From: Lai Jiangshan <jiangshanlai@gmail.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
kvm@vger.kernel.org, Sean Christopherson <seanjc@google.com>,
Lai Jiangshan <jiangshan.ljs@antgroup.com>,
Jonathan Corbet <corbet@lwn.net>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
X86 ML <x86@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
linux-doc@vger.kernel.org
Subject: Re: [PATCH 2/2] KVM: X86/MMU: Introduce role.passthrough for shadowing 5-level NPT for 4-level NPT L1 guest
Date: Thu, 21 Apr 2022 08:23:32 +0800 [thread overview]
Message-ID: <CAJhGHyARz6rPZ+yJfkGPCbtZJnnMnODSD8szs7YYNVceCXhbSQ@mail.gmail.com> (raw)
In-Reply-To: <3e6018ad-06b7-f465-7b74-aeb20bca9489@redhat.com>
On Thu, Apr 21, 2022 at 1:15 AM Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> Looks good, and is easy to backport; thanks.
>
> However, once we have also your series "KVM: X86/MMU: Use one-off
> special shadow page for special roots", perhaps the passthrough sp can
> be converted to a special root (but now with a shadow_page) as well?
>
It will be much more complicated.
The current code allows fast_pgd_switch() for shadowing 5-level NPT
for 4-level NPT L1 guests because both the host and the guest are
64 bit. Using a special shadow page will disallow fast_pgd_switch().
And it will make using_special_root_page() more complicated.
It will require a different kind of special shadow page to make it
able to do fast switch.
prev parent reply other threads:[~2022-04-21 0:23 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-20 13:12 [PATCH 0/2] KVM: X86/MMU: Fix problem for shadowing 5-level NPT for 4-level NPT L1 guest Lai Jiangshan
2022-04-20 13:12 ` [PATCH 1/2] KVM: X86/MMU: Add sp_has_gptes() Lai Jiangshan
2022-04-20 20:48 ` Paolo Bonzini
2022-04-20 13:12 ` [PATCH 2/2] KVM: X86/MMU: Introduce role.passthrough for shadowing 5-level NPT for 4-level NPT L1 guest Lai Jiangshan
2022-04-20 17:15 ` Paolo Bonzini
2022-04-21 0:23 ` Lai Jiangshan [this message]
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