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

Maxim Levitsky
2021-09-06T21:03:32Z

On Mon, 2021-09-06 at 13:20 +0200, Paolo Bonzini wrote:
> 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.

Works for me :-(

[mlevitsk@starship ~/Kernel/master/src/tools/testing/selftests/kvm]$./x86_64/debug_regs
[mlevitsk@starship ~/Kernel/master/src/tools/testing/selftests/kvm]$echo $?
0

Maybe you run the test on kernel that doesn't support KVM_GUESTDBG_BLOCKIRQ?

Best regards,
Maxim Levitsky

>
> 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);
> >