From 10e7a099bfd860a2b77ea8aaac661f52c16dd865 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Mon, 25 Oct 2021 13:13:11 -0700 Subject: selftests: KVM: Add test to verify KVM doesn't explode on "bad" I/O Add an x86 selftest to verify that KVM doesn't WARN or otherwise explode if userspace modifies RCX during a userspace exit to handle string I/O. This is a regression test for a user-triggerable WARN introduced by commit 3b27de271839 ("KVM: x86: split the two parts of emulator_pio_in"). Signed-off-by: Sean Christopherson Message-Id: <20211025201311.1881846-3-seanjc@google.com> Signed-off-by: Paolo Bonzini --- tools/testing/selftests/kvm/.gitignore | 1 + tools/testing/selftests/kvm/Makefile | 1 + .../selftests/kvm/x86_64/userspace_io_test.c | 114 +++++++++++++++++++++ 3 files changed, 116 insertions(+) create mode 100644 tools/testing/selftests/kvm/x86_64/userspace_io_test.c (limited to 'tools/testing') diff --git a/tools/testing/selftests/kvm/.gitignore b/tools/testing/selftests/kvm/.gitignore index 3763105029fb..00814c0f87a6 100644 --- a/tools/testing/selftests/kvm/.gitignore +++ b/tools/testing/selftests/kvm/.gitignore @@ -30,6 +30,7 @@ /x86_64/svm_int_ctl_test /x86_64/sync_regs_test /x86_64/tsc_msrs_test +/x86_64/userspace_io_test /x86_64/userspace_msr_exit_test /x86_64/vmx_apic_access_test /x86_64/vmx_close_while_nested_test diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile index c4e34717826a..f307c9f61981 100644 --- a/tools/testing/selftests/kvm/Makefile +++ b/tools/testing/selftests/kvm/Makefile @@ -59,6 +59,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/vmx_preemption_timer_test TEST_GEN_PROGS_x86_64 += x86_64/svm_vmcall_test TEST_GEN_PROGS_x86_64 += x86_64/svm_int_ctl_test TEST_GEN_PROGS_x86_64 += x86_64/sync_regs_test +TEST_GEN_PROGS_x86_64 += x86_64/userspace_io_test TEST_GEN_PROGS_x86_64 += x86_64/userspace_msr_exit_test TEST_GEN_PROGS_x86_64 += x86_64/vmx_apic_access_test TEST_GEN_PROGS_x86_64 += x86_64/vmx_close_while_nested_test diff --git a/tools/testing/selftests/kvm/x86_64/userspace_io_test.c b/tools/testing/selftests/kvm/x86_64/userspace_io_test.c new file mode 100644 index 000000000000..e4bef2e05686 --- /dev/null +++ b/tools/testing/selftests/kvm/x86_64/userspace_io_test.c @@ -0,0 +1,114 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include +#include + +#include "test_util.h" + +#include "kvm_util.h" +#include "processor.h" + +#define VCPU_ID 1 + +static void guest_ins_port80(uint8_t *buffer, unsigned int count) +{ + unsigned long end; + + if (count == 2) + end = (unsigned long)buffer + 1; + else + end = (unsigned long)buffer + 8192; + + asm volatile("cld; rep; insb" : "+D"(buffer), "+c"(count) : "d"(0x80) : "memory"); + GUEST_ASSERT_1(count == 0, count); + GUEST_ASSERT_2((unsigned long)buffer == end, buffer, end); +} + +static void guest_code(void) +{ + uint8_t buffer[8192]; + int i; + + /* + * Special case tests. main() will adjust RCX 2 => 1 and 3 => 8192 to + * test that KVM doesn't explode when userspace modifies the "count" on + * a userspace I/O exit. KVM isn't required to play nice with the I/O + * itself as KVM doesn't support manipulating the count, it just needs + * to not explode or overflow a buffer. + */ + guest_ins_port80(buffer, 2); + guest_ins_port80(buffer, 3); + + /* Verify KVM fills the buffer correctly when not stuffing RCX. */ + memset(buffer, 0, sizeof(buffer)); + guest_ins_port80(buffer, 8192); + for (i = 0; i < 8192; i++) + GUEST_ASSERT_2(buffer[i] == 0xaa, i, buffer[i]); + + GUEST_DONE(); +} + +int main(int argc, char *argv[]) +{ + struct kvm_regs regs; + struct kvm_run *run; + struct kvm_vm *vm; + struct ucall uc; + int rc; + + /* Tell stdout not to buffer its content */ + setbuf(stdout, NULL); + + /* Create VM */ + vm = vm_create_default(VCPU_ID, 0, guest_code); + run = vcpu_state(vm, VCPU_ID); + + memset(®s, 0, sizeof(regs)); + + while (1) { + rc = _vcpu_run(vm, VCPU_ID); + + TEST_ASSERT(rc == 0, "vcpu_run failed: %d\n", rc); + TEST_ASSERT(run->exit_reason == KVM_EXIT_IO, + "Unexpected exit reason: %u (%s),\n", + run->exit_reason, + exit_reason_str(run->exit_reason)); + + if (get_ucall(vm, VCPU_ID, &uc)) + break; + + TEST_ASSERT(run->io.port == 0x80, + "Expected I/O at port 0x80, got port 0x%x\n", run->io.port); + + /* + * Modify the rep string count in RCX: 2 => 1 and 3 => 8192. + * Note, this abuses KVM's batching of rep string I/O to avoid + * getting stuck in an infinite loop. That behavior isn't in + * scope from a testing perspective as it's not ABI in any way, + * i.e. it really is abusing internal KVM knowledge. + */ + vcpu_regs_get(vm, VCPU_ID, ®s); + if (regs.rcx == 2) + regs.rcx = 1; + if (regs.rcx == 3) + regs.rcx = 8192; + memset((void *)run + run->io.data_offset, 0xaa, 4096); + vcpu_regs_set(vm, VCPU_ID, ®s); + } + + switch (uc.cmd) { + case UCALL_DONE: + break; + case UCALL_ABORT: + TEST_FAIL("%s at %s:%ld : argN+1 = 0x%lx, argN+2 = 0x%lx", + (const char *)uc.args[0], __FILE__, uc.args[1], + uc.args[2], uc.args[3]); + default: + TEST_FAIL("Unknown ucall %lu", uc.cmd); + } + + kvm_vm_free(vm); + return 0; +} -- cgit