[SRU][B][PATCH 0/2] Fix kvm crash in 4.15

[Sultan Alsawaf]

BugLink: https://bugs.launchpad.net/bugs/1881072

SRU Justification:

[Impact]
A commit from a 4.19 update upstream, "KVM: VMX: Zero out *all* general purpose
registers after VM-Exit", causes kvm to crash on i386.

[Fix]
4.19 recently received a fix for this issue ("KVM: VMX: Mark RCX, RDX and RSI as
clobbered in vmx_vcpu_run()'s asm blob"), but it requires another patch in 4.19
in order to compile on amd64 ("KVM: VMX: Explicitly reference RCX as the
vmx_vcpu pointer in asm blobs").

[Test]
1. Create an i386 VM with support for nested virtualization.
2. Run the following:
	qemu-system-x86_64 -enable-kvm -display none
3. Check dmesg

[Regression Potential]
Medium. These are upstream patches that are confirmed to fix the kvm crash, but
there's a bit of churn involved.

Sean Christopherson (2):
  KVM: VMX: Explicitly reference RCX as the vmx_vcpu pointer in asm
    blobs
  KVM: VMX: Mark RCX, RDX and RSI as clobbered in vmx_vcpu_run()'s asm
    blob

 arch/x86/kvm/vmx.c | 91 +++++++++++++++++++++++++---------------------
 1 file changed, 50 insertions(+), 41 deletions(-)

-- 
2.20.1