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selftests: KVM: Handle compiler optimizations in ucall

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The selftests, when built with newer versions of clang, is found
to have over optimized guests' ucall() function, and eliminating
the stores for uc.cmd (perhaps due to no immediate readers). This
resulted in the userspace side always reading a value of '0', and
causing multiple test failures.

As a result, prevent the compiler from optimizing the stores in
ucall() with WRITE_ONCE().

Suggested-by: Ricardo Koller <ricarkol@google.com>
Suggested-by: Reiji Watanabe <reijiw@google.com>
Signed-off-by: Raghavendra Rao Ananta <rananta@google.com>
Message-Id: <20220615185706.1099208-1-rananta@google.com>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Raghavendra Rao Ananta 2022-06-15 18:57:06 +00:00 committed by Paolo Bonzini
parent 933b5f9f98
commit 9e2f6498ef
1 changed files with 4 additions and 5 deletions
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9
tools/testing/selftests/kvm/lib/aarch64/ucall.c
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@ -73,20 +73,19 @@ void ucall_uninit(struct kvm_vm *vm)
void ucall(uint64_t cmd, int nargs, ...)
{
struct ucall uc = {
.cmd = cmd,
};
struct ucall uc = {};
va_list va;
int i;
WRITE_ONCE(uc.cmd, cmd);
nargs = nargs <= UCALL_MAX_ARGS ? nargs : UCALL_MAX_ARGS;
va_start(va, nargs);
for (i = 0; i < nargs; ++i)
uc.args[i] = va_arg(va, uint64_t);
WRITE_ONCE(uc.args[i], va_arg(va, uint64_t));
va_end(va);
*ucall_exit_mmio_addr = (vm_vaddr_t)&uc;
WRITE_ONCE(*ucall_exit_mmio_addr, (vm_vaddr_t)&uc);
}
uint64_t get_ucall(struct kvm_vm *vm, uint32_t vcpu_id, struct ucall *uc)