From: Gerd Hoffmann <kraxel@redhat.com>
To: Xiaoyao Li <xiaoyao.li@intel.com>
Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org,
Marcelo Tosatti <mtosatti@redhat.com>,
Marcel Apfelbaum <marcel.apfelbaum@gmail.com>,
Eduardo Habkost <eduardo@habkost.net>,
Paolo Bonzini <pbonzini@redhat.com>,
Richard Henderson <richard.henderson@linaro.org>,
"Michael S. Tsirkin" <mst@redhat.com>,
Sergio Lopez <slp@redhat.com>
Subject: Re: [PATCH 0/2] expose host-phys-bits to guest
Date: Thu, 1 Sep 2022 15:58:10 +0200 [thread overview]
Message-ID: <20220901135810.6dicz4grhz7ye2u7@sirius.home.kraxel.org> (raw)
In-Reply-To: <957f0cc5-6887-3861-2b80-69a8c7cdd098@intel.com>
Hi,
> I think the problem is for all the named CPU model, that they don't have
> phys_bits defined. Thus they all have "cpu->phys-bits == 0", which leads to
> cpu->phys_bits = TCG_PHYS_ADDR_BITS (36 for 32-bits build and 40 for 64-bits
> build)
Exactly. And if you run on hardware with phys-bits being 36 or 39
(common for intel desktop processors) things explode when the guest
tries to use the whole range.
> Anyway, IMO, guest including guest firmware, should always consult from
> CPUID leaf 0x80000008 for physical address length.
It simply can't for the reason outlined above. Even if we fix qemu
today that doesn't solve the problem for the firmware because we want
backward compatibility with older qemu versions. Thats why I want the
extra bit which essentially says "CPUID leaf 0x80000008 actually works".
take care,
Gerd
next prev parent reply other threads:[~2022-09-01 13:58 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-31 12:50 [PATCH 0/2] expose host-phys-bits to guest Gerd Hoffmann
2022-08-31 12:50 ` [PATCH 1/2] [hack] reserve bit KVM_HINTS_HOST_PHYS_BITS Gerd Hoffmann
2022-08-31 13:05 ` Michael S. Tsirkin
2022-08-31 12:50 ` [PATCH 2/2] [RfC] expose host-phys-bits to guest Gerd Hoffmann
2022-08-31 12:58 ` Claudio Fontana
2022-09-01 6:07 ` [PATCH 0/2] " Xiaoyao Li
2022-09-01 13:58 ` Gerd Hoffmann [this message]
2022-09-01 14:36 ` Xiaoyao Li
2022-09-01 16:17 ` Gerd Hoffmann
2022-09-02 0:10 ` Xiaoyao Li
2022-09-02 6:07 ` Gerd Hoffmann
2022-09-02 6:35 ` Michael S. Tsirkin
2022-09-02 8:44 ` Gerd Hoffmann
2022-09-04 20:37 ` Michael S. Tsirkin
2022-09-05 7:39 ` Gerd Hoffmann
2022-09-01 14:55 ` Claudio Fontana
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