[PATCH v6 13/19] riscv: Fix race conditions when initializing IPI

Sean Anderson
2020-03-05T18:13:01Z

The IPI code could have race conditions in several places.
* Several harts could race on the value of gd->arch->clint/plic
* Non-boot harts could race with the main hart on the DM subsystem In
addition, if an IPI was pending when U-Boot started, it would cause the
IPI handler to jump to address 0.

To address these problems, a new function riscv_init_ipi is introduced. It
is called once during arch_cpu_init_dm. Before this point, no riscv_*_ipi
functions may be called. Access is synchronized by gd->arch->ipi_ready.

Signed-off-by: Sean Anderson <seanga2@gmail.com>
---

Changes in v6:
- Fix some formatting
- Clear IPIs before enabling interrupts instead of using a ipi_ready flag
- Only print messages on error in smp code

Changes in v5:
- New

arch/riscv/cpu/cpu.c | 6 ++++
arch/riscv/cpu/start.S | 2 ++
arch/riscv/include/asm/smp.h | 43 +++++++++++++++++++++++++++
arch/riscv/lib/andes_plic.c | 34 ++++++++-------------
arch/riscv/lib/sbi_ipi.c | 5 ++++
arch/riscv/lib/sifive_clint.c | 33 +++++++--------------
arch/riscv/lib/smp.c | 56 ++++++++---------------------------
7 files changed, 92 insertions(+), 87 deletions(-)

diff --git a/arch/riscv/cpu/cpu.c b/arch/riscv/cpu/cpu.c
index e457f6acbf..f851374255 100644
--- a/arch/riscv/cpu/cpu.c
+++ b/arch/riscv/cpu/cpu.c
@@ -96,6 +96,12 @@ int arch_cpu_init_dm(void)
csr_write(CSR_SATP, 0);
}

+#ifdef CONFIG_SMP
+ ret = riscv_init_ipi();
+ if (ret)
+ return ret;
+#endif
+
return 0;
}

diff --git a/arch/riscv/cpu/start.S b/arch/riscv/cpu/start.S
index 6b3ff99c38..e8740c8568 100644
--- a/arch/riscv/cpu/start.S
+++ b/arch/riscv/cpu/start.S
@@ -67,6 +67,8 @@ _start:
#else
li t0, SIE_SSIE
#endif
+ /* Clear any pending IPIs */
+ csrc MODE_PREFIX(ip), t0
csrs MODE_PREFIX(ie), t0
#endif

diff --git a/arch/riscv/include/asm/smp.h b/arch/riscv/include/asm/smp.h
index 74de92ed13..1b428856b2 100644
--- a/arch/riscv/include/asm/smp.h
+++ b/arch/riscv/include/asm/smp.h
@@ -51,4 +51,47 @@ void handle_ipi(ulong hart);
*/
int smp_call_function(ulong addr, ulong arg0, ulong arg1, int wait);

+/**
+ * riscv_init_ipi() - Initialize inter-process interrupt (IPI) driver
+ *
+ * Platform code must provide this function. This function is called once after
+ * the cpu driver is initialized. No other riscv_*_ipi() calls will be made
+ * before this function is called.
+ *
+ * @return 0 if OK, -ve on error
+ */
+int riscv_init_ipi(void);
+
+/**
+ * riscv_send_ipi() - Send inter-processor interrupt (IPI)
+ *
+ * Platform code must provide this function.
+ *
+ * @hart: Hart ID of receiving hart
+ * @return 0 if OK, -ve on error
+ */
+int riscv_send_ipi(int hart);
+
+/**
+ * riscv_clear_ipi() - Clear inter-processor interrupt (IPI)
+ *
+ * Platform code must provide this function.
+ *
+ * @hart: Hart ID of hart to be cleared
+ * @return 0 if OK, -ve on error
+ */
+int riscv_clear_ipi(int hart);
+
+/**
+ * riscv_get_ipi() - Get status of inter-processor interrupt (IPI)
+ *
+ * Platform code must provide this function.
+ *
+ * @hart: Hart ID of hart to be checked
+ * @pending: Pointer to variable with result of the check,
+ * 1 if IPI is pending, 0 otherwise
+ * @return 0 if OK, -ve on error
+ */
+int riscv_get_ipi(int hart, int *pending);
+
#endif
diff --git a/arch/riscv/lib/andes_plic.c b/arch/riscv/lib/andes_plic.c
index 20529ab3eb..8484f76386 100644
--- a/arch/riscv/lib/andes_plic.c
+++ b/arch/riscv/lib/andes_plic.c
@@ -30,20 +30,6 @@
#define SEND_IPI_TO_HART(hart) (0x80 >> (hart))

