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    SubjectRe: [PATCH v3 1/8] KVM:VMX: Define CET VMCS fields and bits
    On Thu, Feb 28, 2019 at 07:53:45AM -0800, Sean Christopherson wrote:
    > On Tue, Feb 26, 2019 at 11:31:11AM -0800, Jim Mattson wrote:
    > > On Mon, Feb 25, 2019 at 10:32 PM Yang Weijiang <weijiang.yang@intel.com> wrote:
    > > >
    > > > CET - Control-flow Enforcement Technology, it's used to
    > > > protect against return/jump oriented programming (ROP)
    > > > attacks. It provides the following capabilities to defend
    > > > against ROP/JOP style control-flow subversion attacks:
    > > > - Shadow Stack (SHSTK):
    > > > A second stack for the program that is
    > > > used exclusively for control transfer
    > > > operations.
    > > > - Indirect Branch Tracking (IBT):
    > > > Free branch protection to defend against
    > > > Jump/Call Oriented Programming.
    > > >
    > > > On processors that support CET, VMX saves/restores
    > > > the states of IA32_S_CET, SSP and IA32_INTR_SSP_TABL_ADDR MSR
    > > > to the VMCS area for Guest/Host unconditionally.
    > > >
    > > > If VM_EXIT_LOAD_HOST_CET_STATE = 1, the host CET MSRs are
    > > > restored from VMCS host-state area at VM exit as follows:
    > > >
    > > > - HOST_IA32_S_CET: Host supervisor mode IA32_S_CET MSR is loaded
    > > > from this field.
    > > >
    > > > - HOST_SSP : Host SSP is loaded from this field.
    > > >
    > > > - HOST_INTR_SSP_TABL_ADDR : Host IA32_INTR_SSP_TABL_ADDR
    > > > MSR is loaded from this field.
    > > >
    > > > If VM_ENTRY_LOAD_GUEST_CET_STATE = 1, the guest CET MSRs are loaded
    > > > from VMCS guest-state area at VM entry as follows:
    > > >
    > > > - GUEST_IA32_S_CET : Guest supervisor mode IA32_S_CET MSR is loaded
    > > > from this field.
    > > >
    > > > - GUEST_SSP : Guest SSP is loaded from this field.
    > > >
    > > > - GUEST_INTR_SSP_TABL_ADDR : Guest IA32_INTR_SSP_TABL_ADDR
    > > > MSR is loaded from this field.
    > > >
    > > > Additionally, to context switch guest and host CET states, the VMM
    > > > uses xsaves/xrstors instructions to save/restore the guest CET states
    > > > at VM exit/entry. The CET xsave area is within thread_struct.fpu area.
    > > > If OS execution flow changes during task switch/interrupt/exception etc.,
    > > > the OS also relies on xsaves/xrstors to switch CET states accordingly.
    > > >
    > > > Signed-off-by: Zhang Yi Z <yi.z.zhang@linux.intel.com>
    > > > Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
    > > > ---
    > > > arch/x86/include/asm/vmx.h | 8 ++++++++
    > > > 1 file changed, 8 insertions(+)
    > > >
    > > > diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
    > > > index ade0f153947d..395c1f7e5938 100644
    > > > --- a/arch/x86/include/asm/vmx.h
    > > > +++ b/arch/x86/include/asm/vmx.h
    > > > @@ -98,6 +98,7 @@
    > > > #define VM_EXIT_LOAD_IA32_EFER 0x00200000
    > > > #define VM_EXIT_SAVE_VMX_PREEMPTION_TIMER 0x00400000
    > > > #define VM_EXIT_CLEAR_BNDCFGS 0x00800000
    > > > +#define VM_EXIT_LOAD_HOST_CET_STATE 0x10000000
    > > >
    > > > #define VM_EXIT_ALWAYSON_WITHOUT_TRUE_MSR 0x00036dff
    > > >
    > > > @@ -109,6 +110,7 @@
    > > > #define VM_ENTRY_LOAD_IA32_PAT 0x00004000
    > > > #define VM_ENTRY_LOAD_IA32_EFER 0x00008000
    > > > #define VM_ENTRY_LOAD_BNDCFGS 0x00010000
    > > > +#define VM_ENTRY_LOAD_GUEST_CET_STATE 0x00100000
    > > >
    > > > #define VM_ENTRY_ALWAYSON_WITHOUT_TRUE_MSR 0x000011ff
    > > >
    > > > @@ -325,6 +327,9 @@ enum vmcs_field {
    > > > GUEST_PENDING_DBG_EXCEPTIONS = 0x00006822,
    > > > GUEST_SYSENTER_ESP = 0x00006824,
    > > > GUEST_SYSENTER_EIP = 0x00006826,
    > > > + GUEST_IA32_S_CET = 0x00006828,
    > > > + GUEST_SSP = 0x0000682a,
    > > > + GUEST_INTR_SSP_TABL_ADDR = 0x0000682c,
    > >
    > > Nit: TABL is an unusual abbreviation. Perhaps TBL here and below?
    >
    > I don't see any reason to abbreviate TABLE, we don't need the two
    > characters for anything.
    >
    > > And why did you drop the 'IA32' here, but not in GUEST_IA32_S_CET above?
    > > (It is true that there seems to be no rhyme or reason to the mnemonics
    > > chosen here. For example, EFER keeps its IA32, but SYSENTER_EIP
    > > doesn't. Sigh.)
    >
    > My vote is to always drop IA32, IMO it's redundant.

    How about GUEST_S_CET, GUEST_SSP and GUEST_INTR_SSP_TABLE?

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