[v7,0/4] KVM: nSVM: ondemand nested state allocation

Message

Maxim Levitsky Oct. 1, 2020, 11:29 a.m. UTC

This is the next version of this patch series.

In V5 I adopted Sean Christopherson's suggestion to make .set_efer return
a negative error (-ENOMEM in this case) which in most cases in kvm
propagates to the userspace.

I noticed though that wrmsr emulation code doesn't do this and instead
it injects #GP to the guest on _any_ error.

So I fixed the wrmsr code to behave in a similar way to the rest
of the kvm code.
(#GP only on a positive error value, and forward the negative error to
the userspace)

I had to adjust one wrmsr handler (xen_hvm_config) to stop it from returning
negative values	so that new WRMSR emulation behavior doesn't break it.
This patch was only compile tested.

The memory allocation failure was tested by always returning -ENOMEM
from svm_allocate_nested.

The nested allocation itself was tested by countless attempts to run
nested guests, do nested migration on both my AMD and Intel machines.
I wasn't able to break it.

Changes from V5: addressed Sean Christopherson's review feedback.
Changes from V6: rebased the code on latest kvm/queue

Best regards,
	Maxim Levitsky

Maxim Levitsky (4):
  KVM: x86: xen_hvm_config: cleanup return values
  KVM: x86: report negative values from wrmsr emulation to userspace
  KVM: x86: allow kvm_x86_ops.set_efer to return an error value
  KVM: nSVM: implement on demand allocation of the nested state

 arch/x86/include/asm/kvm_host.h |  2 +-
 arch/x86/kvm/emulate.c          |  4 +--
 arch/x86/kvm/svm/nested.c       | 42 ++++++++++++++++++++++
 arch/x86/kvm/svm/svm.c          | 64 ++++++++++++++++++---------------
 arch/x86/kvm/svm/svm.h          | 10 +++++-
 arch/x86/kvm/vmx/vmx.c          |  6 ++--
 arch/x86/kvm/x86.c              | 39 ++++++++++----------
 7 files changed, 114 insertions(+), 53 deletions(-)

Comments

Paolo Bonzini Oct. 19, 2020, 3:52 p.m. UTC | #1

On 01/10/20 13:29, Maxim Levitsky wrote:
> This is the next version of this patch series.
> 
> In V5 I adopted Sean Christopherson's suggestion to make .set_efer return
> a negative error (-ENOMEM in this case) which in most cases in kvm
> propagates to the userspace.
> 
> I noticed though that wrmsr emulation code doesn't do this and instead
> it injects #GP to the guest on _any_ error.
> 
> So I fixed the wrmsr code to behave in a similar way to the rest
> of the kvm code.
> (#GP only on a positive error value, and forward the negative error to
> the userspace)
> 
> I had to adjust one wrmsr handler (xen_hvm_config) to stop it from returning
> negative values	so that new WRMSR emulation behavior doesn't break it.
> This patch was only compile tested.
> 
> The memory allocation failure was tested by always returning -ENOMEM
> from svm_allocate_nested.
> 
> The nested allocation itself was tested by countless attempts to run
> nested guests, do nested migration on both my AMD and Intel machines.
> I wasn't able to break it.
> 
> Changes from V5: addressed Sean Christopherson's review feedback.
> Changes from V6: rebased the code on latest kvm/queue
> 
> Best regards,
> 	Maxim Levitsky
> 
> Maxim Levitsky (4):
>   KVM: x86: xen_hvm_config: cleanup return values
>   KVM: x86: report negative values from wrmsr emulation to userspace
>   KVM: x86: allow kvm_x86_ops.set_efer to return an error value
>   KVM: nSVM: implement on demand allocation of the nested state
> 
>  arch/x86/include/asm/kvm_host.h |  2 +-
>  arch/x86/kvm/emulate.c          |  4 +--
>  arch/x86/kvm/svm/nested.c       | 42 ++++++++++++++++++++++
>  arch/x86/kvm/svm/svm.c          | 64 ++++++++++++++++++---------------
>  arch/x86/kvm/svm/svm.h          | 10 +++++-
>  arch/x86/kvm/vmx/vmx.c          |  6 ++--
>  arch/x86/kvm/x86.c              | 39 ++++++++++----------
>  7 files changed, 114 insertions(+), 53 deletions(-)
> 

Queued, thanks.

Paolo