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

[Khaled Elmously]

On 2020-05-28 12:56:01 , Sultan Alsawaf wrote:
> 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(-)
> 

Acked-by: Khalid Elmously <khalid.elmously at canonical.com>