On Thu, Mar 30, 2023 at 01:37:38PM +0800, Yang, Weijiang wrote: > > On 3/29/2023 8:16 AM, Yang, Weijiang wrote: > > > > 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@xxxxxxxxx/ > > > > > > > > > > [2]: Latest CET kernel patches > > > > > > > > > > https://lore.kernel.org/all/20220929222936.14584-1-rick.p.edgecombe@xxxxxxxxx/ > > > > > > > > > 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. > > Patch 1/7 did what I wanted to implement to support AMD SHSTK, my next > version > > will continue refactoring them in vmx scope, then your series may pick up > the helper > > and modify accordingly. > > Please note, in my series, I removed check for MSR_IA32_PL{0,1,2}_SSP since > they're > > not supported right now, but your series supports for the MSRs, so you have > to change > > the helper a bit to adapt to your patches. The reason we decided to include the PL{0,1,2}_SSP MSRs is that even though linux doesn't support supervisor shadow stack, a non-linux guest OS might support it and could make use of the MSRs. It could be something the vmx patches might want to account for as well Thanks, John
