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[Qemu-devel] [PATCH v5 01/13] target/arm: Reorganize PMCCNTR accesses
From: |
Aaron Lindsay |
Subject: |
[Qemu-devel] [PATCH v5 01/13] target/arm: Reorganize PMCCNTR accesses |
Date: |
Fri, 22 Jun 2018 16:32:15 -0400 |
pmccntr_read and pmccntr_write contained duplicate code that was already
being handled by pmccntr_sync. Consolidate the duplicated code into two
functions: pmccntr_op_start and pmccntr_op_finish. Add a companion to
c15_ccnt in CPUARMState so that we can simultaneously save both the
architectural register value and the last underlying cycle count - this
ensure time isn't lost and will also allow us to access the 'old'
architectural register value in order to detect overflows in later
patches.
Signed-off-by: Aaron Lindsay <address@hidden>
---
target/arm/cpu.h | 28 ++++++++++-----
target/arm/helper.c | 100 ++++++++++++++++++++++++++++------------------------
2 files changed, 73 insertions(+), 55 deletions(-)
diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index 8488273..ba2c876 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -467,10 +467,20 @@ typedef struct CPUARMState {
uint64_t oslsr_el1; /* OS Lock Status */
uint64_t mdcr_el2;
uint64_t mdcr_el3;
- /* If the counter is enabled, this stores the last time the counter
- * was reset. Otherwise it stores the counter value
+ /* Stores the architectural value of the counter *the last time it was
+ * updated* by pmccntr_op_start. Accesses should always be surrounded
+ * by pmccntr_op_start/pmccntr_op_finish to guarantee the latest
+ * architecturally-corect value is being read/set.
*/
uint64_t c15_ccnt;
+ /* Stores the delta between the architectural value and the underlying
+ * cycle count during normal operation. It is used to update c15_ccnt
+ * to be the correct architectural value before accesses. During
+ * accesses, c15_ccnt_delta contains the underlying count being used
+ * for the access, after which it reverts to the delta value in
+ * pmccntr_op_finish.
+ */
+ uint64_t c15_ccnt_delta;
uint64_t pmccfiltr_el0; /* Performance Monitor Filter Register */
uint64_t vpidr_el2; /* Virtualization Processor ID Register */
uint64_t vmpidr_el2; /* Virtualization Multiprocessor ID Register */
@@ -924,15 +934,17 @@ int cpu_arm_signal_handler(int host_signum, void *pinfo,
void *puc);
/**
- * pmccntr_sync
+ * pmccntr_op_start/finish
* @env: CPUARMState
*
- * Synchronises the counter in the PMCCNTR. This must always be called twice,
- * once before any action that might affect the timer and again afterwards.
- * The function is used to swap the state of the register if required.
- * This only happens when not in user mode (!CONFIG_USER_ONLY)
+ * Convert the counter in the PMCCNTR between its delta form (the typical mode
+ * when it's enabled) and the guest-visible value. These two calls must always
+ * surround any action which might affect the counter, and the return value
+ * from pmccntr_op_start must be supplied as the second argument to
+ * pmccntr_op_finish.
*/
-void pmccntr_sync(CPUARMState *env);
+void pmccntr_op_start(CPUARMState *env);
+void pmccntr_op_finish(CPUARMState *env);
/* SCTLR bit meanings. Several bits have been reused in newer
* versions of the architecture; in that case we define constants
diff --git a/target/arm/helper.c b/target/arm/helper.c
index 1248d84..23b3a16 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -1044,28 +1044,53 @@ static inline bool arm_ccnt_enabled(CPUARMState *env)
return true;
}
-
-void pmccntr_sync(CPUARMState *env)
+/*
+ * Ensure c15_ccnt is the guest-visible count so that operations such as
+ * enabling/disabling the counter or filtering, modifying the count itself,
+ * etc. can be done logically. This is essentially a no-op if the counter is
+ * not enabled at the time of the call.
+ */
+void pmccntr_op_start(CPUARMState *env)
{
- uint64_t temp_ticks;
-
- temp_ticks = muldiv64(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL),
+ uint64_t cycles = 0;
+ cycles = muldiv64(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL),
ARM_CPU_FREQ, NANOSECONDS_PER_SECOND);
- if (env->cp15.c9_pmcr & PMCRD) {
- /* Increment once every 64 processor clock cycles */
- temp_ticks /= 64;
- }
-
if (arm_ccnt_enabled(env)) {
- env->cp15.c15_ccnt = temp_ticks - env->cp15.c15_ccnt;
+ uint64_t eff_cycles = cycles;
+ if (env->cp15.c9_pmcr & PMCRD) {
+ /* Increment once every 64 processor clock cycles */
+ eff_cycles /= 64;
+ }
+
+ env->cp15.c15_ccnt = eff_cycles - env->cp15.c15_ccnt_delta;
+ }
+ env->cp15.c15_ccnt_delta = cycles;
+}
+
+/*
+ * If PMCCNTR is enabled, recalculate the delta between the clock and the
+ * guest-visible count. A call to pmccntr_op_finish should follow every call to
+ * pmccntr_op_start.
