linux-kernel - Re: [PATCH v7 11/14] KVM: Register/unregister the guest private memory regions

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Message-ID: <36e671d2-6b95-8e4f-c2ac-fee4b2670c6e@amd.com>
Date:   Tue, 19 Jul 2022 16:23:52 +0200
From:   "Gupta, Pankaj" <pankaj.gupta@....com>
To:     Chao Peng <chao.p.peng@...ux.intel.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
        linux-api@...r.kernel.org, linux-doc@...r.kernel.org,
        qemu-devel@...gnu.org, linux-kselftest@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        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>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H . Peter Anvin" <hpa@...or.com>,
        Hugh Dickins <hughd@...gle.com>,
        Jeff Layton <jlayton@...nel.org>,
        "J . Bruce Fields" <bfields@...ldses.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Shuah Khan <shuah@...nel.org>, Mike Rapoport <rppt@...nel.org>,
        Steven Price <steven.price@....com>,
        "Maciej S . Szmigiero" <mail@...iej.szmigiero.name>,
        Vlastimil Babka <vbabka@...e.cz>,
        Vishal Annapurve <vannapurve@...gle.com>,
        Yu Zhang <yu.c.zhang@...ux.intel.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        luto@...nel.org, jun.nakajima@...el.com, dave.hansen@...el.com,
        ak@...ux.intel.com, david@...hat.com, aarcange@...hat.com,
        ddutile@...hat.com, dhildenb@...hat.com,
        Quentin Perret <qperret@...gle.com>,
        Michael Roth <michael.roth@....com>, mhocko@...e.com,
        Muchun Song <songmuchun@...edance.com>
Subject: Re: [PATCH v7 11/14] KVM: Register/unregister the guest private
 memory regions


>>> +bool __weak kvm_arch_private_mem_supported(struct kvm *kvm)
>>> +{
>>> +	return false;
>>> +}
>>
>> Does this function has to be overriden by SEV and TDX to support the private
>> regions?
> 
> Yes it should be overridden by architectures which want to support it.

o.k
> 
>>
>>> +
>>>    static int check_memory_region_flags(const struct kvm_user_mem_region *mem)
>>>    {
>>>    	u32 valid_flags = KVM_MEM_LOG_DIRTY_PAGES;
>>> @@ -4689,6 +4729,22 @@ static long kvm_vm_ioctl(struct file *filp,
>>>    		r = kvm_vm_ioctl_set_memory_region(kvm, &mem);
>>>    		break;
>>>    	}
>>> +#ifdef CONFIG_HAVE_KVM_PRIVATE_MEM
>>> +	case KVM_MEMORY_ENCRYPT_REG_REGION:
>>> +	case KVM_MEMORY_ENCRYPT_UNREG_REGION: {
>>> +		struct kvm_enc_region region;
>>> +
>>> +		if (!kvm_arch_private_mem_supported(kvm))
>>> +			goto arch_vm_ioctl;
>>> +
>>> +		r = -EFAULT;
>>> +		if (copy_from_user(&region, argp, sizeof(region)))
>>> +			goto out;
>>> +
>>> +		r = kvm_vm_ioctl_set_encrypted_region(kvm, ioctl, &region);
>>
>> this is to store private region metadata not only the encrypted region?
> 
> Correct.

Sorry for not being clear, was suggesting name change of this function from:
"kvm_vm_ioctl_set_encrypted_region" to "kvm_vm_ioctl_set_private_region"

> 
>>
>> Also, seems same ioctl can be used to put other regions (e.g firmware, later
>> maybe DAX backend etc) into private memory?
> 
> Possibly. Depends on what exactly the semantics is. If just want to set
> those regions as private current code already support that.

Agree. Sure!


Thanks,
Pankaj