vfio-native/patches/README.md

Patchsets, by the detection each one clears

Every patch here is grouped by the VMAware check it targets, so a patchset can be taken or left on its own. Apply from the relevant source root with patch -p1 < <file>.

KVM - kvm/

Built against kernel 7.2.x. Builds as arch/x86/kvm only, about five minutes; no full kernel build is needed. See packaging/ for a PKGBUILD that does it and keeps it rebuilt.

Patch	Clears	What it does
0001-KVM-SVM-intercept-GP-when-guest-EFER.SVME-is-clear	SVM_EXCEPTIONS	Closes a FIXME KVM already carries: a CPL3 SVM instruction faults #GP where hardware gives #UD.
0002-KVM-x86-emulator-UD-not-GP-for-VMCALL-at-CPL-0	KVM_INTERCEPTION	Adds PrivUD so VMCALL at CPL>0 raises #UD like hardware.
0003-KVM-x86-UD-for-KVM-hypercalls-issued-at-CPL-0	KVM_INTERCEPTION	A CPL>0 hypercall raised no exception at all; now raises #UD.
0004-KVM-SVM-intercept-ICEBP-and-skip-it-before-injecting-its-DB	DBVM	SVM re-injected the ICEBP #DB with RIP still on the F1 byte; VMX and hardware report the next instruction.
0005-KVM-selftests-verify-ICEBP-DB-reports-RIP-past-the-ICEBP	-	The selftest for 0004: fails on unpatched SVM, passes with it.
EXPERIMENTAL-0006-runtime-cpuid-passthrough	TIMER	Drops CPUID and RDPRU interception on a 1:1-pinned vCPU and reprograms the AMD Processor Name String MSRs so raw CPUID still returns the declared brand. Opt-in via the cpuid_passthrough module parameter.

0002 and 0003 are a pair. Either alone leaves KVM_INTERCEPTION standing, because the check tries two stubs and only reports the first one that misbehaves.

The first five are written to be acceptable upstream: they make KVM match the architecture rather than add anything on top of it, each carries its rationale in the commit message, and all four pass checkpatch.pl --strict. 0000-cover-letter.txt is the series cover letter. They have been tested on AMD only; 0002 and 0003 are vendor-neutral code and the Intel reasoning is in the cover letter.

EXPERIMENTAL-0006 is built into the vfio-native-kvm-dkms package but off by default. It removes the cost the TIMER instruction-latency detector measures, and with it the guest reads raw host CPUID, so it applies itself only to vCPU threads confined to exactly one CPU and must be enabled through the cpuid_passthrough module parameter after the guest has booted. docs/ANALYSIS.md has the measurements and the constraints.

QEMU - qemu/

Against QEMU v11.1.1. Apply in numeric order.

Patch	Clears
01-firmware	FIRMWARE - ACPI link-device names, PNP0A06 stubs, FADT C-state latencies
02-disk-identity	VIRTUAL_DISK, DISK_SERIAL - QEMU HARDDISK, empty serials, SCSI inquiry strings
03-pci-ids	PCI_VENDOR, DEVICES - Red Hat/QEMU vendor and subsystem IDs, ICH9 layout
04-fw-cfg	QEMU_FW_CFG - the fw_cfg device signature
05-usb-hid	QEMU_USB - USB HID descriptor strings
06-audio	DEVICES - HDA codec and controller identity
07-edid	none. Carried for other detectors; VMAware does not read EDID.
08-cpu-misc	none. CPU feature plumbing and one upstream backport.

patch -p1 < qemu/01-firmware.patch and so on, then build with the prefix set to /opt so the system QEMU package is left alone:

./configure --prefix=/opt/qemu-native --target-list=x86_64-softmmu
ninja -C build && ninja -C build install

Approaches tried and rejected - kept so they are not re-derived

Approach	Result
Patched OVMF firmware (edk2)	Builds, then hangs before console init at 100% CPU, cause undiagnosed. Stock OVMF is fine and costs only the boot-logo warning.
TSC compensation for TIMER (BetterTiming)	No detection change, 6x slower boot.
CPUID leaf override (Hypervisor-Phantom)	Halved the timing signature, still detected, and added a SINGLE_STEP detection.
Clearing INTERCEPT_CPUID outright	Guest never boots.
Intercept clearing, minimal hypercall	Triple fault, or no effect.

TIMER has two detectors that OR together. The exception-latency one passes on stock KVM once it is measured the way VMAware measures it; the instruction-latency one is removable with EXPERIMENTAL-0006. docs/ANALYSIS.md has the measurements, including a direct reproduction of both in bench/timerprobe.c.

Identity values in these patches

Several patches carry a concrete make and model because no real machine leaves the field blank. Every one of them is a placeholder. Change them before you use this, or a detector gains a fingerprint shared by everyone who ran the same patch series.

Where	Value	Replace with
02-disk-identity	disk serial S0123456789ABCD	set <serial> on the disk in the domain XML; this fallback then never runs
02-disk-identity	disk and optical drive model strings	a drive you actually own, from lsblk -o NAME,MODEL
07-edid	monitor vendor and model	your own panel, from edid-decode < /sys/class/drm/*/edid

The SMBIOS values are not patched into QEMU at all - they are domain XML, taken from a real machine with dmidecode. Change every serial there too.