From: Paolo Bonzini <pbonzini@redhat.com>
To: Maxim Levitsky <mlevitsk@redhat.com>, Li Qiang <liq3ea@gmail.com>
Cc: Qemu Developers <qemu-devel@nongnu.org>,
Avi Kivity <avi.kivity@gmail.com>
Subject: Re: Questions about the real mode in kvm/qemu
Date: Thu, 26 Sep 2019 11:18:30 +0200 [thread overview]
Message-ID: <23789310-35fb-8c93-44f4-532bcd34007d@redhat.com> (raw)
In-Reply-To: <3d3f3a0e6e796260348c66e69e859e1901501ee8.camel@redhat.com>
On 26/09/19 10:59, Maxim Levitsky wrote:
> If you mean to ask if there is a way to let guest access use no
> paging at all, that is access host physical addresses directly, then
> indeed there is no way, since regular non 'unrestricted guest' mode
> required both protected mode and paging, and 'unrestricted guest'
> requires EPT. Academically speaking it is of course possible to
> create paging tables that are 1:1...
Not so academically, it's exactly what KVM does. However, indeed it
would also be possible to switch out of EPT mode when CR0.PG=0. I'm not
sure why it was done this way, maybe when the code was written it was
simpler to use the identity map.
Let's see if Avi is listening... :)
Paolo
next prev parent reply other threads:[~2019-09-26 9:20 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-26 7:52 Questions about the real mode in kvm/qemu Li Qiang
2019-09-26 8:31 ` Maxim Levitsky
2019-09-26 8:52 ` Li Qiang
2019-09-26 8:59 ` Maxim Levitsky
2019-09-26 9:18 ` Paolo Bonzini [this message]
2019-09-26 9:24 ` Maxim Levitsky
2019-09-26 9:33 ` Paolo Bonzini
2019-09-26 9:41 ` Maxim Levitsky
2019-09-26 10:00 ` Paolo Bonzini
2019-09-26 10:03 ` Maxim Levitsky
2019-09-28 22:10 ` Avi Kivity
2019-09-29 7:39 ` Li Qiang
2019-09-26 9:15 ` Paolo Bonzini
2019-09-26 9:35 ` Maxim Levitsky
2019-09-26 9:35 ` Li Qiang
2019-09-26 9:53 ` Paolo Bonzini
2019-09-26 11:47 ` Li Qiang
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