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Re: [PATCH v2 2/2] hw/arm/virt: KVM: The IPA lower bound is 32
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From: |
Marc Zyngier |
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Subject: |
Re: [PATCH v2 2/2] hw/arm/virt: KVM: The IPA lower bound is 32 |
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Date: |
Thu, 11 Mar 2021 09:59:37 +0000 |
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User-agent: |
Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (Gojō) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) |
On Wed, 10 Mar 2021 13:52:18 +0000,
Andrew Jones <drjones@redhat.com> wrote:
>
> The virt machine already checks KVM_CAP_ARM_VM_IPA_SIZE to get the
> upper bound of the IPA size. If that bound is lower than the highest
> possible GPA for the machine, then QEMU will error out. However, the
> IPA is set to 40 when the highest GPA is less than or equal to 40,
> even when KVM may support an IPA limit as low as 32. This means KVM
> may fail the VM creation unnecessarily. Additionally, 40 is selected
> with the value 0, which means use the default, and that gets around
> a check in some versions of KVM, causing a difficult to debug fail.
> Always use the IPA size that corresponds to the highest possible GPA,
> unless it's lower than 32, in which case use 32. Also, we must still
> use 0 when KVM only supports the legacy fixed 40 bit IPA.
>
> Suggested-by: Marc Zyngier <maz@kernel.org>
> Signed-off-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Marc Zyngier <maz@kernel.org>
M.
--
Without deviation from the norm, progress is not possible.