Messages in this thread | | | Subject | Re: [PATCH v14 00/13] Introduce support for guest CET feature | From | Paolo Bonzini <> | Date | Thu, 28 Jan 2021 18:57:00 +0100 |
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On 06/11/20 02:16, Yang Weijiang wrote: > Control-flow Enforcement Technology (CET) provides protection against > Return/Jump-Oriented Programming (ROP/JOP) attack. There're two CET > sub-features: Shadow Stack (SHSTK) and Indirect Branch Tracking (IBT). > SHSTK is to prevent ROP programming and IBT is to prevent JOP programming. > > Several parts in KVM have been updated to provide VM CET support, including: > CPUID/XSAVES config, MSR pass-through, user space MSR access interface, > vmentry/vmexit config, nested VM etc. These patches have dependency on CET > kernel patches for xsaves support and CET definitions, e.g., MSR and related > feature flags. > > CET kernel patches are here: > SHSTK: https://lkml.kernel.org/r/20201012153850.26996-1-yu-cheng.yu@intel.com/ > IBT: https://lkml.kernel.org/r/20201012154530.28382-1-yu-cheng.yu@intel.com/ > > CET QEMU patch: > https://patchwork.ozlabs.org/project/qemu-devel/patch/20201013051935.6052-2-weijiang.yang@intel.com/ > KVM Unit test: > https://patchwork.kernel.org/project/kvm/patch/20200506082110.25441-12-weijiang.yang@intel.com/ > > v14: > - Sean refactored v13 patchset then came out v14-rc1, this version is > rebased on top of 5.10-rc1 and tested on TGL. > - Fixed a few minor issues found during test, such as nested CET broken, > call-trace and guest reboot failure etc. > - Original v14-rc1 is here: https://github.com/sean-jc/linux/tree/vmx/cet. > > v13: > - Added CET definitions as a separate patch to facilitate KVM test. > - Disabled CET support in KVM if unrestricted_guest is turned off since > in this case CET related instructions/infrastructure cannot be emulated > well. > > v12: > - Fixed a few issues per Sean and Paolo's review feeback. > - Refactored patches to make them properly arranged. > - Removed unnecessary hard-coded CET states for host/guest. > - Added compile-time assertions for vmcs_field_to_offset_table to detect > mismatch of the field type and field encoding number. > - Added a custom MSR MSR_KVM_GUEST_SSP for guest active SSP save/restore. > - Rebased patches to 5.7-rc3. > > v11: > - Fixed a guest vmentry failure issue when guest reboots. > - Used vm_xxx_control_{set, clear}bit() to avoid side effect, it'll > clear cached data instead of pure VMCS field bits. > - Added vcpu->arch.guest_supported_xss dedidated for guest runtime mask, > this avoids supported_xss overwritten issue caused by an old qemu. > - Separated vmentry/vmexit state setting with CR0/CR4 dependency check > to make the patch more clear. > - Added CET VMCS states in dump_vmcs() for debugging purpose. > - Other refactor based on testing. > - This patch serial is built on top of below branch and CET kernel patches > for seeking xsaves support. > > v10: > - Refactored code per Sean's review feedback. > - Added CET support for nested VM. > - Removed fix-patch for CPUID(0xd,N) enumeration as this part is done > by Paolo and Sean. > - This new patchset is based on Paolo's queued cpu_caps branch. > - Modified patch per XSAVES related change. > - Consolidated KVM unit-test patch with KVM patches. > > v9: > - Refactored msr-check functions per Sean's feedback. > - Fixed a few issues per Sean's suggestion. > - Rebased patch to kernel-v5.4. > - Moved CET CPUID feature bits and CR4.CET to last patch. > > v8: > - Addressed Jim and Sean's feedback on: 1) CPUID(0xD,i) enumeration. 