[Bug]: VMs don't start with Hyper-V enabled on Intel Xeon CPUs with AMX

[mikhail-kovalev-secforge]

Version

trunk/main

Host OS Type

Windows

Host OS name + version

Windows 11 Build 26200

Host Architecture

x86

Guest OS Type

all

Guest Architecture

x86

Guest OS name + version

No response

Component

Unspecified

What happened?

VirtualBox fails to start with Hyper-V enabled if XSAVE area is larger than 8192 bytes. This is the case, e.g., on Xeon CPUs with AMX.

00:00:03.962190 CPUM: Matched host CPU INTEL 0x6/0x8f/0x8 Intel_Core7_SapphireRapids with CPU DB entry 'Intel Core i7-6700K' (INTEL 0x6/0x5e/0x3 Intel_Core7_Skylake)
00:00:03.962264 CPUM: MXCSR_MASK=0xffff (host: 0xffff)
00:00:03.962287 CPUM: Microcode revision 0x2B000620
00:00:03.962299 CPUM: Changing leaf 13[0]: EBX=0x2b00 -> 0x340, ECX=0x2b00 -> 0x340
00:00:03.962314 CPUM: MSR/CPUID reconciliation insert: 0x0000010b IA32_FLUSH_CMD
00:00:03.962319 CPUM: MSR/CPUID reconciliation insert: 0x0000010a IA32_ARCH_CAPABILITIES
00:00:03.962324 CPUM: MSR fudge: 0x00000122 IA32_TSX_CTRL
00:00:03.962328 CPUM: MSR fudge: 0x00000123 IA32_MCU_OPT_CTRL
00:00:03.962341 CPUM: SetGuestCpuIdFeature: Enabled SYSENTER/EXIT
00:00:03.962345 CPUM: SetGuestCpuIdFeature: Enabled SYSCALL/RET
00:00:03.962348 CPUM: SetGuestCpuIdFeature: Enabled PAE
00:00:03.962353 CPUM: SetGuestCpuIdFeature: Enabled LAHF/SAHF
00:00:03.962356 CPUM: SetGuestCpuIdFeature: Enabled NX
00:00:03.962359 CPUM: SetGuestCpuIdFeature: Enabled LONG MODE
00:00:03.962363 CPUM: Enabled MTRR read-write support
00:00:03.962368 CPUM: Enabled fixed-range MTRRs and 16 (virtualized) variable-range MTRRs
00:00:03.965941 NEM: HvPartitionPropertyProcessorVendor=0x1 (1)
00:00:03.967097 NEM: cbXSaveArea=10752
00:00:03.967121 AssertLogRel C:\workspace\VirtualBox\src\VBox\VMM\VMMR3\NEMR3Native-win.cpp(1770) int __cdecl nemR3NativeInitAfterCPUM(struct VM *): pVM->nem.s.cbXSaveArea <= sizeof(pVCpu->cpum.GstCtx.XState)
00:00:03.967127 Returned XSAVE area exceeds what VirtualBox supported (10752 > 8192)
00:00:03.967135 NEM: Destroying partition 00000214739ec080 with its 4 VCpus...

Is this an architectural limitation?

How can we reproduce this?

Enable VBS and try to start a VM.

Did you upload all of your necessary log files, screenshots, etc.?

• Yes, I've uploaded all pertinent files to this issue.