_map_xen_errno(ret.error);
+        printk("%s: hbase=%lu hmask=%#lx failed (error %ld)\n",
+               __func__, hbase, hmask, ret.error);
+    }
+
+    return result;
+}
+
+static int cf_check sbi_rfence_v02(unsigned long fid,
+                                   const cpumask_t *cpu_mask,
+                                   vaddr_t start, size_t size,
+                                   unsigned long arg4, unsigned long arg5)
+{
+    unsigned long hartid, cpuid, hmask = 0, hbase = 0, htop = 0;
+    int result = -EINVAL;
+
+    /*
+     * hart_mask_base can be set to -1 to indicate that hart_mask can be
+     * ignored and all available harts must be considered.
+     */
+    if ( !cpu_mask )
+        return sbi_rfence_v02_real(fid, 0UL, -1UL, start, size, arg4);
+
+    for_each_cpu ( cpuid, cpu_mask )
+    {
+        /*
+         * Hart IDs might not necessarily be numbered contiguously in
+         * a multiprocessor system.
+         *
+         * This means that it is possible for the hart ID mapping to look like:
+         *  0, 1, 3, 65, 66, 69
+         * In such cases, more than one call to sbi_rfence_v02_real() will be
+         * needed, as a single hmask can only cover sizeof(unsigned long) CPUs:
+         *  1. sbi_rfence_v02_real(hmask=0b1011, hbase=0)
+         *  2. sbi_rfence_v02_real(hmask=0b1011, hbase=65)
+         *
+         * The algorithm below tries to batch as many harts as possible before
+         * making an SBI call. However, batching may not always be possible.
+         * For example, consider the hart ID mapping:
+         *   0, 64, 1, 65, 2, 66 (1)
+         *
+         * Generally, batching is also possible for (1):
+         *    First (0,1,2), then (64,65,66).
+         * It just requires a different approach and updates to the current
+         * algorithm.
+         */
+        hartid = cpuid_to_hartid(cpuid);
+        if ( hmask )
+        {
+            if ( hartid + BITS_PER_LONG <= htop ||
+                 hbase + BITS_PER_LONG <= hartid )
+            {
+                result = sbi_rfence_v02_real(fid, hmask, hbase,
+                                             start, size, arg4);
+                hmask = 0;
+                if ( result )
+                    break;
+            }
+            else if ( hartid < hbase )
+            {
+                /* shift the mask to fit lower hartid */
+                hmask <<= hbase - hartid;
+                hbase = hartid;
+            }
+        }
+
+        if ( !hmask )
+        {
+            hbase = hartid;
+            htop = hartid;
+        }
+        else if ( hartid > htop )
+            htop = hartid;
+
+        hmask |= BIT(hartid - hbase, UL);
+    }
+
+    if ( hmask )
+        result = sbi_rfence_v02_real(fid, hmask, hbase,
+                                     start, size, arg4);
+
+    return result;
+}
+
+static int (* __ro_after_init sbi_rfence)(unsigned long fid,
+                                          const cpumask_t *cpu_mask,
+                                          vaddr_t start,
+                                          size_t size,
+                                          unsigned long arg4,
+                                          unsigned long arg5);
+
+int sbi_remote_sfence_vma(const cpumask_t *cpu_mask, vaddr_t start,
+                          size_t size)
+{
+    ASSERT(sbi_rfence);
+
+    return sbi_rfence(SBI_EXT_RFENCE_REMOTE_SFENCE_VMA,
+                      cpu_mask, start, size, 0, 0);
+}
+
+/* This function must always succeed. */
+#define sbi_get_spec_version()  \
+    sbi_ext_base_func(SBI_EXT_BASE_GET_SPEC_VERSION)
+
+#define sbi_get_firmware_id()   \
+    sbi_ext_base_func(SBI_EXT_BASE_GET_IMP_ID)
+
+#define sbi_get_firmware_version()  \
+    sbi_ext_base_func(SBI_EXT_BASE_GET_IMP_VERSION)
+
+int sbi_probe_extension(long extid)
+{
+    struct sbiret ret;
+
+    ret = sbi_ecall(SBI_EXT_BASE, SBI_EXT_BASE_PROBE_EXT, extid,
+                    0, 0, 0, 0, 0);
+    if ( !ret.error && ret.value )
+        return ret.value;
+
+    return sbi_err_map_xen_errno(ret.error);
+}
+
+static bool sbi_spec_is_0_1(void)
+{
+    return (sbi_spec_version == SBI_SPEC_VERSION_DEFAULT);
+}
+
+bool sbi_has_rfence(void)
+{
+    return (sbi_rfence != NULL);
+}
+
+int __init sbi_init(void)
+{
+    sbi_spec_version = sbi_get_spec_version();
+
+    printk("SBI specification v%u.%u detected\n",
+            sbi_major_version(), sbi_minor_version());
+
+    if ( !sbi_spec_is_0_1() )
+    {
+        long sbi_fw_id = sbi_get_firmware_id();
+        long sbi_fw_version = sbi_get_firmware_version();
+
+        BUG_ON((sbi_fw_id < 0) || (sbi_fw_version < 0));
+
+        printk("SBI implementation ID=%#lx Version=%#lx\n",
+            sbi_fw_id, sbi_fw_version);
+
+        if ( sbi_probe_extension(SBI_EXT_RFENCE) > 0 )
+        {
+            sbi_rfence = sbi_rfence_v02;
+            printk("SBI v0.2 RFENCE extension detected\n");
+        }
+    }
+    else
+        panic("Ooops. SBI spec version 0.1 detected. Need to add support");
+
+    return 0;
+}
diff --git a/xen/arch/riscv/setup.c b/xen/arch/riscv/setup.c
index 6e3a787dbe..c4fadd36c6 100644
--- a/xen/arch/riscv/setup.c
+++ b/xen/arch/riscv/setup.c
@@ -9,6 +9,7 @@ 
 #include <public/version.h>
 
 #include <asm/early_printk.h>
+#include <asm/sbi.h>
 #include <asm/smp.h>
 #include <asm/traps.h>
 
@@ -48,6 +49,8 @@  void __init noreturn start_xen(unsigned long bootcpu_id,
 
     trap_init();
 
+    sbi_init();
+
 #ifdef CONFIG_SELF_TESTS
     test_macros_from_bug_h();
 #endif