On Wed, Apr 18, 2018 at 11:18:28AM +0800, Youquan Song wrote:
From: KarimAllah Ahmed karahmed@amazon.de
(cherry picked from commit d28b387fb74da95d69d2615732f50cceb38e9a4d)
[ Based on a patch from Ashok Raj ashok.raj@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]
Signed-off-by: KarimAllah Ahmed karahmed@amazon.de Signed-off-by: David Woodhouse dwmw@amazon.co.uk Signed-off-by: Thomas Gleixner tglx@linutronix.de Reviewed-by: Darren Kenny darren.kenny@oracle.com Reviewed-by: Konrad Rzeszutek Wilk konrad.wilk@oracle.com Reviewed-by: Jim Mattson jmattson@google.com Cc: Andrea Arcangeli aarcange@redhat.com Cc: Andi Kleen ak@linux.intel.com Cc: Jun Nakajima jun.nakajima@intel.com Cc: kvm@vger.kernel.org Cc: Dave Hansen dave.hansen@intel.com Cc: Tim Chen tim.c.chen@linux.intel.com Cc: Andy Lutomirski luto@kernel.org Cc: Asit Mallick asit.k.mallick@intel.com Cc: Arjan Van De Ven arjan.van.de.ven@intel.com Cc: Greg KH gregkh@linuxfoundation.org Cc: Paolo Bonzini pbonzini@redhat.com Cc: Dan Williams dan.j.williams@intel.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Ashok Raj ashok.raj@intel.com Link: https://lkml.kernel.org/r/1517522386-18410-5-git-send-email-karahmed@amazon.... Signed-off-by: David Woodhouse dwmw@amazon.co.uk Signed-off-by: Yi Sun yi.y.sun@linux.intel.com [v4.4 backport]
Conflicts: arch/x86/kvm/vmx.c
yet again...