Merge tag 'kvm-x86-fixes-6.19-rc8' of https://github.com/kvm-x86/linux into HEAD

Merge tag 'kvm-x86-fixes-6.19-rc8' of https://github.com/kvm-x86/linux into HEAD

Final KVM fixes for 6.19:

 - Fix a bug where AVIC is incorrectly inhibited when running with x2AVIC
   disabled via module param (or on a system without x2AVIC).

 - Fix a dangling device posted IRQs bug by explicitly checking if the irqfd is
   still active (on the list) when handling an eventfd signal, instead of
   zeroing the irqfd's routing information when the irqfd is deassigned.
   Zeroing the irqfd's routing info causes arm64 and x86's to not disable
   posting for the IRQ (kvm_arch_irq_bypass_del_producer() looks for an MSI),
   incorrectly leaving the IRQ in posted mode (and leading to use-after-free
   and memory leaks on AMD in particular).

   This is both the most pressing and scariest, but it's been in -next for
   a while.

 - Disable FORTIFY_SOURCE for KVM selftests to prevent the compiler from
   generating calls to the checked versions of memset() and friends, which
   leads to unexpected page faults in guest code due e.g. __memset_chk@plt
   not being resolved.

 - Explicitly configure the support XSS from within {svm,vmx}_set_cpu_caps() to
   fix a bug where VMX will compute the reference VMCS configuration with SHSTK
   and IBT enabled, but then compute each CPUs local config with SHSTK and IBT
   disabled if not all CET xfeatures are enabled, e.g. if the kernel is built
   with X86_KERNEL_IBT=n.  The mismatch in features results in differing nVMX
   setting, and ultimately causes kvm-intel.ko to refuse to load with nested=1.