Re: [PATCH RFC] virtio-spec: flexible configuration layout

On 11/09/2011 05:19 PM, Michael S. Tsirkin wrote:

On Wed, Nov 09, 2011 at 02:48:58PM +0200, Sasha Levin wrote:

quoted

On Wed, 2011-11-09 at 14:38 +0200, Avi Kivity wrote:

quoted

On 11/09/2011 10:46 AM, Sasha Levin wrote:

quoted

quoted

Alternatively we can add new structures with new
structure IDs, pointed to from PCI configuration space.

As we don't yet have devices or drivers with 64 bit features,
I decided we don't need high feature bits in legacy space.
This also frees up feature bit 31 as we don't need it
to enable high feature bits anymore.

KVM tool actually has support for 64bit features, we can probably remove
that when Pekka isn't looking :)

What about the Windows drivers?

While 64-bit features were defined, there was no actual devices to use
them.

So even if Windows drivers had the ability to support 64-bit features,
no device ever needed it therefore no device ever activated it.

A potential issue might arise when we remap feature bit 31 to do
something else, and when activated it would fool Windows drivers to
think that 64-bit features are now activated, while they're not - but
thats not something that should happen since legacy layout shouldn't
have that field enabled as per the spec (no new features in legacy
code).

I was unable to check if it was actually implemented in the drivers
because
http://git.kernel.org/?p=virt/kvm/kvm-guest-drivers-windows.git;a=summary is not quite there (*cough*).

https://github.com/YanVugenfirer/kvm-guest-drivers-windows

I'm pretty sure windows drivers didn't yet get to it.
This was out for a very short time.

quoted

-- 

Sasha.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/