From: Raghavendra Rao Ananta rananta@google.com

[ Upstream commit 9e2f6498efbbc880d7caa7935839e682b64fe5a6 ]

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 Signed-off-by: Sasha Levin sashal@kernel.org --- tools/testing/selftests/kvm/lib/aarch64/ucall.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/kvm/lib/aarch64/ucall.c b/tools/testing/selftests/kvm/lib/aarch64/ucall.c index 2f37b90ee1a9..f600311fdc6a 100644 --- a/tools/testing/selftests/kvm/lib/aarch64/ucall.c +++ b/tools/testing/selftests/kvm/lib/aarch64/ucall.c @@ -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)