This is a note to let you know that I've just added the patch titled selftests: KVM: Handle compiler optimizations in ucall to the 5.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: selftests-kvm-handle-compiler-optimizations-in-ucall.patch and it can be found in the queue-5.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit a0664d286c2ec7914483ead8a722ae41a4b4c06b Author: Raghavendra Rao Ananta <rananta@xxxxxxxxxx> Date: Wed Jun 15 18:57:06 2022 +0000 selftests: KVM: Handle compiler optimizations in ucall [ 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@xxxxxxxxxx> Suggested-by: Reiji Watanabe <reijiw@xxxxxxxxxx> Signed-off-by: Raghavendra Rao Ananta <rananta@xxxxxxxxxx> Message-Id: <20220615185706.1099208-1-rananta@xxxxxxxxxx> Reviewed-by: Andrew Jones <drjones@xxxxxxxxxx> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/tools/testing/selftests/kvm/lib/aarch64/ucall.c b/tools/testing/selftests/kvm/lib/aarch64/ucall.c index 6cd91970fbad..3b2a426070c4 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)