diff mbox series

[kvm-unit-tests,3/7] powerpc: abstract H_CEDE calls into a sleep() function

Message ID 20230317123614.3687163-3-npiggin@gmail.com (mailing list archive)
State New, archived
Headers show
Series [kvm-unit-tests,1/7] MAINTAINERS: Update powerpc list | expand

Commit Message

Nicholas Piggin March 17, 2023, 12:36 p.m. UTC 
This consolidates several implementations, and it no longer leaves
MSR[EE] enabled after the decrementer interrupt is handled, but
rather disables it on return.

The handler no longer allows a continuous ticking, but rather dec
has to be re-armed and EE re-enabled (e.g., via H_CEDE hcall) each
time.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 lib/powerpc/asm/handlers.h  |  2 +-
 lib/powerpc/asm/ppc_asm.h   |  1 +
 lib/powerpc/asm/processor.h |  1 +
 lib/powerpc/handlers.c      | 10 ++++------
 lib/powerpc/processor.c     | 31 +++++++++++++++++++++++++++++++
 powerpc/sprs.c              |  6 +-----
 powerpc/tm.c                | 20 +-------------------
 7 files changed, 40 insertions(+), 31 deletions(-)

Comments

Thomas Huth March 17, 2023, 1:01 p.m. UTC | #1 
On 17/03/2023 13.36, Nicholas Piggin wrote:
> This consolidates several implementations, and it no longer leaves
> MSR[EE] enabled after the decrementer interrupt is handled, but
> rather disables it on return.
> 
> The handler no longer allows a continuous ticking, but rather dec
> has to be re-armed and EE re-enabled (e.g., via H_CEDE hcall) each
> time.
> 
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> ---
...
> diff --git a/lib/powerpc/processor.c b/lib/powerpc/processor.c
> index ec85b9d..f1fb50f 100644
> --- a/lib/powerpc/processor.c
> +++ b/lib/powerpc/processor.c
> @@ -10,6 +10,8 @@
>   #include <asm/ptrace.h>
>   #include <asm/setup.h>
>   #include <asm/barrier.h>
> +#include <asm/hcall.h>
> +#include <asm/handlers.h>
>   
>   static struct {
>   	void (*func)(struct pt_regs *, void *data);
> @@ -54,3 +56,32 @@ void udelay(uint64_t us)
>   {
>   	delay((us * tb_hz) / 1000000);
>   }
> +
> +void sleep(uint64_t cycles)

When I see a sleep() in a C program, I automatically assume that it's 
parameter is "seconds", so having a sleep() function here that is taking 
cycles as a parameter is confusing. Could you please name the function 
differently?

> +{
> +	uint64_t start, end, now;
> +
> +	start = now = get_tb();
> +	end = start + cycles;
> +
> +	while (end > now) {
> +		uint64_t left = end - now;
> +
> +		/* Could support large decrementer */
> +		if (left > 0x7fffffff)
> +			left = 0x7fffffff;
> +
> +		asm volatile ("mtdec %0" : : "r" (left));
> +		handle_exception(0x900, &dec_handler_oneshot, NULL);
> +		if (hcall(H_CEDE) != H_SUCCESS) {
> +			printf("H_CEDE failed\n");
> +			abort();
> +		}
> +		handle_exception(0x900, NULL, NULL);
> +
> +		if (left < 0x7fffffff)
> +			break;

Shouldn't that be covered by the "end > now" in the while loop condition 
check already?

> +		now = get_tb();
> +	}
> +}

  Thomas
diff mbox series

Patch

diff --git a/lib/powerpc/asm/handlers.h b/lib/powerpc/asm/handlers.h
index 64ba727..e4a0cd4 100644
--- a/lib/powerpc/asm/handlers.h
+++ b/lib/powerpc/asm/handlers.h
@@ -3,6 +3,6 @@ 
 
 #include <asm/ptrace.h>
 
-void dec_except_handler(struct pt_regs *regs, void *data);
+void dec_handler_oneshot(struct pt_regs *regs, void *data);
 
 #endif /* _ASMPOWERPC_HANDLERS_H_ */
diff --git a/lib/powerpc/asm/ppc_asm.h b/lib/powerpc/asm/ppc_asm.h
index 1b85f6b..6299ff5 100644
--- a/lib/powerpc/asm/ppc_asm.h
+++ b/lib/powerpc/asm/ppc_asm.h
@@ -36,6 +36,7 @@ 
 #endif /* __BYTE_ORDER__ */
 
 /* Machine State Register definitions: */
+#define MSR_EE_BIT	15			/* External Interrupts Enable */
 #define MSR_SF_BIT	63			/* 64-bit mode */
 
 #endif /* _ASMPOWERPC_PPC_ASM_H */
diff --git a/lib/powerpc/asm/processor.h b/lib/powerpc/asm/processor.h
index ac001e1..1467f2c 100644
--- a/lib/powerpc/asm/processor.h
+++ b/lib/powerpc/asm/processor.h
@@ -20,6 +20,7 @@  static inline uint64_t get_tb(void)
 
 extern void delay(uint64_t cycles);
 extern void udelay(uint64_t us);
+extern void sleep(uint64_t cycles);
 
 static inline void mdelay(uint64_t ms)
 {
diff --git a/lib/powerpc/handlers.c b/lib/powerpc/handlers.c
index c8721e0..296f14f 100644
--- a/lib/powerpc/handlers.c
+++ b/lib/powerpc/handlers.c
@@ -9,15 +9,13 @@ 
 #include <libcflat.h>
 #include <asm/handlers.h>
 #include <asm/ptrace.h>
+#include <asm/ppc_asm.h>
 
