linux-kernel - Re: [PATCH] KVM: selftests: page_table_test: fix calculation of guest_test_phys

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Date:   Fri, 26 Nov 2021 17:11:08 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     "Maciej S. Szmigiero" <mail@...iej.szmigiero.name>
Cc:     Shuah Khan <shuah@...nel.org>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Igor Mammedov <imammedo@...hat.com>,
        Yanan Wang <wangyanan55@...wei.com>,
        Andrew Jones <drjones@...hat.com>, kvm@...r.kernel.org,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: selftests: page_table_test: fix calculation of
 guest_test_phys_mem

On 11/26/21 16:28, Maciej S. Szmigiero wrote:
> From: "Maciej S. Szmigiero" <maciej.szmigiero@...cle.com>
> 
> A kvm_page_table_test run with its default settings fails on VMX due to
> memory region add failure:
>> ==== Test Assertion Failure ====
>>   lib/kvm_util.c:952: ret == 0
>>   pid=10538 tid=10538 errno=17 - File exists
>>      1  0x00000000004057d1: vm_userspace_mem_region_add at kvm_util.c:947
>>      2  0x0000000000401ee9: pre_init_before_test at kvm_page_table_test.c:302
>>      3   (inlined by) run_test at kvm_page_table_test.c:374
>>      4  0x0000000000409754: for_each_guest_mode at guest_modes.c:53
>>      5  0x0000000000401860: main at kvm_page_table_test.c:500
>>      6  0x00007f82ae2d8554: ?? ??:0
>>      7  0x0000000000401894: _start at ??:?
>>   KVM_SET_USER_MEMORY_REGION IOCTL failed,
>>   rc: -1 errno: 17
>>   slot: 1 flags: 0x0
>>   guest_phys_addr: 0xc0000000 size: 0x40000000
> 
> This is because the memory range that this test is trying to add
> (0x0c0000000 - 0x100000000) conflicts with LAPIC mapping at 0x0fee00000.
> 
> Looking at the code it seems that guest_test_*phys*_mem variable gets
> mistakenly overwritten with guest_test_*virt*_mem while trying to adjust
> the former for alignment.
> With the correct variable adjusted this test runs successfully.
> 
> Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@...cle.com>
> ---
>   tools/testing/selftests/kvm/kvm_page_table_test.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/kvm/kvm_page_table_test.c b/tools/testing/selftests/kvm/kvm_page_table_test.c
> index 3836322add00..ba1fdc3dcf4a 100644
> --- a/tools/testing/selftests/kvm/kvm_page_table_test.c
> +++ b/tools/testing/selftests/kvm/kvm_page_table_test.c
> @@ -280,7 +280,7 @@ static struct kvm_vm *pre_init_before_test(enum vm_guest_mode mode, void *arg)
>   #ifdef __s390x__
>   	alignment = max(0x100000, alignment);
>   #endif
> -	guest_test_phys_mem = align_down(guest_test_virt_mem, alignment);
> +	guest_test_phys_mem = align_down(guest_test_phys_mem, alignment);
>   
>   	/* Set up the shared data structure test_args */
>   	test_args.vm = vm;
> 

Queued, thanks.

Paolo