linux-kernel - Re: [RFCv2 13/13] KVM: unmap guest memory using poisoned pages

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Date:   Mon, 19 Apr 2021 19:32:23 +0800
From:   Xiaoyao Li <xiaoyao.li@...el.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Jim Mattson <jmattson@...gle.com>,
        David Rientjes <rientjes@...gle.com>,
        "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
        "Kleen, Andi" <andi.kleen@...el.com>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>,
        Erdem Aktas <erdemaktas@...gle.com>,
        Steve Rutherford <srutherford@...gle.com>,
        Peter Gonda <pgonda@...gle.com>,
        David Hildenbrand <david@...hat.com>, x86@...nel.org,
        kvm@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFCv2 13/13] KVM: unmap guest memory using poisoned pages

On 4/17/2021 1:30 AM, Sean Christopherson wrote:
> On Fri, Apr 16, 2021, Kirill A. Shutemov wrote:
[...]
>> index fadaccb95a4c..cd2374802702 100644
>> --- a/include/linux/kvm_host.h
>> +++ b/include/linux/kvm_host.h
>> @@ -436,6 +436,8 @@ static inline int kvm_arch_vcpu_memslots_id(struct kvm_vcpu *vcpu)
>>   }
>>   #endif
>>   
>> +#define KVM_NR_SHARED_RANGES 32
>> +
>>   /*
>>    * Note:
>>    * memslots are not sorted by id anymore, please use id_to_memslot()
>> @@ -513,6 +515,10 @@ struct kvm {
>>   	pid_t userspace_pid;
>>   	unsigned int max_halt_poll_ns;
>>   	u32 dirty_ring_size;
>> +	bool mem_protected;
>> +	void *id;
>> +	int nr_shared_ranges;
>> +	struct range shared_ranges[KVM_NR_SHARED_RANGES];
> 
> Hard no for me.  IMO, anything that requires KVM to track shared/pinned pages in
> a separate tree/array is non-starter.  More specific to TDX #MCs, KVM should not
> be the canonical reference for the state of a page.
> 

Do you mean something in struct page to track if the page is shared or 
private?