Re: [Qemu-devel] [PATCH 00/14] target-i386: Implement MPX extension

[Paolo Bonzini <pbonzini@redhat.com>]

On 09/07/2015 10:17, Richard Henderson wrote:
> I'm still in the process of testing this, as there's no code
> written for it yet and hardware to compare against doesn't
> start shipping until (probably) August.
> 
> But in the meantime there are a number of holes that I found
> in XSAVE support that might affect KVM, and one question wrt
> SMM support that affects MPX.  So I thought I'd get some 
> feedback on this sooner than later.
> 
> This patch set depends on the addressing cleanup patchset that
> I just posted.  It ought to depend on Pavel Dovgalyuk's exception
> handling cleanup patchset, but I haven't included that in my tree.
> 
> Comments?

Hi Richard, it would be nice to have these patches---or at least the
XSAVE support---in 2.6.  I also have a PKRU implementation for TCG, but
currently I'm only implementing RDPKRU/WRPKRU because I would like to
build the XSAVE support on top of your patches.

Regarding SMM support, there are three ways to go:

1) pester Intel some more so that they disclose the format of the SMM
state save area;

2) just place BNDCFGS at a random offset that is left as reserved in
AMD's manual;

3) do not save BNDCFGS at all since no one uses it anyway. *shrug*

The holes in the computation of KVM's hflags are probably harmless, but
nice to have anyway.  Thanks for fixing them.  Are there others that I
missed?

Paolo