hv_exc: Avoid delivering spurious HV-triggered IPIs to the guest

Signed-off-by: Hector Martin <marcan@marcan.st>

src/hv.c

@@ -215,6 +215,10 @@ void hv_rendezvous(void)
 
 void hv_switch_cpu(int cpu)
 {
+    if (cpu > MAX_CPUS || cpu < 0 || !hv_started_cpus[cpu]) {
+        printf("HV: CPU #%d is inactive or invalid\n", cpu);
+        return;
+    }
     hv_rendezvous();
     printf("HV: switching to CPU #%d\n", cpu);
     hv_want_cpu = cpu;
@@ -297,6 +301,22 @@ void hv_rearm(void)
     msr(CNTP_CTL_EL0, CNTx_CTL_ENABLE);
 }
 
+void hv_check_rendezvous(u64 *regs)
+{
+    if (hv_want_cpu == smp_id()) {
+        hv_want_cpu = -1;
+        hv_exc_proxy(regs, START_HV, HV_USER_INTERRUPT, NULL);
+    } else if (hv_want_cpu != -1) {
+        // Unlock the HV so the target CPU can get into the proxy
+        spin_unlock(&bhl);
+        while (hv_want_cpu != -1)
+            sysop("dmb sy");
+        spin_lock(&bhl);
+        // Make sure we tick at least once more before running the guest
+        hv_rearm();
+    }
+}
+
 void hv_tick(u64 *regs)
 {
     if (hv_should_exit) {
@@ -305,8 +325,7 @@ void hv_tick(u64 *regs)
     }
     hv_wdt_pet();
     iodev_handle_events(uartproxy_iodev);
-    if (hv_want_cpu == smp_id() || iodev_can_read(uartproxy_iodev)) {
+    if (iodev_can_read(uartproxy_iodev)) {
-        hv_want_cpu = -1;
         hv_exc_proxy(regs, START_HV, HV_USER_INTERRUPT, NULL);
     }
     hv_vuart_poll();

src/hv.h

@@ -94,6 +94,7 @@ void hv_rendezvous(void);
 void hv_switch_cpu(int cpu);
 void hv_arm_tick(void);
 void hv_rearm(void);
+void hv_check_rendezvous(u64 *regs);
 void hv_tick(u64 *regs);
 
 #endif

src/hv_exc.c

@@ -22,6 +22,7 @@ extern spinlock_t bhl;
 #define D_PERCPU(t, x) t x[MAX_CPUS]
 #define PERCPU(x)      x[mrs(TPIDR_EL2)]
 
+D_PERCPU(static bool, ipi_queued);
 D_PERCPU(static bool, ipi_pending);
 D_PERCPU(static bool, pmc_pending);
 D_PERCPU(static u64, pmc_irq_mode);
@@ -184,9 +185,25 @@ static bool hv_handle_msr(u64 *regs, u64 iss)
          * don't do any wfis that assume otherwise in m1n1. */
         SYSREG_PASS(SYS_IMP_APL_CYC_OVRD)
         /* IPI handling */
-        SYSREG_PASS(SYS_IMP_APL_IPI_RR_LOCAL_EL1)
-        SYSREG_PASS(SYS_IMP_APL_IPI_RR_GLOBAL_EL1)
         SYSREG_PASS(SYS_IMP_APL_IPI_CR_EL1)
+        case SYSREG_ISS(SYS_IMP_APL_IPI_RR_LOCAL_EL1): {
+            assert(!is_read);
+            u64 mpidr = (regs[rt] & 0xff) | (mrs(MPIDR_EL1) & 0xffff00);
+            msr(SYS_IMP_APL_IPI_RR_LOCAL_EL1, regs[rt]);
+            for (int i = 0; i < MAX_CPUS; i++)
+                if (mpidr == smp_get_mpidr(i))
+                    ipi_queued[i] = true;
+            return true;
+        }
+        case SYSREG_ISS(SYS_IMP_APL_IPI_RR_GLOBAL_EL1):
+            assert(!is_read);
+            u64 mpidr = (regs[rt] & 0xff) | ((regs[rt] & 0xff0000) >> 8);
+            msr(SYS_IMP_APL_IPI_RR_LOCAL_EL1, regs[rt]);
+            for (int i = 0; i < MAX_CPUS; i++) {
+                if (mpidr == (smp_get_mpidr(i) & 0xffff))
+                    ipi_queued[i] = true;
+            }
+            return true;
         case SYSREG_ISS(SYS_IMP_APL_IPI_SR_EL1):
             if (is_read)
                 regs[rt] = PERCPU(ipi_pending) ? IPI_SR_PENDING : 0;
@@ -332,11 +349,14 @@ void hv_exc_fiq(u64 *regs)
     }
 
     if (mrs(SYS_IMP_APL_IPI_SR_EL1) & IPI_SR_PENDING) {
-        hv_tick(regs);
+        if (PERCPU(ipi_queued)) {
-        PERCPU(ipi_pending) = true;
+            PERCPU(ipi_pending) = true;
+            PERCPU(ipi_queued) = false;
+        }
         msr(SYS_IMP_APL_IPI_SR_EL1, IPI_SR_PENDING);
         sysop("isb");
     }
+    hv_check_rendezvous(regs);
 
     // Handles guest timers
     hv_exc_exit(regs);

src/smp.c

@@ -168,7 +168,8 @@ void smp_start_secondaries(void)
 
 void smp_send_ipi(int cpu)
 {
-    msr(SYS_IMP_APL_IPI_RR_GLOBAL_EL1, spin_table[cpu].mpidr);
+    u64 mpidr = spin_table[cpu].mpidr;
+    msr(SYS_IMP_APL_IPI_RR_GLOBAL_EL1, (mpidr & 0xff) | ((mpidr & 0xff00) << 8));
 }
 
 void smp_call4(int cpu, void *func, u64 arg0, u64 arg1, u64 arg2, u64 arg3)
@@ -220,7 +221,7 @@ bool smp_is_alive(int cpu)
     return spin_table[cpu].flag;
 }
 
-int smp_get_mpidr(int cpu)
+uint64_t smp_get_mpidr(int cpu)
 {
     return spin_table[cpu].mpidr;
 }

src/smp.h

@@ -25,7 +25,7 @@ void smp_call4(int cpu, void *func, u64 arg0, u64 arg1, u64 arg2, u64 arg3);
 u64 smp_wait(int cpu);
 
 bool smp_is_alive(int cpu);
-int smp_get_mpidr(int cpu);
+uint64_t smp_get_mpidr(int cpu);
 u64 smp_get_release_addr(int cpu);
 void smp_set_wfe_mode(bool new_mode);
 void smp_send_ipi(int cpu);