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From: Wei Huang <wei.huang2@amd.com>
To: Sean Christopherson <seanjc@google.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	pbonzini@redhat.com, vkuznets@redhat.com, wanpengli@tencent.com,
	jmattson@google.com, joro@8bytes.org, tglx@linutronix.de,
	mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com
Subject: Re: [PATCH v2 2/3] KVM: x86: Handle the case of 5-level shadow page table
Date: Mon, 9 Aug 2021 12:03:45 -0500	[thread overview]
Message-ID: <52fe9c7d-a97b-06cc-570a-ba2d83f26d7c@amd.com> (raw)
In-Reply-To: <YRFG+NDkjVK0myDn@google.com>



On 8/9/21 10:17 AM, Sean Christopherson wrote:
> On Sun, Aug 08, 2021, Wei Huang wrote:
>> @@ -3457,10 +3457,19 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
>>  		mmu->pae_root[i] = root | pm_mask;
>>  	}
>>  
>> -	if (mmu->shadow_root_level == PT64_ROOT_4LEVEL)
>> +	/*
>> +	 * Depending on the shadow_root_level, build the root_hpa table by
>> +	 * chaining either pml5->pml4->pae or pml4->pae.
>> +	 */
>> +	mmu->root_hpa = __pa(mmu->pae_root);
>> +	if (mmu->shadow_root_level >= PT64_ROOT_4LEVEL) {
>> +		mmu->pml4_root[0] = mmu->root_hpa | pm_mask;
>>  		mmu->root_hpa = __pa(mmu->pml4_root);
>> -	else
>> -		mmu->root_hpa = __pa(mmu->pae_root);
>> +	}
>> +	if (mmu->shadow_root_level == PT64_ROOT_5LEVEL) {
>> +		mmu->pml5_root[0] = mmu->root_hpa | pm_mask;
>> +		mmu->root_hpa = __pa(mmu->pml5_root);
>> +	}
> 
> I still really dislike this approach, it requires visually connecting multiple
> statements to understand the chain.  I don't see any advantage (the 6-level paging
> comment was 99.9% a joke) of rewriting root_hpa other than that's how it's done today.
> 

I can change this part in v3, unless different comments from other
reviewers.

> In the future, please give reviewers ample opportunity to respond before sending
> a new version if there's disagreement, otherwise the conversation gets carried
> over into a different thread and loses the original context.
> 
>>  
>>  set_root_pgd:
>>  	mmu->root_pgd = root_pgd;

  reply	other threads:[~2021-08-09 17:03 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-08 19:26 [PATCH v2 0/3] SVM 5-level page table support Wei Huang
2021-08-08 19:26 ` [PATCH v2 1/3] KVM: x86: Allow CPU to force vendor-specific TDP level Wei Huang
2021-08-09  3:58   ` Yu Zhang
2021-08-09  4:11     ` Wei Huang
2021-08-09  4:27       ` Yu Zhang
2021-08-09  4:33         ` Wei Huang
2021-08-09  6:42           ` Yu Zhang
2021-08-09 15:30             ` Sean Christopherson
2021-08-09 21:49               ` Jim Mattson
2021-08-10  9:23                 ` Paolo Bonzini
2021-08-10  7:40               ` Yu Zhang
2021-08-10  9:25                 ` Paolo Bonzini
2021-08-10 11:00                   ` Yu Zhang
2021-08-10 12:47                     ` Paolo Bonzini
2021-08-10 14:37                       ` Yu Zhang
2021-08-08 19:26 ` [PATCH v2 2/3] KVM: x86: Handle the case of 5-level shadow page table Wei Huang
2021-08-09 15:17   ` Sean Christopherson
2021-08-09 17:03     ` Wei Huang [this message]
2021-08-08 19:26 ` [PATCH v2 3/3] KVM: SVM: Add 5-level page table support for SVM Wei Huang

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