[for-5.0] Deprecate KVM support for AArch32

[for-5.0] Deprecate KVM support for AArch32

[Peter Maydell]

The Linux kernel has dropped support for allowing 32-bit Arm systems
to host KVM guests (kernel commit 541ad0150ca4aa663a2, which just
landed upstream in the 5.7 merge window).  Mark QEMU's support for
this configuration as deprecated, so that we can delete that support
code in 5.2.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
I was reading the 5.7 merge window writeup on LWN this weekend
and saw that the dropping of 32-bit support had gone in; just
enough time to squeeze our deprecation warning into 5.0 so we
can drop the code in 5.2 rather than 6.0...

 docs/system/deprecated.rst | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/docs/system/deprecated.rst b/docs/system/deprecated.rst
index c633fe2beff..3142fac3865 100644
--- a/docs/system/deprecated.rst
+++ b/docs/system/deprecated.rst
@@ -336,6 +336,14 @@ The ``compat`` property used to set backwards compatibility modes for
 the processor has been deprecated. The ``max-cpu-compat`` property of
 the ``pseries`` machine type should be used instead.
 
+KVM guest support on 32-bit Arm hosts (since 5.0)
+'''''''''''''''''''''''''''''''''''''''''''''''''
+
+The Linux kernel has dropped support for allowing 32-bit Arm systems
+to host KVM guests as of the 5.7 kernel. Accordingly, QEMU is deprecating
+its support for this configuration and will remove it in a future version.
+Running 32-bit guests on a 64-bit Arm host remains supported.
+
 System emulator devices
 -----------------------
 
-- 
2.20.1

Re: [for-5.0] Deprecate KVM support for AArch32

[Andrew Jones]

On Tue, Apr 14, 2020 at 01:09:35PM +0100, Peter Maydell wrote:
> The Linux kernel has dropped support for allowing 32-bit Arm systems
> to host KVM guests (kernel commit 541ad0150ca4aa663a2, which just
> landed upstream in the 5.7 merge window).  Mark QEMU's support for
> this configuration as deprecated, so that we can delete that support
> code in 5.2.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
> I was reading the 5.7 merge window writeup on LWN this weekend
> and saw that the dropping of 32-bit support had gone in; just
> enough time to squeeze our deprecation warning into 5.0 so we
> can drop the code in 5.2 rather than 6.0...
> 
>  docs/system/deprecated.rst | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/docs/system/deprecated.rst b/docs/system/deprecated.rst
> index c633fe2beff..3142fac3865 100644
> --- a/docs/system/deprecated.rst
> +++ b/docs/system/deprecated.rst
> @@ -336,6 +336,14 @@ The ``compat`` property used to set backwards compatibility modes for
>  the processor has been deprecated. The ``max-cpu-compat`` property of
>  the ``pseries`` machine type should be used instead.
>  
> +KVM guest support on 32-bit Arm hosts (since 5.0)
> +'''''''''''''''''''''''''''''''''''''''''''''''''
> +
> +The Linux kernel has dropped support for allowing 32-bit Arm systems
> +to host KVM guests as of the 5.7 kernel. Accordingly, QEMU is deprecating
> +its support for this configuration and will remove it in a future version.
> +Running 32-bit guests on a 64-bit Arm host remains supported.
> +
>  System emulator devices
>  -----------------------
>  
> -- 
> 2.20.1
> 
>

Reviewed-by: Andrew Jones <drjones@redhat.com>

Re: [for-5.0] Deprecate KVM support for AArch32

[Richard Henderson]

On 4/14/20 5:09 AM, Peter Maydell wrote:
> The Linux kernel has dropped support for allowing 32-bit Arm systems
> to host KVM guests (kernel commit 541ad0150ca4aa663a2, which just
> landed upstream in the 5.7 merge window).  Mark QEMU's support for
> this configuration as deprecated, so that we can delete that support
> code in 5.2.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
> I was reading the 5.7 merge window writeup on LWN this weekend
> and saw that the dropping of 32-bit support had gone in; just
> enough time to squeeze our deprecation warning into 5.0 so we
> can drop the code in 5.2 rather than 6.0...
> 
>  docs/system/deprecated.rst | 8 ++++++++
>  1 file changed, 8 insertions(+)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~

Re: [for-5.0] Deprecate KVM support for AArch32

[Daniel P. Berrangé]

On Tue, Apr 14, 2020 at 01:09:35PM +0100, Peter Maydell wrote:
> The Linux kernel has dropped support for allowing 32-bit Arm systems
> to host KVM guests (kernel commit 541ad0150ca4aa663a2, which just
> landed upstream in the 5.7 merge window).  Mark QEMU's support for
> this configuration as deprecated, so that we can delete that support
> code in 5.2.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
> I was reading the 5.7 merge window writeup on LWN this weekend
> and saw that the dropping of 32-bit support had gone in; just
> enough time to squeeze our deprecation warning into 5.0 so we
> can drop the code in 5.2 rather than 6.0...
> 
>  docs/system/deprecated.rst | 8 ++++++++
>  1 file changed, 8 insertions(+)

The docs are sufficient to start the deprecation process, but
we might consider also having a warning from configure, or a
message on stderr at runtime to make it more visible to users.

