linux-kernel - Re: [PATCH v3 6/6] KVM: selftests: test KVM_GUESTDBG

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Date:   Tue, 07 Sep 2021 00:03:14 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org
Cc:     Kieran Bingham <kbingham@...nel.org>,
        Jan Kiszka <jan.kiszka@...mens.com>,
        Andrew Jones <drjones@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        Johannes Berg <johannes.berg@...el.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        "H. Peter Anvin" <hpa@...or.com>, Jessica Yu <jeyu@...nel.org>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Yang Weijiang <weijiang.yang@...el.com>,
        linux-kernel@...r.kernel.org, Borislav Petkov <bp@...en8.de>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        Shuah Khan <shuah@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v3 6/6] KVM: selftests: test KVM_GUESTDBG_BLOCKIRQ

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@...hat.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@...rship ~/Kernel/master/src/tools/testing/selftests/kvm]$./x86_64/debug_regs 
[mlevitsk@...rship ~/Kernel/master/src/tools/testing/selftests/kvm]$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);
> >