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Subject: Re: Re: [PATCH v5 1/4] KVM: selftests: Add KVM selftests header files
 for LoongArch
To:     Sean Christopherson <seanjc@google.com>
Cc:     Shuah Khan <shuah@kernel.org>, Paolo Bonzini <pbonzini@redhat.com>,
        linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        Vishal Annapurve <vannapurve@google.com>,
        Huacai Chen <chenhuacai@kernel.org>,
        WANG Xuerui <kernel@xen0n.name>, loongarch@lists.linux.dev,
        Peter Xu <peterx@redhat.com>,
        Vipin Sharma <vipinsh@google.com>, maobibo@loongson.cn
References: <20231130111804.2227570-1-zhaotianrui@loongson.cn>
 <20231130111804.2227570-2-zhaotianrui@loongson.cn>
 <e40d3884-bf39-8286-627f-e0ce7dacfcbe@loongson.cn>
 <ZXiV1rMrXY0hNgvZ@google.com>
From:   zhaotianrui <zhaotianrui@loongson.cn>
Message-ID: <023b6f8f-301b-a6d0-448b-09a602ba1141@loongson.cn>
Date:   Wed, 13 Dec 2023 15:15:28 +0800
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在 2023/12/13 上午1:18, Sean Christopherson 写道:
> On Tue, Dec 12, 2023, zhaotianrui wrote:
>> Hi, Sean:
>>
>> I want to change the definition of  DEFAULT_GUEST_TEST_MEM in the common
>> file "memstress.h", like this:
>>
>>   /* Default guest test virtual memory offset */
>> +#ifndef DEFAULT_GUEST_TEST_MEM
>>   #define DEFAULT_GUEST_TEST_MEM		0xc0000000
>> +#endif
>>
>> As this address should be re-defined in LoongArch headers.
> 
> Why?  E.g. is 0xc0000000 unconditionally reserved, not guaranteed to be valid,
> something else?
> 
>> So, do you have any suggesstion?
> 
> Hmm, I think ideally kvm_util_base.h would define a range of memory that can be
> used by tests for arbitrary data.  Multiple tests use 0xc0000000, which is not
> entirely arbitrary, i.e. it doesn't _need_ to be 0xc0000000, but 0xc0000000 is
> convenient because it's 32-bit addressable and doesn't overlap reserved areas in
> other architectures.
> 
Thanks for your explanation, and LoongArch want to define 
DEFAULT_GUEST_TEST_MEM to 0x130000000. As default base address for 
application loading is 0x120000000, DEFAULT_GUEST_TEST_MEM should be 
larger than app loading address, so that PER_VCPU_MEM_SIZE can be large 
enough, and kvm selftests app size is smaller than 256M in generic.

Thanks
Tianrui Zhao