Bionic update to v4.15.2 stable release

SRU Justification

    Impact:
       The upstream process for stable tree updates is quite similar
       in scope to the Ubuntu SRU process, e.g., each patch has to
       demonstrably fix a bug, and each patch is vetted by upstream
       by originating either directly from a mainline/stable Linux tree or
       a minimally backported form of that patch. The v4.15.2 upstream stable
       patch set is now available. It should be included in the Ubuntu
       kernel as well.

       git://git.kernel.org/

    TEST CASE: TBD

       The following patches from the v4.15.2 stable release shall be applied:

KVM: x86: Make indirect calls in emulator speculation safe
KVM: VMX: Make indirect call speculation safe
module/retpoline: Warn about missing retpoline in module
x86/cpufeatures: Add CPUID_7_EDX CPUID leaf
x86/cpufeatures: Add Intel feature bits for Speculation Control
x86/cpufeatures: Add AMD feature bits for Speculation Control
x86/msr: Add definitions for new speculation control MSRs
x86/pti: Do not enable PTI on CPUs which are not vulnerable to Meltdown
x86/cpufeature: Blacklist SPEC_CTRL/PRED_CMD on early Spectre v2 microcodes
x86/speculation: Add basic IBPB (Indirect Branch Prediction Barrier) support
x86/alternative: Print unadorned pointers
x86/nospec: Fix header guards names
x86/bugs: Drop one "mitigation" from dmesg
x86/cpu/bugs: Make retpoline module warning conditional
x86/cpufeatures: Clean up Spectre v2 related CPUID flags
x86/retpoline: Simplify vmexit_fill_RSB()
x86/speculation: Simplify indirect_branch_prediction_barrier()
auxdisplay: img-ascii-lcd: add missing MODULE_DESCRIPTION/AUTHOR/LICENSE
iio: adc/accel: Fix up module licenses
pinctrl: pxa: pxa2xx: add missing MODULE_DESCRIPTION/AUTHOR/LICENSE
ASoC: pcm512x: add missing MODULE_DESCRIPTION/AUTHOR/LICENSE
KVM: nVMX: Eliminate vmcs02 pool
KVM: VMX: introduce alloc_loaded_vmcs
objtool: Improve retpoline alternative handling
objtool: Add support for alternatives at the end of a section
objtool: Warn on stripped section symbol
x86/mm: Fix overlap of i386 CPU_ENTRY_AREA with FIX_BTMAP
x86/spectre: Check CONFIG_RETPOLINE in command line parser
x86/entry/64: Remove the SYSCALL64 fast path
x86/entry/64: Push extra regs right away
x86/asm: Move 'status' from thread_struct to thread_info
Documentation: Document array_index_nospec
array_index_nospec: Sanitize speculative array de-references
x86: Implement array_index_mask_nospec
x86: Introduce barrier_nospec
x86: Introduce __uaccess_begin_nospec() and uaccess_try_nospec
x86/usercopy: Replace open coded stac/clac with __uaccess_{begin, end}
x86/uaccess: Use __uaccess_begin_nospec() and uaccess_try_nospec
x86/get_user: Use pointer masking to limit speculation
x86/syscall: Sanitize syscall table de-references under speculation
vfs, fdtable: Prevent bounds-check bypass via speculative execution
nl80211: Sanitize array index in parse_txq_params
x86/spectre: Report get_user mitigation for spectre_v1
x86/spectre: Fix spelling mistake: "vunerable"-> "vulnerable"
x86/cpuid: Fix up "virtual" IBRS/IBPB/STIBP feature bits on Intel
x86/speculation: Use Indirect Branch Prediction Barrier in context switch
x86/paravirt: Remove 'noreplace-paravirt' cmdline option
KVM: VMX: make MSR bitmaps per-VCPU
x86/kvm: Update spectre-v1 mitigation
x86/retpoline: Avoid retpolines for built-in __init functions
x86/spectre: Simplify spectre_v2 command line parsing
x86/pti: Mark constant arrays as __initconst
x86/speculation: Fix typo IBRS_ATT, which should be IBRS_ALL
KVM/x86: Update the reverse_cpuid list to include CPUID_7_EDX
KVM/x86: Add IBPB support
KVM/VMX: Emulate MSR_IA32_ARCH_CAPABILITIES
KVM/VMX: Allow direct access to MSR_IA32_SPEC_CTRL
KVM/SVM: Allow direct access to MSR_IA32_SPEC_CTRL
serial: core: mark port as initialized after successful IRQ change
fpga: region: release of_parse_phandle nodes after use
Linux 4.15.2