RE: [PATCH for-4.14 0/9] XSA-320 follow for IvyBridge

[Paul Durrant <xadimgnik@gmail.com>]

> -----Original Message-----
> From: Xen-devel <xen-devel-bounces@lists.xenproject.org> On Behalf Of Andrew Cooper
> Sent: 15 June 2020 15:15
> To: Xen-devel <xen-devel@lists.xenproject.org>
> Cc: Wei Liu <wl@xen.org>; Paul Durrant <paul@xen.org>; Andrew Cooper <andrew.cooper3@citrix.com>; Jan
> Beulich <JBeulich@suse.com>; Ian Jackson <Ian.Jackson@citrix.com>; Roger Pau Monné
> <roger.pau@citrix.com>
> Subject: [PATCH for-4.14 0/9] XSA-320 follow for IvyBridge
> 
> This is some work in light of IvyBridge not gaining microcode to combat SRBDS
> / XSA-320.  It is a mix of some work I'd planned for 4.15, and some patches
> posted already and delayed due to dependence's I'd discovered after-the-fact.
> 
> This provides a more user-friendly way of making IvyBridge safe by default
> without encountering migration incompatibilities.
> 
> In terms of functionality, it finishes the "fresh boot" vs "migrate/restore
> from pre-4.14" split in the libxc CPUID logic, and uses this to let us safely
> hide features by default without breaking the "divine what a guest may have
> seen previously" logic on migrate.
> 
> On top of that, we hide RDRAND by default to mitigate XSA-320.
> 
> Additionally, take the opportunity of finally getting this logic working to
> hide MPX by default (as posted previously), due to upcoming Intel timelines.
> 
> Request for 4.14.  The IvyBridge angle only became apparent after the public
> embargo on Tue 9th.  Otherwise, I would have made a concerted effort to get
> this logic sorted sooner and/or part of XSA-320 itself.
> 
> Strictly speaking, patches 1-4 aren't necessary, but without them the logic is
> very confusing to follow, particularly the reasoning about the safely of later
> changes.  As it is a simple set of transforms, we're better with them than
> without.
> 
> Also, the MPX patch isn't related to the RDRAND issue, but I was planning to
> get it into 4.14 already, until realising that the migration path was broken.
> Now that the path is fixed for the RDRAND issue, include the MPX patch as it
> pertains to future hardware compatibility (and would be backported to 4.14.1
> if it misses 4.14.0).
> 

Fair enough. Once the series has all the requisite maintainer acks then I'll release-ack it.

  Paul

> Andrew Cooper (9):
>   tools/libx[cl]: Introduce struct xc_xend_cpuid for xc_cpuid_set()
>   tests/cpu-policy: Confirm that CPUID serialisation is sorted
>   tools/libx[cl]: Move processing loop down into xc_cpuid_set()
>   tools/libx[cl]: Merge xc_cpuid_set() into xc_cpuid_apply_policy()
>   tools/libx[cl]: Plumb bool restore down into xc_cpuid_apply_policy()
>   x86/gen-cpuid: Distinguish default vs max in feature annotations
>   x86/hvm: Disable MPX by default
>   x86/cpuid: Introduce missing feature adjustment in calculate_pv_def_policy()
>   x86/spec-ctrl: Hide RDRAND by default on IvyBridge
> 
>  docs/misc/xen-command-line.pandoc           |  20 ++-
>  tools/libxc/include/xenctrl.h               |  42 ++++-
>  tools/libxc/xc_cpuid_x86.c                  | 239 ++++++++++++++++------------
>  tools/libxl/libxl.h                         |   8 +-
>  tools/libxl/libxl_cpuid.c                   |  17 +-
>  tools/libxl/libxl_create.c                  |   2 +-
>  tools/libxl/libxl_dom.c                     |   2 +-
>  tools/libxl/libxl_internal.h                |  12 +-
>  tools/libxl/libxl_nocpuid.c                 |   2 +-
>  tools/tests/cpu-policy/test-cpu-policy.c    |  49 +++++-
>  xen/arch/x86/cpuid.c                        |  23 +++
>  xen/include/public/arch-x86/cpufeatureset.h |   4 +-
>  xen/tools/gen-cpuid.py                      |  18 +--
>  13 files changed, 278 insertions(+), 160 deletions(-)
> 
> --
> 2.11.0
>