Automatically disable single-step when the guest reaches the end of the verified section instead of using an explicit ucall() to ask userspace to disable single-step. An upcoming change to implement a pool-based scheme for ucall() will add an atomic operation (bit test and set) in the guest ucall code, and if the compiler generate "old school" atomics, e.g.
40e57c: c85f7c20 ldxr x0, [x1] 40e580: aa100011 orr x17, x0, x16 40e584: c80ffc31 stlxr w15, x17, [x1] 40e588: 35ffffaf cbnz w15, 40e57c <__aarch64_ldset8_sync+0x1c> the guest will hang as the local exclusive monitor is reset by eret, i.e. the stlxr will always fail due to the VM-Exit for the debug exception. Link: https://lore.kernel.org/all/20221006003409.649993-8-sea...@google.com Cc: Oliver Upton <oliver.up...@linux.dev> Cc: Marc Zyngier <m...@kernel.org> Signed-off-by: Sean Christopherson <sea...@google.com> --- .../selftests/kvm/aarch64/debug-exceptions.c | 28 ++++++++++--------- 1 file changed, 15 insertions(+), 13 deletions(-) diff --git a/tools/testing/selftests/kvm/aarch64/debug-exceptions.c b/tools/testing/selftests/kvm/aarch64/debug-exceptions.c index 91f55b45dfc7..65cd7e4f07fa 100644 --- a/tools/testing/selftests/kvm/aarch64/debug-exceptions.c +++ b/tools/testing/selftests/kvm/aarch64/debug-exceptions.c @@ -241,7 +241,6 @@ static void guest_svc_handler(struct ex_regs *regs) enum single_step_op { SINGLE_STEP_ENABLE = 0, - SINGLE_STEP_DISABLE = 1, }; static void guest_code_ss(int test_cnt) @@ -258,7 +257,7 @@ static void guest_code_ss(int test_cnt) GUEST_SYNC(SINGLE_STEP_ENABLE); /* - * The userspace will veriry that the pc is as expected during + * The userspace will verify that the pc is as expected during * single step execution between iter_ss_begin and iter_ss_end. */ asm volatile("iter_ss_begin:nop\n"); @@ -268,11 +267,9 @@ static void guest_code_ss(int test_cnt) bvr = read_sysreg(dbgbvr0_el1); wvr = read_sysreg(dbgwvr0_el1); + /* Userspace disables Single Step when the end is nigh. */ asm volatile("iter_ss_end:\n"); - /* Disable Single Step execution */ - GUEST_SYNC(SINGLE_STEP_DISABLE); - GUEST_ASSERT(bvr == w_bvr); GUEST_ASSERT(wvr == w_wvr); } @@ -364,15 +361,12 @@ void test_single_step_from_userspace(int test_cnt) TEST_ASSERT(cmd == UCALL_SYNC, "Unexpected ucall cmd 0x%lx", cmd); - if (uc.args[1] == SINGLE_STEP_ENABLE) { - debug.control = KVM_GUESTDBG_ENABLE | - KVM_GUESTDBG_SINGLESTEP; - ss_enable = true; - } else { - debug.control = KVM_GUESTDBG_ENABLE; - ss_enable = false; - } + TEST_ASSERT(uc.args[1] == SINGLE_STEP_ENABLE, + "Unexpected ucall action 0x%lx", uc.args[1]); + debug.control = KVM_GUESTDBG_ENABLE | + KVM_GUESTDBG_SINGLESTEP; + ss_enable = true; vcpu_guest_debug_set(vcpu, &debug); continue; } @@ -385,6 +379,14 @@ void test_single_step_from_userspace(int test_cnt) "Unexpected pc 0x%lx (expected 0x%lx)", pc, test_pc); + if ((pc + 4) == (uint64_t)&iter_ss_end) { + test_pc = 0; + debug.control = KVM_GUESTDBG_ENABLE; + ss_enable = false; + vcpu_guest_debug_set(vcpu, &debug); + continue; + } + /* * If the current pc is between iter_ss_bgin and * iter_ss_end, the pc for the next KVM_EXIT_DEBUG should -- 2.38.1.431.g37b22c650d-goog _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