 /*
  * Generic handler for decrementer exceptions (0x900)
- * Just reset the decrementer back to the value specified when registering the
- * handler
+ * Return with MSR[EE] disabled.
  */
-void dec_except_handler(struct pt_regs *regs __unused, void *data)
+void dec_handler_oneshot(struct pt_regs *regs, void *data)
 {
-	uint64_t dec = *((uint64_t *) data);
-
-	asm volatile ("mtdec %0" : : "r" (dec));
+	regs->msr &= ~(1UL << MSR_EE_BIT);
 }
diff --git a/lib/powerpc/processor.c b/lib/powerpc/processor.c
index ec85b9d..f1fb50f 100644
--- a/lib/powerpc/processor.c
+++ b/lib/powerpc/processor.c
@@ -10,6 +10,8 @@ 
 #include <asm/ptrace.h>
 #include <asm/setup.h>
 #include <asm/barrier.h>
+#include <asm/hcall.h>
+#include <asm/handlers.h>
 
 static struct {
 	void (*func)(struct pt_regs *, void *data);
@@ -54,3 +56,32 @@  void udelay(uint64_t us)
 {
 	delay((us * tb_hz) / 1000000);
 }
+
+void sleep(uint64_t cycles)
+{
+	uint64_t start, end, now;
+
+	start = now = get_tb();
+	end = start + cycles;
+
+	while (end > now) {
+		uint64_t left = end - now;
+
+		/* Could support large decrementer */
+		if (left > 0x7fffffff)
+			left = 0x7fffffff;
+
+		asm volatile ("mtdec %0" : : "r" (left));
+		handle_exception(0x900, &dec_handler_oneshot, NULL);
+		if (hcall(H_CEDE) != H_SUCCESS) {
+			printf("H_CEDE failed\n");
+			abort();
+		}
+		handle_exception(0x900, NULL, NULL);
+
+		if (left < 0x7fffffff)
+			break;
+
+		now = get_tb();
+	}
+}
diff --git a/powerpc/sprs.c b/powerpc/sprs.c
index 5cc1cd1..161a6ba 100644
--- a/powerpc/sprs.c
+++ b/powerpc/sprs.c
@@ -254,7 +254,6 @@  int main(int argc, char **argv)
 		0x1234567890ABCDEFULL, 0xFEDCBA0987654321ULL,
 		-1ULL,
 	};
-	static uint64_t decr = 0x7FFFFFFF; /* Max value */
 
 	for (i = 1; i < argc; i++) {
 		if (!strcmp(argv[i], "-w")) {
@@ -288,10 +287,7 @@  int main(int argc, char **argv)
 	if (pause) {
 		migrate_once();
 	} else {
-		puts("Sleeping...\n");
-		handle_exception(0x900, &dec_except_handler, &decr);
-		asm volatile ("mtdec %0" : : "r" (0x3FFFFFFF));
-		hcall(H_CEDE);
+		sleep(0x10000000);
 	}
 
 	get_sprs(after);
diff --git a/powerpc/tm.c b/powerpc/tm.c
index 65cacdf..61bacf4 100644
--- a/powerpc/tm.c
+++ b/powerpc/tm.c
@@ -48,17 +48,6 @@  static int count_cpus_with_tm(void)
 	return available;
 }
 
-static int h_cede(void)
-{
-	register uint64_t r3 asm("r3") = H_CEDE;
-
-	asm volatile ("sc 1" : "+r"(r3) :
-			     : "r0", "r4", "r5", "r6", "r7", "r8", "r9",
-			       "r10", "r11", "r12", "xer", "ctr", "cc");
-
-	return r3;
-}
-
 /*
  * Enable transactional memory
  * Returns:	FALSE - Failure
@@ -95,14 +84,10 @@  static bool enable_tm(void)
 static void test_h_cede_tm(int argc, char **argv)
 {
 	int i;
-	static uint64_t decr = 0x3FFFFF; /* ~10ms */
 
 	if (argc > 2)
 		report_abort("Unsupported argument: '%s'", argv[2]);
 
-	handle_exception(0x900, &dec_except_handler, &decr);
-	asm volatile ("mtdec %0" : : "r" (decr));
-
 	if (!start_all_cpus(halt, 0))
 		report_abort("Failed to start secondary cpus");
 
@@ -120,10 +105,7 @@  static void test_h_cede_tm(int argc, char **argv)
 		      "bf 2,1b" : : : "cr0");
 
 	for (i = 0; i < 500; i++) {
-		uint64_t rval = h_cede();
-
-		if (rval != H_SUCCESS)
-			break;
+		sleep(0x3FFFFF); /* ~10ms */
 		mdelay(5);
 	}