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

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Date:   Mon, 6 Sep 2021 13:20:14 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Maxim Levitsky <mlevitsk@...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 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.

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);
>