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

From: Xiaoyao Li <xiaoyao.li@intel.com>
To: Sean Christopherson <seanjc@google.com>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>,
	Andy Lutomirski <luto@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Jim Mattson <jmattson@google.com>,
	David Rientjes <rientjes@google.com>,
	"Edgecombe, Rick P" <rick.p.edgecombe@intel.com>,
	"Kleen, Andi" <andi.kleen@intel.com>,
	"Yamahata, Isaku" <isaku.yamahata@intel.com>,
	Erdem Aktas <erdemaktas@google.com>,
	Steve Rutherford <srutherford@google.com>,
	Peter Gonda <pgonda@google.com>,
	David Hildenbrand <david@redhat.com>,
	x86@kernel.org, kvm@vger.kernel.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [RFCv2 13/13] KVM: unmap guest memory using poisoned pages
Date: Mon, 19 Apr 2021 19:32:23 +0800	[thread overview]
Message-ID: <fbbc8a7f-a143-9c6a-907f-19e0280842de@intel.com> (raw)
In-Reply-To: <YHnJtvXdrZE+AfM3@google.com>

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?