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Re: [PATCH 8/8] hw/arm/virt: Disable highmem when on hypervisor.framewor

From: Eduardo Habkost
Subject: Re: [PATCH 8/8] hw/arm/virt: Disable highmem when on hypervisor.framework
Date: Fri, 27 Nov 2020 12:17:57 -0500

On Fri, Nov 27, 2020 at 04:53:59PM +0000, Peter Maydell wrote:
> On Fri, 27 Nov 2020 at 16:47, Eduardo Habkost <ehabkost@redhat.com> wrote:
> > Do you know how the implicitly-accelerator-specific code is
> > implemented?  PARange is in id_aa64mmfr0, correct?  I don't see
> > any accel-specific code for initializing id_aa64mmfr0.
> For TCG, the value of id_aa64mmfr0 is set by the per-cpu
> init functions aarch64_a57_initfn(), aarch64_a72_initfn(), etc.
> For KVM, if we're using "-cpu cortex-a53" or "-cpu cortex-a57"
> these only work if the host CPU really is an A53 or A57, in
> which case the reset value set by the initfn is correct.
> In the more usual case of "-cpu host", we ask the kernel for
> the ID register values in kvm_arm_get_host_cpu_features(),
> which is part of the implementation of
> kvm_arm_set_cpu_features_from_host(), which gets called
> in aarch64_max_initfn() (inside a kvm_enabled() conditional).
> So there is a *_enabled() check involved, which I hadn't
> realised until I worked back up to where this stuff is called.

Thanks!  Is the data returned by kvm_arm_get_host_cpu_features()
supposed to eventually affect the value of id_aa64mmfr0?  I don't
see how that could happen.


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