> 
> diff --git a/docs/system/deprecated.rst b/docs/system/deprecated.rst
> index c633fe2beff..3142fac3865 100644
> --- a/docs/system/deprecated.rst
> +++ b/docs/system/deprecated.rst
> @@ -336,6 +336,14 @@ The ``compat`` property used to set backwards compatibility modes for
>  the processor has been deprecated. The ``max-cpu-compat`` property of
>  the ``pseries`` machine type should be used instead.
>  
> +KVM guest support on 32-bit Arm hosts (since 5.0)
> +'''''''''''''''''''''''''''''''''''''''''''''''''
> +
> +The Linux kernel has dropped support for allowing 32-bit Arm systems
> +to host KVM guests as of the 5.7 kernel. Accordingly, QEMU is deprecating
> +its support for this configuration and will remove it in a future version.
> +Running 32-bit guests on a 64-bit Arm host remains supported.
> +

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>


Regards,
Daniel
-- 
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Re: [for-5.0] Deprecate KVM support for AArch32

[Peter Maydell]

On Wed, 15 Apr 2020 at 13:33, Daniel P. Berrangé <berrange@redhat.com> wrote:
>
> On Tue, Apr 14, 2020 at 01:09:35PM +0100, Peter Maydell wrote:
> > The Linux kernel has dropped support for allowing 32-bit Arm systems
> > to host KVM guests (kernel commit 541ad0150ca4aa663a2, which just
> > landed upstream in the 5.7 merge window).  Mark QEMU's support for
> > this configuration as deprecated, so that we can delete that support
> > code in 5.2.
> >
> > Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> > ---
> > I was reading the 5.7 merge window writeup on LWN this weekend
> > and saw that the dropping of 32-bit support had gone in; just
> > enough time to squeeze our deprecation warning into 5.0 so we
> > can drop the code in 5.2 rather than 6.0...
> >
> >  docs/system/deprecated.rst | 8 ++++++++
> >  1 file changed, 8 insertions(+)
>
> The docs are sufficient to start the deprecation process, but
> we might consider also having a warning from configure, or a
> message on stderr at runtime to make it more visible to users.

Mmm. I didn't feel entirely comfortable making code changes to
print messages at this point in the 5.0 release cycle, though.

thanks
-- PMM

Re: [for-5.0] Deprecate KVM support for AArch32

[Daniel P. Berrangé]

On Wed, Apr 15, 2020 at 01:41:05PM +0100, Peter Maydell wrote:
> On Wed, 15 Apr 2020 at 13:33, Daniel P. Berrangé <berrange@redhat.com> wrote:
> >
> > On Tue, Apr 14, 2020 at 01:09:35PM +0100, Peter Maydell wrote:
> > > The Linux kernel has dropped support for allowing 32-bit Arm systems
> > > to host KVM guests (kernel commit 541ad0150ca4aa663a2, which just
> > > landed upstream in the 5.7 merge window).  Mark QEMU's support for
> > > this configuration as deprecated, so that we can delete that support
> > > code in 5.2.
> > >
> > > Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> > > ---
> > > I was reading the 5.7 merge window writeup on LWN this weekend
> > > and saw that the dropping of 32-bit support had gone in; just
> > > enough time to squeeze our deprecation warning into 5.0 so we
> > > can drop the code in 5.2 rather than 6.0...
> > >
> > >  docs/system/deprecated.rst | 8 ++++++++
> > >  1 file changed, 8 insertions(+)
> >
> > The docs are sufficient to start the deprecation process, but
> > we might consider also having a warning from configure, or a
> > message on stderr at runtime to make it more visible to users.
> 
> Mmm. I didn't feel entirely comfortable making code changes to
> print messages at this point in the 5.0 release cycle, though.

Sure, that's understandable.

Regards,
Daniel
-- 
|: https://berrange.com      -o-    https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org         -o-            https://fstop138.berrange.com :|
|: https://entangle-photo.org    -o-    https://www.instagram.com/dberrange :|

Re: [for-5.0] Deprecate KVM support for AArch32

[Alex Bennée]

Peter Maydell <peter.maydell@linaro.org> writes:

> The Linux kernel has dropped support for allowing 32-bit Arm systems
> to host KVM guests (kernel commit 541ad0150ca4aa663a2, which just
> landed upstream in the 5.7 merge window).  Mark QEMU's support for
> this configuration as deprecated, so that we can delete that support
> code in 5.2.
>
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

> ---
> I was reading the 5.7 merge window writeup on LWN this weekend
> and saw that the dropping of 32-bit support had gone in; just
> enough time to squeeze our deprecation warning into 5.0 so we
> can drop the code in 5.2 rather than 6.0...
>
>  docs/system/deprecated.rst | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/docs/system/deprecated.rst b/docs/system/deprecated.rst
> index c633fe2beff..3142fac3865 100644
> --- a/docs/system/deprecated.rst
> +++ b/docs/system/deprecated.rst
> @@ -336,6 +336,14 @@ The ``compat`` property used to set backwards compatibility modes for
>  the processor has been deprecated. The ``max-cpu-compat`` property of
>  the ``pseries`` machine type should be used instead.
>  
> +KVM guest support on 32-bit Arm hosts (since 5.0)
> +'''''''''''''''''''''''''''''''''''''''''''''''''
> +
> +The Linux kernel has dropped support for allowing 32-bit Arm systems
> +to host KVM guests as of the 5.7 kernel. Accordingly, QEMU is deprecating
> +its support for this configuration and will remove it in a future version.
> +Running 32-bit guests on a 64-bit Arm host remains supported.
> +
>  System emulator devices
>  -----------------------


-- 
Alex Bennée