Hmm... this is seeming a bit like whack-a-mole. Could we instead use
one of the valgrind hinting mechanisms to inform it that
kvm_get_one_reg() writes the variable at *target?
I didn't find a way of doing that looking in the memcheck helpers
(https://valgrind.org/docs/manual/mc-manual.html section 4.7). That would be a
good way of solving this warning because we would put stuff inside a specific
function X and all callers of X would be covered by it.
What I did find instead is a memcheck macro called VALGRIND_MAKE_MEM_DEFINED
that
tells Valgrind that the var was initialized.
This patch would then be something as follows:
diff --git a/target/ppc/kvm.c b/target/ppc/kvm.c
index dc93b99189..b0e22fa283 100644
--- a/target/ppc/kvm.c
+++ b/target/ppc/kvm.c
@@ -56,6 +56,10 @@
#define DEBUG_RETURN_GUEST 0
#define DEBUG_RETURN_GDB 1
+#ifdef CONFIG_VALGRIND_H
+#include <valgrind/memcheck.h>
+#endif
+
const KVMCapabilityInfo kvm_arch_required_capabilities[] = {
KVM_CAP_LAST_INFO
};
@@ -2539,6 +2543,10 @@ int kvmppc_enable_cap_large_decr(PowerPCCPU *cpu, int
enable)
CPUState *cs = CPU(cpu);
uint64_t lpcr;
+#ifdef CONFIG_VALGRIND_H
+ VALGRIND_MAKE_MEM_DEFINED(lpcr, sizeof(uint64_t));
+#endif
+
kvm_get_one_reg(cs, KVM_REG_PPC_LPCR_64, &lpcr);
/* Do we need to modify the LPCR? */
CONFIG_VALGRIND_H needs 'valgrind-devel´ installed.
I agree that this "Valgrind is complaining about variable initialization" is a
whack-a-mole
situation that will keep happening in the future if we keep adding this same
code pattern
(passing as reference an uninitialized var). For now, given that we have only 4
instances
to fix it in ppc code (as far as I'm aware of), and we don't have a better way
of telling
Valgrind that we know what we're doing, I think we're better of initializing
these vars.