CVM: Set GuestCrashRegsAvailable in cpuid

[smalis-msft]

We support these regs on all backends, so no reason not to.

[chris-oo]

Do we need to maybe filter offering this diagnostic on if cvm tracing is enabled?
This is what I see now in a debug build:

[kmsg]: [2.166324] virt_mshv_vtl::processor: INFO  Guest has reported system crash crash=VtlCrash { vp_index: VpIndex(0), last_vtl: Vtl0, control: GuestCrashCtl { pre_os_id: 0, no_crash_dump: false, crash_message: true, crash_notify: true }, parameters: [800000000000001a, 0, 72e, 33d85cb0, 85] }
[kmsg]: [2.166707] underhill_core::dispatch: INFO  Notifying the host of the guest system crash VtlCrash { vp_index: VpIndex(0), last_vtl: Vtl0, control: GuestCrashCtl { pre_os_id: 0, no_crash_dump: false, crash_message: true, crash_notify: true }, parameters: [800000000000001a, 0, 72e, 33d85cb0, 85] }
[kmsg]: [2.167256] firmware_uefi: WARN  unknown uefi write addr=0x2c data=0x1
[kmsg]: [2.167828] vmm_core::partition_unit::vp_set: ERROR  rax=0x800000000000001a rcx=0x72e rdx=0x0 rbx=0x0 rsp=0x33d85c58 rbp=0x33d86d10 rsi=0x66083198 rdi=0x72e r8=0x72e r9=0x0 r10=0x0 r11=0x1b r12=0x80000000 r13=0x33db2458 r14=0x1 r15=0x80000000 rip=0x66af0c34 rflags=0x10206
[kmsg]: [2.168161] vmm_core::partition_unit::vp_set: ERROR  cs=SegmentRegister { base: 0, limit: ffffffff, selector: 38, attributes: a09b } ds=SegmentRegister { base: 0, limit: ffffffff, selector: 30, attributes: c093 } es=SegmentRegister { base: 0, limit: ffffffff, selector: 30, attributes: c093 } fs=SegmentRegister { base: 0, limit: ffffffff, selector: 30, attributes: c093 } gs=SegmentRegister { base: 0, limit: ffffffff, selector: 30, attributes: c093 } ss=SegmentRegister { base: 0, limit: ffffffff, selector: 30, attributes: c093 } tr=SegmentRegister { base: 33dbca30, limit: 67, selector: 20, attributes: 8b } ldtr=SegmentRegister { base: 0, limit: ffff, selector: 0, attributes: 82 } gdtr=TableRegister { base: 66bc7000, limit: 47 } idtr=TableRegister { base: 0, limit: 0 } cr0=0x80010033 cr2=0x0 cr3=0x33801000 cr4=0x660 cr8=0x0 efer=0xd00
[kmsg]: [2.169456] vmm_core::partition_unit::vp_set: ERROR  faulting instruction instruction="ud2" bytes=[f, b, eb, fc, cc, cc, cc, cc, cc, cc, cc, cc, cc, cc, cc, cc]
[kmsg]: [2.169608] vmm_core::partition_unit::vp_set: ERROR  triple fault vtl=Vtl0

versus before:

[kmsg]: [2.186469] underhill_core::dispatch: INFO  starting VM boot_time_ms=0x1b17 boot_time="6.9353505s"
[kmsg]: [2.189205] firmware_uefi: WARN  unknown uefi write addr=0x2b data=0x77000
[kmsg]: [2.230847] vmm_core::partition_unit::vp_set: ERROR  rax=0x800000000000001a rcx=0x72e rdx=0x0 rbx=0x0 rsp=0x33d85c58 rbp=0x33d86d10 rsi=0x66083198 rdi=0x72e r8=0x72e r9=0x0 r10=0x0 r11=0x1b r12=0x80000000 r13=0x33db2458 r14=0x1 r15=0x80000000 rip=0x66af0c34 rflags=0x10206
[kmsg]: [2.231072] vmm_core::partition_unit::vp_set: ERROR  cs=SegmentRegister { base: 0, limit: ffffffff, selector: 38, attributes: a09b } ds=SegmentRegister { base: 0, limit: ffffffff, selector: 30, attributes: c093 } es=SegmentRegister { base: 0, limit: ffffffff, selector: 30, attributes: c093 } fs=SegmentRegister { base: 0, limit: ffffffff, selector: 30, attributes: c093 } gs=SegmentRegister { base: 0, limit: ffffffff, selector: 30, attributes: c093 } ss=SegmentRegister { base: 0, limit: ffffffff, selector: 30, attributes: c093 } tr=SegmentRegister { base: 33dbca30, limit: 67, selector: 20, attributes: 8b } ldtr=SegmentRegister { base: 0, limit: ffff, selector: 0, attributes: 82 } gdtr=TableRegister { base: 66bc7000, limit: 47 } idtr=TableRegister { base: 0, limit: 0 } cr0=0x80010033 cr2=0x0 cr3=0x33801000 cr4=0x660 cr8=0x0 efer=0xd00
[kmsg]: [2.232417] vmm_core::partition_unit::vp_set: ERROR  faulting instruction instruction="ud2" bytes=[f, b, eb, fc, cc, cc, cc, cc, cc, cc, cc, cc, cc, cc, cc, cc]
[kmsg]: [2.232491] vmm_core::partition_unit::vp_set: ERROR  triple fault vtl=Vtl0

[chris-oo]

I think also, we may want to print the crash message within UH itself?

[smmalis37]

We don't need to filter this on cvm tracing, it is the responsibility of the guest to not send secret data to these. However the crash message is a different story, since I believe it's just a pointer into guest memory, so that we would have to be careful about reading and sharing.

[chris-oo]

I guess if we emit the guest message as a normal tracing call, then we'll follow whatever the normal filtering logic is. I think though, we should emit the message because OHCL is may be the only thing that can actually read it, the host can't.