Re: [RFC PATCH 0/7] SVM guest shadow stack support

["Yang, Weijiang" <weijiang.yang@intel.com>]

On 3/29/2023 1:51 AM, John Allen wrote:
> On Wed, Jan 25, 2023 at 01:11:44AM +0000, Edgecombe, Rick P wrote:
>> On Wed, 2023-01-25 at 00:55 +0000, Sean Christopherson wrote:
>>> On Wed, Oct 12, 2022, John Allen wrote:
>>>> AMD Zen3 and newer processors support shadow stack, a feature
>>>> designed to
>>>> protect against ROP (return-oriented programming) attacks in which
>>>> an attacker
>>>> manipulates return addresses on the call stack in order to execute
>>>> arbitrary
>>>> code. To prevent this, shadow stacks can be allocated that are only
>>>> used by
>>>> control transfer and return instructions. When a CALL instruction
>>>> is issued, it
>>>> writes the return address to both the program stack and the shadow
>>>> stack. When
>>>> the subsequent RET instruction is issued, it pops the return
>>>> address from both
>>>> stacks and compares them. If the addresses don't match, a control-
>>>> protection
>>>> exception is raised.
>>>>
>>>> Shadow stack and a related feature, Indirect Branch Tracking (IBT),
>>>> are
>>>> collectively referred to as Control-flow Enforcement Technology
>>>> (CET). However,
>>>> current AMD processors only support shadow stack and not IBT.
>>>>
>>>> This series adds support for shadow stack in SVM guests and builds
>>>> upon the
>>>> support added in the CET guest support patch series [1] and the CET
>>>> kernel
>>>> patch series [2]. Additional patches are required to support shadow
>>>> stack
>>>> enabled guests in qemu [3] and glibc [4].
>>>>
>>>> [1]: CET guest support patches
>>>>
>> https://lore.kernel.org/all/20220616084643.19564-1-weijiang.yang@intel.com/
>>>> [2]: Latest CET kernel patches
>>>>
>> https://lore.kernel.org/all/20220929222936.14584-1-rick.p.edgecombe@intel.com/
>>> That dependency chain makes me sad.
>>>
>>> Outside of a very shallow comment on the last patch, I don't plan on
>>> reviewing
>>> this until the kernel side of things gets out of our way.  When that
>>> finally
>>> does happen, I'll definitely prioritize reviewing and merging this
>>> and the KVM
>>> Intel series.  I'd love to see this land.
>> I think all KVM needs is a few patches from the beginning of the host
>> series (the FPU stuff). At one point Weijiang and I had discussed with
>> Paolo and x86 folks that those few could go up with the KVM series if
>> desired.
> Now that the baremetal series has been accepted, how do we want to
> proceed? I think I'd like to send a refreshed version based on the
> version that was accpeted, but I'd want to wait to base it on a new
> version of Weijiang's kvm/vmx series (if one is planned).
>
> Weijiang and Rick,
>
> Are you planning on sending a new version of the kvm/vmx series?

Hi, Allen,

Yes, I'm working on the new version of kvm/vmx series, will cc you when

send it to community.


>
> Thanks,
> John