DECLARE_GLOBAL_DATA_PTR;
-static int init_plic(void);
-
-#define PLIC_BASE_GET(void) \
- do { \
- long *ret; \
- \
- if (!gd->arch.plic) { \
- ret = syscon_get_first_range(RISCV_SYSCON_PLIC); \
- if (IS_ERR(ret)) \
- return PTR_ERR(ret); \
- gd->arch.plic = ret; \
- init_plic(); \
- } \
- } while (0)

static int enable_ipi(int hart)
{
@@ -93,13 +79,21 @@ static int init_plic(void)
return -ENODEV;
}

+int riscv_init_ipi(void)
+{
+ int ret = syscon_get_first_range(RISCV_SYSCON_PLIC);
+
+ if (IS_ERR(ret))
+ return PTR_ERR(ret);
+ gd->arch.plic = ret;
+
+ return init_plic();
+}
+
int riscv_send_ipi(int hart)
{
- unsigned int ipi;
+ unsigned int ipi = (SEND_IPI_TO_HART(hart) << (8 * gd->arch.boot_hart));

- PLIC_BASE_GET();
-
- ipi = (SEND_IPI_TO_HART(hart) << (8 * gd->arch.boot_hart));
writel(ipi, (void __iomem *)PENDING_REG(gd->arch.plic,
gd->arch.boot_hart));

@@ -110,8 +104,6 @@ int riscv_clear_ipi(int hart)
{
u32 source_id;

- PLIC_BASE_GET();
-
source_id = readl((void __iomem *)CLAIM_REG(gd->arch.plic, hart));
writel(source_id, (void __iomem *)CLAIM_REG(gd->arch.plic, hart));

@@ -120,8 +112,6 @@ int riscv_clear_ipi(int hart)

int riscv_get_ipi(int hart, int *pending)
{
- PLIC_BASE_GET();
-
*pending = readl((void __iomem *)PENDING_REG(gd->arch.plic,
gd->arch.boot_hart));
*pending = !!(*pending & SEND_IPI_TO_HART(hart));
diff --git a/arch/riscv/lib/sbi_ipi.c b/arch/riscv/lib/sbi_ipi.c
index 9a698ce74e..310d1bd2a4 100644
--- a/arch/riscv/lib/sbi_ipi.c
+++ b/arch/riscv/lib/sbi_ipi.c
@@ -7,6 +7,11 @@
#include <common.h>
#include <asm/sbi.h>

+int riscv_init_ipi(void)
+{
+ return 0;
+}
+
int riscv_send_ipi(int hart)
{
ulong mask;
diff --git a/arch/riscv/lib/sifive_clint.c b/arch/riscv/lib/sifive_clint.c
index 5e0d25720b..78fc6c868d 100644
--- a/arch/riscv/lib/sifive_clint.c
+++ b/arch/riscv/lib/sifive_clint.c
@@ -24,22 +24,8 @@

DECLARE_GLOBAL_DATA_PTR;

