On Thu, Feb 1, 2018 at 1:59 PM, KarimAllah Ahmed <karah...@amazon.de> wrote:
> [ Based on a patch from Ashok Raj <ashok....@intel.com> ]
> Add direct access to MSR_IA32_SPEC_CTRL for guests. This is needed for
> guests that will only mitigate Spectre V2 through IBRS+IBPB and will not
> be using a retpoline+IBPB based approach.
> To avoid the overhead of saving and restoring the MSR_IA32_SPEC_CTRL for
> guests that do not actually use the MSR, only start saving and restoring
> when a non-zero is written to it.
> No attempt is made to handle STIBP here, intentionally. Filtering STIBP
> may be added in a future patch, which may require trapping all writes
> if we don't want to pass it through directly to the guest.
> [dwmw2: Clean up CPUID bits, save/restore manually, handle reset]
> Cc: Asit Mallick <asit.k.mall...@intel.com>
> Cc: Arjan Van De Ven <arjan.van.de....@intel.com>
> Cc: Dave Hansen <dave.han...@intel.com>
> Cc: Andi Kleen <a...@linux.intel.com>
> Cc: Andrea Arcangeli <aarca...@redhat.com>
> Cc: Linus Torvalds <torva...@linux-foundation.org>
> Cc: Tim Chen <tim.c.c...@linux.intel.com>
> Cc: Thomas Gleixner <t...@linutronix.de>
> Cc: Dan Williams <dan.j.willi...@intel.com>
> Cc: Jun Nakajima <jun.nakaj...@intel.com>
> Cc: Paolo Bonzini <pbonz...@redhat.com>
> Cc: David Woodhouse <d...@amazon.co.uk>
> Cc: Greg KH <gre...@linuxfoundation.org>
> Cc: Andy Lutomirski <l...@kernel.org>
> Cc: Ashok Raj <ashok....@intel.com>
> Signed-off-by: KarimAllah Ahmed <karah...@amazon.de>
> Signed-off-by: David Woodhouse <d...@amazon.co.uk>

Reviewed-by: Jim Mattson <jmatt...@google.com>

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