LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Paolo Bonzini <pbonzini@redhat.com>
To: Sean Christopherson <seanjc@google.com>, Wei Huang <wei.huang2@amd.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	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 v3 3/3] KVM: SVM: Add 5-level page table support for SVM
Date: Thu, 19 Aug 2021 18:38:57 +0200	[thread overview]
Message-ID: <d5894435-c5e1-890d-880c-6b6390fe50d8@redhat.com> (raw)
In-Reply-To: <YR1EPNRNtIZZ7LXd@google.com>

On 18/08/21 19:32, Sean Christopherson wrote:
> On Wed, Aug 18, 2021, Wei Huang wrote:
>> When the 5-level page table is enabled on host OS, the nested page table
>> for guest VMs must use 5-level as well. Update get_npt_level() function
>> to reflect this requirement. In the meanwhile, remove the code that
>> prevents kvm-amd driver from being loaded when 5-level page table is
>> detected.
>>
>> Signed-off-by: Wei Huang <wei.huang2@amd.com>
>> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> 
> If this patch authored by Paolo, he needs to be attributed via From:.  If Paolo
> is a co-author, he needs a Co-developed-by:.  If either of those is true, your
> SOB needs to be last in the chain since you are the last handler of the patch.
> If neither is true, Paolo's SOB should be removed.

I didn't even remember writing this, but it's possible I pseudocoded in 
an email just like you did below.

>> -	return PT64_ROOT_4LEVEL;
>> +	bool la57 = (cr4_read_shadow() & X86_CR4_LA57) != 0;
>> +
>> +	return la57 ? PT64_ROOT_5LEVEL : PT64_ROOT_4LEVEL;
> 
> Why obfuscate this?  KVM is completely hosed if pgtable_l5_enabled() doesn't
> match host CR4.  E.g.
> 
> 	return pgtable_l5_enabled() ? PT64_ROOT_5LEVEL : PT64_ROOT_4LEVEL;

That also suggests the above pseudocoding scenario, where I'd be too 
lazy to look up the correct spelling of pgtable_l5_enabled().

Paolo

>>   #else
>>   	return PT32E_ROOT_LEVEL;
>>   #endif
>> @@ -462,11 +464,6 @@ static int has_svm(void)
>>   		return 0;
>>   	}
>>   
>> -	if (pgtable_l5_enabled()) {
>> -		pr_info("KVM doesn't yet support 5-level paging on AMD SVM\n");
>> -		return 0;
>> -	}
>> -
>>   	return 1;
>>   }
>>   
>> -- 
>> 2.31.1
>>
> 


  reply	other threads:[~2021-08-19 16:39 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-18 16:55 [PATCH v3 0/3] SVM 5-level page table support Wei Huang
2021-08-18 16:55 ` [PATCH v3 1/3] KVM: x86: Allow CPU to force vendor-specific TDP level Wei Huang
2021-08-18 16:55 ` [PATCH v3 2/3] KVM: x86: Handle the case of 5-level shadow page table Wei Huang
2021-08-18 17:15   ` Sean Christopherson
2021-08-19 16:36     ` Paolo Bonzini
2021-08-18 18:00   ` Tom Lendacky
2021-08-18 16:55 ` [PATCH v3 3/3] KVM: SVM: Add 5-level page table support for SVM Wei Huang
2021-08-18 17:32   ` Sean Christopherson
2021-08-19 16:38     ` Paolo Bonzini [this message]
2021-08-19 16:43 ` [PATCH v3 0/3] SVM 5-level page table support Paolo Bonzini
2021-08-23  9:20   ` Maxim Levitsky
2021-08-23 15:15     ` Wei Huang
2021-08-23 16:10       ` Sean Christopherson
2021-08-23 18:10         ` Maxim Levitsky
2021-08-23 18:06       ` Maxim Levitsky

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=d5894435-c5e1-890d-880c-6b6390fe50d8@redhat.com \
    --to=pbonzini@redhat.com \
    --cc=bp@alien8.de \
    --cc=hpa@zytor.com \
    --cc=jmattson@google.com \
    --cc=joro@8bytes.org \
    --cc=kvm@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@redhat.com \
    --cc=seanjc@google.com \
    --cc=tglx@linutronix.de \
    --cc=vkuznets@redhat.com \
    --cc=wanpengli@tencent.com \
    --cc=wei.huang2@amd.com \
    --cc=x86@kernel.org \
    --subject='Re: [PATCH v3 3/3] KVM: SVM: Add 5-level page table support for SVM' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).