powerpc: Mark writes registering ipi to host cpu through kvm and polling

Mark writes to hypervisor ipi state so that KCSAN recognises these
asynchronous issue of kvmppc_{set,clear}_host_ipi to be intended, with
atomic writes. Mark asynchronous polls to this variable in
kvm_ppc_read_one_intr().

Signed-off-by: Rohan McLure <[email protected]>
Reviewed-by: Nicholas Piggin <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>
Link: https://msgid.link/[email protected]

Author: rohanmclure

arch/powerpc/include/asm/kvm_ppc.h

@@ -548,12 +548,12 @@ static inline void kvmppc_set_host_ipi(int cpu)
 	 * pairs with the barrier in kvmppc_clear_host_ipi()
 	 */
 	smp_mb();
-	paca_ptrs[cpu]->kvm_hstate.host_ipi = 1;
+	WRITE_ONCE(paca_ptrs[cpu]->kvm_hstate.host_ipi, 1);
 }
 
 static inline void kvmppc_clear_host_ipi(int cpu)
 {
-	paca_ptrs[cpu]->kvm_hstate.host_ipi = 0;
+	WRITE_ONCE(paca_ptrs[cpu]->kvm_hstate.host_ipi, 0);
 	/*
 	 * order clearing of host_ipi flag vs. processing of IPI messages
 	 *

arch/powerpc/kvm/book3s_hv_builtin.c

@@ -406,7 +406,7 @@ static long kvmppc_read_one_intr(bool *again)
 		return 1;
 
 	/* see if a host IPI is pending */
-	host_ipi = local_paca->kvm_hstate.host_ipi;
+	host_ipi = READ_ONCE(local_paca->kvm_hstate.host_ipi);
 	if (host_ipi)
 		return 1;
 
@@ -466,7 +466,7 @@ static long kvmppc_read_one_intr(bool *again)
 		 * meantime. If it's clear, we bounce the interrupt to the
 		 * guest
 		 */
-		host_ipi = local_paca->kvm_hstate.host_ipi;
+		host_ipi = READ_ONCE(local_paca->kvm_hstate.host_ipi);
 		if (unlikely(host_ipi != 0)) {
 			/* We raced with the host,
 			 * we need to resend that IPI, bummer