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706d51681d
linux_dsm_epyc7002/arch/x86/kernel
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Sai Praneeth 706d51681d x86/speculation: Support Enhanced IBRS on future CPUs 
Future Intel processors will support "Enhanced IBRS" which is an "always
on" mode i.e. IBRS bit in SPEC_CTRL MSR is enabled once and never
disabled.

From the specification [1]:

 "With enhanced IBRS, the predicted targets of indirect branches
  executed cannot be controlled by software that was executed in a less
  privileged predictor mode or on another logical processor. As a
  result, software operating on a processor with enhanced IBRS need not
  use WRMSR to set IA32_SPEC_CTRL.IBRS after every transition to a more
  privileged predictor mode. Software can isolate predictor modes
  effectively simply by setting the bit once. Software need not disable
  enhanced IBRS prior to entering a sleep state such as MWAIT or HLT."

If Enhanced IBRS is supported by the processor then use it as the
preferred spectre v2 mitigation mechanism instead of Retpoline. Intel's
Retpoline white paper [2] states:

 "Retpoline is known to be an effective branch target injection (Spectre
  variant 2) mitigation on Intel processors belonging to family 6
  (enumerated by the CPUID instruction) that do not have support for
  enhanced IBRS. On processors that support enhanced IBRS, it should be
  used for mitigation instead of retpoline."

The reason why Enhanced IBRS is the recommended mitigation on processors
which support it is that these processors also support CET which
provides a defense against ROP attacks. Retpoline is very similar to ROP
techniques and might trigger false positives in the CET defense.

If Enhanced IBRS is selected as the mitigation technique for spectre v2,
the IBRS bit in SPEC_CTRL MSR is set once at boot time and never
cleared. Kernel also has to make sure that IBRS bit remains set after
VMEXIT because the guest might have cleared the bit. This is already
covered by the existing x86_spec_ctrl_set_guest() and
x86_spec_ctrl_restore_host() speculation control functions.

Enhanced IBRS still requires IBPB for full mitigation.

[1] Speculative-Execution-Side-Channel-Mitigations.pdf
[2] Retpoline-A-Branch-Target-Injection-Mitigation.pdf
Both documents are available at:
https://bugzilla.kernel.org/show_bug.cgi?id=199511

