Commit 11c5ad0ec441 ("eventpoll: switch to ->poll_mask") in v4.18-rc1, made
eventpoll switch from ->poll() to ->poll_mask(), resulting in a null
pointer dereference as vmmon calls the callback directly without checking
its availability.
Rather than calling the callback directly (which would result in null
pointer dereference), use vfs_poll() wrapper. As this wrapper is only
available since 4.18-rc1 cycle as well, provide a copy to use when building
against older kernels.
Note: even if the commit revealing the problem was reverted in 4.18-rc3
(and is unlikely to go back in the same form) so that vmmon no longer
crashes with 4.18 kernel, calling the callback without a check is a bad
practice so let's keep the patch in place.
The MSR_K7_HWCR_SMMLOCK macro is defined in mainline since commit
18c71ce9c882 ("x86/CPU/AMD: Add the Secure Encrypted Virtualization CPU
feature") in v4.16-rc1.
As discussed in
https://bugzilla.suse.com/show_bug.cgi?id=1059674
the reason for multiple objtool warnings is the fact that vmmon module
defines its own Panic() function which never returns. While it is marked as
such which is used by the compiler for optimization, there is no way to
find this from object file.
While this seems innocuous, it might result in problems with unwinder
later. The quickest way around is to replace vmmon's own Panic() with
standard kernel panic() until a cleaner solution is found.
The CR3_PCID_MASK is defined in mainline asm/processor-flags.h since
commit 6c690ee1039b ("x86/mm: Split read_cr3() into read_cr3_pa() and
__read_cr3()") in v4.13-rc1.
The MSR_MISC_FEATURES_ENABLES macro is defined in mainline since commit
ab6d9468631a ("x86/msr: Rename MISC_FEATURE_ENABLES to
MISC_FEATURES_ENABLES") in v4.12-rc1.
The MSR_MISC_FEATURES_ENABLES_CPUID_FAULT macro is defined in mainline
since commit e9ea1e7f53b8 ("x86/arch_prctl: Add ARCH_[GET|SET]_CPUID") in
v4.12-rc1.
Michal Kubecek