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

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Date:   Tue, 28 Mar 2023 12:51:32 -0500
From:   John Allen <john.allen@....com>
To:     "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
        "Yang, Weijiang" <weijiang.yang@...el.com>,
        "Christopherson, Sean" <seanjc@...gle.com>
Cc:     "thomas.lendacky@....com" <thomas.lendacky@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "x86@...nel.org" <x86@...nel.org>, Borislav Petkov <bp@...en8.de>
Subject: Re: [RFC PATCH 0/7] SVM guest shadow stack support

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?

Thanks,
John