+ */
+void pmccntr_op_finish(CPUARMState *env)
+{
+ if (arm_ccnt_enabled(env)) {
+ uint64_t prev_cycles = env->cp15.c15_ccnt_delta;
+
+ if (env->cp15.c9_pmcr & PMCRD) {
+ /* Increment once every 64 processor clock cycles */
+ prev_cycles /= 64;
+ }
+
+ env->cp15.c15_ccnt_delta = prev_cycles - env->cp15.c15_ccnt;
}
}
static void pmcr_write(CPUARMState *env, const ARMCPRegInfo *ri,
uint64_t value)
{
- pmccntr_sync(env);
+ pmccntr_op_start(env);
if (value & PMCRC) {
/* The counter has been reset */
@@ -1076,26 +1101,16 @@ static void pmcr_write(CPUARMState *env, const
ARMCPRegInfo *ri,
env->cp15.c9_pmcr &= ~0x39;
env->cp15.c9_pmcr |= (value & 0x39);
- pmccntr_sync(env);
+ pmccntr_op_finish(env);
}
static uint64_t pmccntr_read(CPUARMState *env, const ARMCPRegInfo *ri)
{
- uint64_t total_ticks;
-
- if (!arm_ccnt_enabled(env)) {
- /* Counter is disabled, do not change value */
- return env->cp15.c15_ccnt;
- }
-
- total_ticks = muldiv64(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL),
- ARM_CPU_FREQ, NANOSECONDS_PER_SECOND);
-
- if (env->cp15.c9_pmcr & PMCRD) {
- /* Increment once every 64 processor clock cycles */
- total_ticks /= 64;
- }
- return total_ticks - env->cp15.c15_ccnt;
+ uint64_t ret;
+ pmccntr_op_start(env);
+ ret = env->cp15.c15_ccnt;
+ pmccntr_op_finish(env);
+ return ret;
}
static void pmselr_write(CPUARMState *env, const ARMCPRegInfo *ri,
@@ -1112,22 +1127,9 @@ static void pmselr_write(CPUARMState *env, const
ARMCPRegInfo *ri,
static void pmccntr_write(CPUARMState *env, const ARMCPRegInfo *ri,
uint64_t value)
{
- uint64_t total_ticks;
-
- if (!arm_ccnt_enabled(env)) {
- /* Counter is disabled, set the absolute value */
- env->cp15.c15_ccnt = value;
- return;
- }
-
- total_ticks = muldiv64(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL),
- ARM_CPU_FREQ, NANOSECONDS_PER_SECOND);
-
- if (env->cp15.c9_pmcr & PMCRD) {
- /* Increment once every 64 processor clock cycles */
- total_ticks /= 64;
- }
- env->cp15.c15_ccnt = total_ticks - value;
+ pmccntr_op_start(env);
+ env->cp15.c15_ccnt = value;
+ pmccntr_op_finish(env);
}
static void pmccntr_write32(CPUARMState *env, const ARMCPRegInfo *ri,
@@ -1140,7 +1142,11 @@ static void pmccntr_write32(CPUARMState *env, const
ARMCPRegInfo *ri,
#else /* CONFIG_USER_ONLY */
-void pmccntr_sync(CPUARMState *env)
+void pmccntr_op_start(CPUARMState *env)
+{
+}
+
+void pmccntr_op_finish(CPUARMState *env)
{
}
@@ -1149,9 +1155,9 @@ void pmccntr_sync(CPUARMState *env)
static void pmccfiltr_write(CPUARMState *env, const ARMCPRegInfo *ri,
uint64_t value)
{
- pmccntr_sync(env);
+ pmccntr_op_start(env);
env->cp15.pmccfiltr_el0 = value & 0xfc000000;
- pmccntr_sync(env);
+ pmccntr_op_finish(env);
}
static void pmcntenset_write(CPUARMState *env, const ARMCPRegInfo *ri,
--
Qualcomm Datacenter Technologies as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.
- [Qemu-devel] [PATCH v5 00/13] More fully implement ARM PMUv3, Aaron Lindsay, 2018/06/22
- [Qemu-devel] [PATCH v5 03/13] target/arm: Allow AArch32 access for PMCCFILTR, Aaron Lindsay, 2018/06/22
- [Qemu-devel] [PATCH v5 01/13] target/arm: Reorganize PMCCNTR accesses,
Aaron Lindsay <=
- [Qemu-devel] [PATCH v5 02/13] target/arm: Filter cycle counter based on PMCCFILTR_EL0, Aaron Lindsay, 2018/06/22
- [Qemu-devel] [PATCH v5 05/13] target/arm: Remove redundant DIV detection for KVM, Aaron Lindsay, 2018/06/22
- [Qemu-devel] [PATCH v5 06/13] target/arm: Implement PMOVSSET, Aaron Lindsay, 2018/06/22
- [Qemu-devel] [PATCH v5 04/13] target/arm: Add ARM_FEATURE_V7VE for v7 Virtualization Extensions, Aaron Lindsay, 2018/06/22
- [Qemu-devel] [PATCH v5 09/13] target/arm: PMU: Add instruction and cycle events, Aaron Lindsay, 2018/06/22
- [Qemu-devel] [PATCH v5 08/13] target/arm: Finish implementation of PM[X]EVCNTR and PM[X]EVTYPER, Aaron Lindsay, 2018/06/22