Merge tag 'kvm-x86-fixes-6.12-rcN' of https://github.com/kvm-x86/linux into HEAD

KVM x86 and selftests fixes for 6.12:

 - Increase the timeout for the memslot performance selftest to avoid false
   failures on arm64 and nested x86 platforms.

 - Fix a goof in the guest_memfd selftest where a for-loop initialized a
   bit mask to zero instead of BIT(0).

 - Disable strict aliasing when building KVM selftests to prevent the
   compiler from treating things like "u64 *" to "uint64_t *" cases as
   undefined behavior, which can lead to nasty, hard to debug failures.

 - Force -march=x86-64-v2 for KVM x86 selftests if and only if the uarch
   is supported by the compiler.

 - When emulating a guest TLB flush for a nested guest, flush vpid01, not
   vpid02, if L2 is active but VPID is disabled in vmcs12, i.e. if L2 and
   L1 are sharing VPID '0' (from L1's perspective).

 - Fix a bug in the SNP initialization flow where KVM would return '0' to
   userspace instead of -errno on failure.