LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Yu Zhang <yu.c.zhang@linux.intel.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>,
	Wei Huang <wei.huang2@amd.com>,
	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 v2 1/3] KVM: x86: Allow CPU to force vendor-specific TDP level
Date: Tue, 10 Aug 2021 19:00:31 +0800	[thread overview]
Message-ID: <20210810110031.h7vaqf3nljwm3wym@linux.intel.com> (raw)
In-Reply-To: <0ac41a07-beeb-161e-9e5d-e45477106c01@redhat.com>

On Tue, Aug 10, 2021 at 11:25:27AM +0200, Paolo Bonzini wrote:
> On 10/08/21 09:40, Yu Zhang wrote:
> > About "host can't easily mirror L1's desired paging mode", could you please elaborate?
> > Thanks!
> 
> Shadow pgae tables in KVM will always have 3 levels on 32-bit machines and
> 4/5 levels on 64-bit machines.  L1 instead might have any number of levels
> from 2 to 5 (though of course not more than the host has).

Thanks Paolo.

I guess it's because, unlike EPT which are with either 4 or 5 levels, NPT's
level can range from 2 to 5, depending on the host paging mode...

> 
> Therefore, when shadowing 32-bit NPT page tables, KVM has to add extra fixed
> levels on top of those that it's shadowing.  See mmu_alloc_direct_roots for
> the code.

So when shadowing NPTs(can be 2/3 levels, depending on the paging mode in L1),
and if L0 Linux is running in 4/5 level mode, extra levels of paging structures
is needed in the shadow NPT.

But shadow EPT does not have such annoyance. Is above understanding correct?

B.R.
Yu

  reply	other threads:[~2021-08-10 11:00 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 [this message]
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
2021-08-08 19:26 ` [PATCH v2 3/3] KVM: SVM: Add 5-level page table support for SVM Wei Huang

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=20210810110031.h7vaqf3nljwm3wym@linux.intel.com \
    --to=yu.c.zhang@linux.intel.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=pbonzini@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 v2 1/3] KVM: x86: Allow CPU to force vendor-specific TDP level' \
    /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).