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Subject: Re: [PATCH v2] KVM: selftests: Compile code with warnings enabled
To:     Thomas Huth <thuth@redhat.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Peter Xu <peterx@redhat.com>
Cc:     =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= <rkrcmar@redhat.com>,
        linux-kselftest@vger.kernel.org, kvm@vger.kernel.org,
        Shuah Khan <shuah@kernel.org>,
        Andrew Jones <drjones@redhat.com>, linux-kernel@vger.kernel.org
References: <20190517090445.4502-1-thuth@redhat.com>
 <20190517093000.GO16681@xz-x1> <8736ldquyw.fsf@vitty.brq.redhat.com>
 <1834df0f-b377-2231-0e5c-c5acd3298973@redhat.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <505274ec-e73f-f362-8130-5f70673bfc80@redhat.com>
Date:   Mon, 20 May 2019 12:00:44 +0200
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On 17/05/19 12:07, Thomas Huth wrote:
> 
> lib/ucall.c: In function ‘get_ucall’:
> lib/ucall.c:145:3: warning: dereferencing type-punned pointer will break
> strict-aliasing rules [-Wstrict-aliasing]
>    gva = *(vm_vaddr_t *)run->mmio.data;
> 
> x86_64/vmx_set_nested_state_test.c: In function
> ‘set_revision_id_for_vmcs12’:
> x86_64/vmx_set_nested_state_test.c:78:2: warning: dereferencing
> type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
>   *(u32 *)(state->data) = vmcs12_revision;
> 
> ... how do we want to handle such spots in the kvm selftest code?
> Compile with -fno-strict-aliasing? Or fix it with type-punning through
> unions?

I would use memcpy.  I'll send a patch shortly.

Paolo