From: Paolo Bonzini <pbonzini@redhat.com>
To: Gerd Hoffmann <kraxel@redhat.com>
Cc: "Daniel P. Berrangé" <berrange@redhat.com>,
qemu-devel@nongnu.org, "Sergio Lopez" <slp@redhat.com>,
"Eduardo Habkost" <eduardo@habkost.net>,
"Marcel Apfelbaum" <marcel.apfelbaum@gmail.com>,
"Richard Henderson" <richard.henderson@linaro.org>,
kvm@vger.kernel.org, "Marcelo Tosatti" <mtosatti@redhat.com>,
"Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [PATCH v4] x86: add etc/phys-bits fw_cfg file
Date: Thu, 22 Sep 2022 14:38:02 +0200 [thread overview]
Message-ID: <CABgObfavcPLUbMzaLQS2Rj2=r5eAhuBuKdiHQ4wJGfgPm_=XsQ@mail.gmail.com> (raw)
In-Reply-To: <20220922122058.vesh352623uaon6e@sirius.home.kraxel.org>
On Thu, Sep 22, 2022 at 2:21 PM Gerd Hoffmann <kraxel@redhat.com> wrote:
> No. This will basically inform the guest that host-phys-bits has been
> enabled (and pass the number of bits). So the firmware can make use of
> the available address space instead of trying to be as conservative as
> possible to avoid going beyond the (unknown) limit.
Intel processors that are not extremely old have host-phys-bits equal
to 39, 46 or 52. Older processors that had 36, in all likelihood,
didn't have IOMMUs (so no big 64-bit BARs).
AMD processors have had 48 for a while, though older consumer processors had 40.
QEMU has always used 40, though many downstream packages (IIRC RHEL
and Ubuntu) just use host-phys-bits = true when using KVM.
Would it work to:
1) set host-phys-bits to true on new machine types when not using TCG
(i.e. KVM / HVF / WHPX)
2) in the firmware treat 40 as if it were 39, to support old machine types?
Paolo
next prev parent reply other threads:[~2022-09-22 14:14 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-22 10:14 [PATCH v4] x86: add etc/phys-bits fw_cfg file Gerd Hoffmann
2022-09-22 11:24 ` Daniel P. Berrangé
2022-09-22 11:56 ` Michael S. Tsirkin
2022-09-22 12:20 ` Gerd Hoffmann
2022-09-22 12:38 ` Paolo Bonzini [this message]
2022-09-22 14:16 ` Gerd Hoffmann
2022-09-22 17:13 ` Jim Mattson
2022-09-22 19:49 ` Paolo Bonzini
2022-09-22 20:33 ` Gerd Hoffmann
2022-09-23 6:00 ` Paolo Bonzini
2022-09-23 6:23 ` Gerd Hoffmann
2022-10-07 13:44 ` Michael S. Tsirkin
2022-10-10 7:30 ` Gerd Hoffmann
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