Commit b884af0f authored by Raghavendra Rao Ananta's avatar Raghavendra Rao Ananta Committed by Zheng Zengkai
Browse files

selftests: KVM: Handle compiler optimizations in ucall 

stable inclusion
from stable-v5.10.136
commit 50763f0ac0706e63c0ba550adccfca25eb3d0667
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5ZWNE

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=50763f0ac0706e63c0ba550adccfca25eb3d0667



--------------------------------

[ Upstream commit 9e2f6498 ]

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: default avatarRicardo Koller <ricarkol@google.com>
Suggested-by: default avatarReiji Watanabe <reijiw@google.com>
Signed-off-by: default avatarRaghavendra Rao Ananta <rananta@google.com>
Message-Id: <20220615185706.1099208-1-rananta@google.com>
Reviewed-by: default avatarAndrew Jones <drjones@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
Signed-off-by: default avatarZheng Zengkai <zhengzengkai@huawei.com>
Reviewed-by: default avatarWei Li <liwei391@huawei.com>
parent d70e25f2

tools/testing/selftests/kvm/lib/aarch64/ucall.c

+4 −5
Original line number Diff line number Diff line
@@ -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)