Re: [PATCH v3 6/6] KVM: selftests: test KVM_GUESTDBG_BLOCKIRQ

Vitaly Kuznetsov
2021-11-01T15:43:34Z

Paolo Bonzini <pbonzini@redhat.com> writes:

> On 11/08/21 14:29, Maxim Levitsky wrote:
>> Modify debug_regs test to create a pending interrupt
>> and see that it is blocked when single stepping is done
>> with KVM_GUESTDBG_BLOCKIRQ
>>
>> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
>> ---
>> .../testing/selftests/kvm/x86_64/debug_regs.c | 24 ++++++++++++++++---
>> 1 file changed, 21 insertions(+), 3 deletions(-)
>
> I haven't looked very much at this, but the test fails.
>

Same here,

the test passes on AMD but fails consistently on Intel:

# ./x86_64/debug_regs
==== Test Assertion Failure ====
x86_64/debug_regs.c:179: run->exit_reason == KVM_EXIT_DEBUG && run->debug.arch.exception == DB_VECTOR && run->debug.arch.pc == target_rip && run->debug.arch.dr6 == target_dr6
pid=13434 tid=13434 errno=0 - Success
1 0x00000000004027c6: main at debug_regs.c:179
2 0x00007f65344cf554: ?? ??:0
3 0x000000000040294a: _start at ??:?
SINGLE_STEP[1]: exit 8 exception 1 rip 0x402a25 (should be 0x402a27) dr6 0xffff4ff0 (should be 0xffff4ff0)

(I know I'm late to the party).

> Paolo
>
>> diff --git a/tools/testing/selftests/kvm/x86_64/debug_regs.c b/tools/testing/selftests/kvm/x86_64/debug_regs.c
>> index 6097a8283377..5f078db1bcba 100644
>> --- a/tools/testing/selftests/kvm/x86_64/debug_regs.c
>> +++ b/tools/testing/selftests/kvm/x86_64/debug_regs.c
>> @@ -8,12 +8,15 @@
>> #include <string.h>
>> #include "kvm_util.h"
>> #include "processor.h"
>> +#include "apic.h"
>>
>> #define VCPU_ID 0
>>
>> #define DR6_BD (1 << 13)
>> #define DR7_GD (1 << 13)
>>
>> +#define IRQ_VECTOR 0xAA
>> +
>> /* For testing data access debug BP */
>> uint32_t guest_value;
>>
>> @@ -21,6 +24,11 @@ extern unsigned char sw_bp, hw_bp, write_data, ss_start, bd_start;
>>
>> static void guest_code(void)
>> {
>> + /* Create a pending interrupt on current vCPU */
>> + x2apic_enable();
>> + x2apic_write_reg(APIC_ICR, APIC_DEST_SELF | APIC_INT_ASSERT |
>> + APIC_DM_FIXED | IRQ_VECTOR);
>> +
>> /*
>> * Software BP tests.
>> *
>> @@ -38,12 +46,19 @@ static void guest_code(void)
>> "mov %%rax,%0;\n\t write_data:"
>> : "=m" (guest_value) : : "rax");
>>
>> - /* Single step test, covers 2 basic instructions and 2 emulated */
>> + /*
>> + * Single step test, covers 2 basic instructions and 2 emulated
>> + *
>> + * Enable interrupts during the single stepping to see that
>> + * pending interrupt we raised is not handled due to KVM_GUESTDBG_BLOCKIRQ
>> + */
>> asm volatile("ss_start: "
>> + "sti\n\t"
>> "xor %%eax,%%eax\n\t"
>> "cpuid\n\t"
>> "movl $0x1a0,%%ecx\n\t"
>> "rdmsr\n\t"
>> + "cli\n\t"
>> : : : "eax", "ebx", "ecx", "edx");
>>
>> /* DR6.BD test */
>> @@ -72,11 +87,13 @@ int main(void)
>> uint64_t cmd;
>> int i;
>> /* Instruction lengths starting at ss_start */
>> - int ss_size[4] = {
>> + int ss_size[6] = {
>> + 1, /* sti*/
>> 2, /* xor */
>> 2, /* cpuid */
>> 5, /* mov */
>> 2, /* rdmsr */
>> + 1, /* cli */
>> };
>>
>> if (!kvm_check_cap(KVM_CAP_SET_GUEST_DEBUG)) {
>> @@ -154,7 +171,8 @@ int main(void)
>> for (i = 0; i < (sizeof(ss_size) / sizeof(ss_size[0])); i++) {
>> target_rip += ss_size[i];
>> CLEAR_DEBUG();
>> - debug.control = KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_SINGLESTEP;
>> + debug.control = KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_SINGLESTEP |
>> + KVM_GUESTDBG_BLOCKIRQ;
>> debug.arch.debugreg[7] = 0x00000400;
>> APPLY_DEBUG();
>> vcpu_run(vm, VCPU_ID);
>>
>

--
Vitaly