-#define CLINT_BASE_GET(void) \
- do { \
- long *ret; \
- \
- if (!gd->arch.clint) { \
- ret = syscon_get_first_range(RISCV_SYSCON_CLINT); \
- if (IS_ERR(ret)) \
- return PTR_ERR(ret); \
- gd->arch.clint = ret; \
- } \
- } while (0)
-
int riscv_get_time(u64 *time)
{
- CLINT_BASE_GET();
-
*time = readq((void __iomem *)MTIME_REG(gd->arch.clint));

return 0;
@@ -47,17 +33,24 @@ int riscv_get_time(u64 *time)

int riscv_set_timecmp(int hart, u64 cmp)
{
- CLINT_BASE_GET();
-
writeq(cmp, (void __iomem *)MTIMECMP_REG(gd->arch.clint, hart));

return 0;
}

+int riscv_init_ipi(void)
+{
+ long *ret = syscon_get_first_range(RISCV_SYSCON_CLINT);
+
+ if (IS_ERR(ret))
+ return PTR_ERR(ret);
+ gd->arch.clint = ret;
+
+ return 0;
+}
+
int riscv_send_ipi(int hart)
{
- CLINT_BASE_GET();
-
writel(1, (void __iomem *)MSIP_REG(gd->arch.clint, hart));

return 0;
@@ -65,8 +58,6 @@ int riscv_send_ipi(int hart)

int riscv_clear_ipi(int hart)
{
- CLINT_BASE_GET();
-
writel(0, (void __iomem *)MSIP_REG(gd->arch.clint, hart));

return 0;
@@ -74,8 +65,6 @@ int riscv_clear_ipi(int hart)

int riscv_get_ipi(int hart, int *pending)
{
- CLINT_BASE_GET();
-
*pending = readl((void __iomem *)MSIP_REG(gd->arch.clint, hart));

return 0;
diff --git a/arch/riscv/lib/smp.c b/arch/riscv/lib/smp.c
index 17adb35730..fe992eb00f 100644
--- a/arch/riscv/lib/smp.c
+++ b/arch/riscv/lib/smp.c
@@ -12,38 +12,6 @@

DECLARE_GLOBAL_DATA_PTR;

-/**
- * riscv_send_ipi() - Send inter-processor interrupt (IPI)
- *
- * Platform code must provide this function.
- *
- * @hart: Hart ID of receiving hart
- * @return 0 if OK, -ve on error
- */
-extern int riscv_send_ipi(int hart);
-
-/**
- * riscv_clear_ipi() - Clear inter-processor interrupt (IPI)
- *
- * Platform code must provide this function.
- *
- * @hart: Hart ID of hart to be cleared
- * @return 0 if OK, -ve on error
- */
-extern int riscv_clear_ipi(int hart);
-
-/**
- * riscv_get_ipi() - Get status of inter-processor interrupt (IPI)
- *
- * Platform code must provide this function.
- *
- * @hart: Hart ID of hart to be checked
- * @pending: Pointer to variable with result of the check,
- * 1 if IPI is pending, 0 otherwise
- * @return 0 if OK, -ve on error
- */
-extern int riscv_get_ipi(int hart, int *pending);
-
static int send_ipi_many(struct ipi_data *ipi, int wait)
{
ofnode node, cpus;
@@ -114,7 +82,6 @@ void handle_ipi(ulong hart)
return;

__smp_mb();
-
smp_function = (void (*)(ulong, ulong, ulong))gd->arch.ipi[hart].addr;
invalidate_icache_all();

@@ -124,7 +91,13 @@ void handle_ipi(ulong hart)
*/
ret = riscv_clear_ipi(hart);
if (ret) {
- pr_err("Cannot clear IPI of hart %ld\n", hart);
+ pr_err("Cannot clear IPI of hart %ld (error %d)\n", hart, ret);
+ return;
+ }
+
+ /* Sanity check */
+ if (!smp_function) {
+ pr_err("smp_function is NULL on hart %ld\n", hart);
return;
}

@@ -133,14 +106,11 @@ void handle_ipi(ulong hart)

int smp_call_function(ulong addr, ulong arg0, ulong arg1, int wait)
{
- int ret = 0;
- struct ipi_data ipi;
+ struct ipi_data ipi = {
+ .addr = addr,
+ .arg0 = arg0,
+ .arg1 = arg1,
+ };

- ipi.addr = addr;
- ipi.arg0 = arg0;
- ipi.arg1 = arg1;
-
- ret = send_ipi_many(&ipi, wait);
-
- return ret;
+ return send_ipi_many(&ipi, wait);
}
--
2.25.0