RE: [PATCH 3/6] x86/sev-es: Use __put_user()/__get_user

[David Laight]

From: Juergen Gross
> Sent: 12 May 2021 09:58
> 
> On 12.05.21 10:50, 'Joerg Roedel' wrote:
> > On Wed, May 12, 2021 at 10:16:12AM +0200, Juergen Gross wrote:
> >> You want something like xen_safe_[read|write]_ulong().
> >
> >  From a first glance I can't see it, what is the difference between the
> > xen_safe_*_ulong() functions and __get_user()/__put_user()? The only
> > difference I can see is that __get/__put_user() support different access
> > sizes, but neither of those disables page-faults by itself, for example.
> >
> > Couldn't these xen-specific functions not also be replaces by
> > __get_user()/__put_user()?
> 
> No, those were used before, but commit 9da3f2b7405440 broke Xen's use
> case. That is why I did commit 1457d8cf7664f.

I've just looked at 9da3f2b7405440.

It doesn't look right to me - wrong return value for a lot of cases.
OTOH it isn't in my newest tree at all.

If bogus_uaccess() is now elsewhere I can't see how (without changes)
it would allow through these faults.

	David

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