2) > sanity check when configure guest CET. 3) function improvement. > - Added more sanity check functions. > - Set host vmexit default status so that guest won't leak CET status to > host when vmexit. > - Added CR0.WP vs. CR4.CET mutual constrains. > > v7: > - Rebased patch to kernel v5.3 > - Sean suggested to change CPUID(0xd, n) enumeration code as alined with > existing one, and I think it's better to make the fix as an independent patch > since XSS MSR are being used widely on X86 platforms. > - Check more host and guest status before configure guest CET > per Sean's feedback. > - Add error-check before guest accesses CET MSRs per Sean's feedback. > - Other minor fixes suggested by Sean. > > v6: > - Rebase patch to kernel v5.2. > - Move CPUID(0xD, n>=1) helper to a seperate patch. > - Merge xsave size fix with other patch. > - Other minor fixes per community feedback. > > v5: > - Rebase patch to kernel v5.1. > - Wrap CPUID(0xD, n>=1) code to a helper function. > - Pass through MSR_IA32_PL1_SSP and MSR_IA32_PL2_SSP to Guest. > - Add Co-developed-by expression in patch description. > - Refine patch description. > > v4: > - Add Sean's patch for loading Guest fpu state before access XSAVES > managed CET MSRs. > - Melt down CET bits setting into CPUID configuration patch. > - Add VMX interface to query Host XSS. > - Check Host and Guest XSS support bits before set Guest XSS. > - Make Guest SHSTK and IBT feature enabling independent. > - Do not report CET support to Guest when Host CET feature is Disabled. > > v3: > - Modified patches to make Guest CET independent to Host enabling. > - Added patch 8 to add user space access for Guest CET MSR access. > - Modified code comments and patch description to reflect changes. > > v2: > - Re-ordered patch sequence, combined one patch. > - Added more description for CET related VMCS fields. > - Added Host CET capability check while enabling Guest CET loading bit. > - Added Host CET capability check while reporting Guest CPUID(EAX=7, EXC=0). > - Modified code in reporting Guest CPUID(EAX=D,ECX>=1), make it clearer. > - Added Host and Guest XSS mask check while setting bits for Guest XSS. > > > Sean Christopherson (2): > KVM: x86: Report XSS as an MSR to be saved if there are supported features > KVM: x86: Load guest fpu state when accessing MSRs managed by XSAVES > > Yang Weijiang (11): > KVM: x86: Refresh CPUID on writes to MSR_IA32_XSS > KVM: x86: Add #CP support in guest exception dispatch > KVM: VMX: Introduce CET VMCS fields and flags > KVM: x86: Add fault checks for CR4.CET > KVM: VMX: Emulate reads and writes to CET MSRs > KVM: VMX: Add a synthetic MSR to allow userspace VMM to access GUEST_SSP > KVM: x86: Report CET MSRs as to-be-saved if CET is supported > KVM: x86: Enable CET virtualization for VMX and advertise CET to userspace > KVM: VMX: Pass through CET MSRs to the guest when supported > KVM: nVMX: Add helper to check the vmcs01 MSR bitmap for MSR pass-through > KVM: nVMX: Enable CET support for nested VMX > > arch/x86/include/asm/kvm_host.h | 4 +- > arch/x86/include/asm/vmx.h | 8 ++ > arch/x86/include/uapi/asm/kvm.h | 1 + > arch/x86/include/uapi/asm/kvm_para.h | 1 + > arch/x86/kvm/cpuid.c | 26 +++- > arch/x86/kvm/vmx/capabilities.h | 5 + > arch/x86/kvm/vmx/nested.c | 57 ++++++-- > arch/x86/kvm/vmx/vmcs12.c | 6 + > arch/x86/kvm/vmx/vmcs12.h | 14 +- > arch/x86/kvm/vmx/vmx.c | 207 ++++++++++++++++++++++++++- > arch/x86/kvm/x86.c | 56 +++++++- > arch/x86/kvm/x86.h | 10 +- > 12 files changed, 370 insertions(+), 25 deletions(-) >
I reviewed the patch and it is mostly okay. However, if I understand it correctly, it will not do anything until host support materializes, because otherwise XSS will be 0.
If this is the case, I plan to apply locally v15 and hold on it until the host code is committed.
Paolo
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