From: Sean Christopherson <seanjc@google.com>
To: harry harry <hiharryharryharry@gmail.com>
Cc: Maxim Levitsky <mlevitsk@redhat.com>,
kvm@vger.kernel.org, qemu-devel@nongnu.org,
Sean Christopherson <sean.j.christopherson@intel.com>,
Paolo Bonzini <pbonzini@redhat.com>,
stefanha@redhat.com, mathieu.tarral@protonmail.com
Subject: Re: About two-dimensional page translation (e.g., Intel EPT) and shadow page table in Linux QEMU/KVM
Date: Wed, 14 Jul 2021 17:47:42 +0000 [thread overview]
Message-ID: <YO8jPvScgCmtj0JP@google.com> (raw)
In-Reply-To: <CA+-xGqOSd0yhU4fEcobf3tW0mLb0TmLGycTwXNVUteyvvnXjdw@mail.gmail.com>
On Wed, Jul 14, 2021, harry harry wrote:
> > Heh, because the MMUs are all per-vCPU, it actually wouldn't be that much effort
> > beyond supporting !TDP and TDP for different VMs...
>
> Sorry, may I know what do you mean by "MMUs are all per-vCPU"? Do you
> mean the MMUs walk the page tables of each vCPU?
No, each vCPU has its own MMU instance, where an "MMU instance" is (mostly) a KVM
construct. Per-vCPU MMU instances are necessary because each vCPU has its own
relevant state, e.g. CR0, CR4, EFER, etc..., that affects the MMU instance in
some way. E.g. the MMU instance is used to walk guest page tables when
translating GVA->GPA for emulation, so per-vCPU MMUs are necessary even when
using TDP.
However, shadow/TDP PTEs are shared between compatible MMU instances. E.g. in
the common case where all vCPUs in a VM use identical settings, there will
effectively be a single set of TDP page tables shared by all vCPUs.
next prev parent reply other threads:[~2021-07-14 17:47 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-11 20:13 About two-dimensional page translation (e.g., Intel EPT) and shadow page table in Linux QEMU/KVM harry harry
2021-07-12 9:49 ` Maxim Levitsky
2021-07-12 13:02 ` harry harry
2021-07-12 13:11 ` Maxim Levitsky
2021-07-12 14:56 ` Sean Christopherson
2021-07-14 5:30 ` harry harry
2021-07-14 17:47 ` Sean Christopherson [this message]
2021-07-15 5:49 ` harry harry
2021-07-15 22:24 ` Sean Christopherson
2021-07-16 3:20 ` harry harry
2021-07-21 21:00 ` Sean Christopherson
2021-07-28 19:00 ` harry harry
2021-07-28 20:01 ` Sean Christopherson
2021-08-05 19:42 ` harry harry
2021-07-14 5:22 ` harry harry
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