Originally-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim C Chen <tim.c.chen@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Ravi Shankar <ravi.v.shankar@intel.com>
Link: https://lkml.kernel.org/r/1533148945-24095-1-git-send-email-sai.praneeth.prakhya@intel.com
2018-08-03 12:50:34 +02:00
..
acpi x86/acpi: Prevent X2APIC id 0xffffffff from being accounted 2018-04-17 11:56:31 +02:00
apic x86/platform/UV: Add kernel parameter to set memory block size 2018-06-21 16:14:46 +02:00
cpu x86/speculation: Support Enhanced IBRS on future CPUs 2018-08-03 12:50:34 +02:00
fpu Merge commit 'upstream-x86-entry' into WIP.x86/mm 2017-12-17 12:58:53 +01:00
kprobes kprobes/x86: Prohibit probing on exception masking instructions 2018-05-13 19:52:55 +02:00
.gitignore
alternative.c x86/paravirt: Remove 'noreplace-paravirt' cmdline option 2018-01-31 10:37:45 +01:00
amd_gart_64.c x86/dma/amd_gart: Use dma_direct_{alloc,free}() 2018-03-20 10:01:57 +01:00
amd_nb.c x86/amd_nb: Add support for Raven Ridge CPUs 2018-05-13 09:00:27 -07:00
apb_timer.c Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2016-12-25 14:30:04 -08:00
aperture_64.c x86/gart: Exclude GART aperture from vmcore 2018-01-11 15:09:24 +01:00
apm_32.c x86/apm: Don't access __preempt_count with zeroed fs 2018-07-16 17:59:57 +02:00
asm-offsets_32.c x86/entry/32: Load task stack from x86_tss.sp1 in SYSENTER handler 2018-07-20 01:11:36 +02:00
asm-offsets_64.c x86/asm-offsets: Move TSS_sp0 and TSS_sp1 to asm-offsets.c 2018-07-20 01:11:35 +02:00
asm-offsets.c x86/entry/32: Enter the kernel via trampoline stack 2018-07-20 01:11:37 +02:00
audit_64.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
bootflag.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
check.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
cpuid.c x86/cpuid: Allow cpuid_read() to schedule 2018-03-27 12:01:48 +02:00
crash_dump_32.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
crash_dump_64.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
crash.c kexec_file, x86: move re-factored code to generic side 2018-04-13 17:10:27 -07:00
devicetree.c Merge branch 'x86-platform-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-04-02 16:15:32 -07:00
doublefault.c x86/entry: Fix assumptions that the HW TSS is at the beginning of cpu_tss 2017-12-17 13:59:55 +01:00
dumpstack_32.c x86/dumpstack: Unify show_regs() 2018-03-08 12:04:59 +01:00
dumpstack_64.c x86/dumpstack: Unify show_regs() 2018-03-08 12:04:59 +01:00
dumpstack.c x86/dumpstack: Explain the reasoning for the prologue and buffer size 2018-04-26 16:15:28 +02:00
e820.c x86/e820: put !E820_TYPE_RAM regions into memblock.reserved 2018-06-28 11:16:44 -07:00
early_printk.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
early-quirks.c x86/early-quirks: Rename duplicate define of dev_err 2018-05-13 20:04:35 +02:00
ebda.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
eisa.c x86/eisa: Add missing include 2017-08-31 21:34:48 +02:00
espfix_64.c x86/espfix: Document use of _PAGE_GLOBAL 2018-04-09 18:27:33 +02:00
ftrace_32.S x86/retpoline/ftrace: Convert ftrace assembler indirect jumps 2018-01-12 00:14:30 +01:00
ftrace_64.S Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-01-28 12:19:23 -08:00
ftrace.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
head32.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
head64.c Revert "x86/mm: Mark __pgtable_l5_enabled __initdata" 2018-06-23 14:20:37 +02:00
head_32.S x86/pgtable/32: Allocate 8k page-tables when PTI is enabled 2018-07-20 01:11:41 +02:00
head_64.S x86/mm: Comment _PAGE_GLOBAL mystery 2018-04-12 09:05:58 +02:00
hpet.c treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
hw_breakpoint.c
i8237.c x86/i8237: Register device based on FADT legacy boot flag 2018-04-27 16:44:29 +02:00
i8253.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
i8259.c Merge branch 'linus' into x86/apic, to resolve conflicts 2017-11-07 10:51:10 +01:00
idt.c x86/idt: Simplify the idt_setup_apic_and_irq_gates() 2018-06-06 13:38:01 +02:00
io_delay.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
ioport.c x86/ioport: add ksys_ioperm() helper; remove in-kernel calls to sys_ioperm() 2018-04-02 20:16:12 +02:00
irq_32.c x86/retpoline/irq32: Convert assembler indirect jumps 2018-01-12 00:14:32 +01:00
irq_64.c x86/irq/64: Print the offending IP in the stack overflow warning 2017-12-17 13:59:53 +01:00
irq_work.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
irq.c Drivers: hv: vmbus: Implement Direct Mode for stimer0 2018-03-06 09:57:17 -08:00
irqflags.S x86/paravirt: Make native_save_fl() extern inline 2018-07-03 10:56:27 +02:00
irqinit.c x86/apic: Simplify init_bsp_APIC() usage 2018-02-13 17:30:38 +01:00
itmt.c x86/headers: Remove duplicate #includes 2017-12-12 11:32:24 +01:00
jailhouse.c x86: Convert x86_platform_ops to timespec64 2018-05-19 14:03:14 +02:00
jump_label.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
kdebugfs.c x86, mpparse, x86/acpi, x86/PCI, x86/dmi, SFI: Use memremap() for RAM mappings 2017-07-18 11:37:58 +02:00
kexec-bzimage64.c kexec_file: do not add extra alignment to efi memmap 2018-04-20 17:18:36 -07:00
kgdb.c
ksysfs.c treewide: kmalloc() -> kmalloc_array() 2018-06-12 16:19:22 -07:00
kvm.c kvm: rename KVM_HINTS_DEDICATED to KVM_HINTS_REALTIME 2018-05-17 19:12:13 +02:00
kvmclock.c x86: Convert x86_platform_ops to timespec64 2018-05-19 14:03:14 +02:00
ldt.c x86/ldt: Enable LDT user-mapping for PAE 2018-07-20 01:11:48 +02:00
livepatch.c
machine_kexec_32.c x86/kexec: Allocate 8k PGDs for PTI 2018-07-30 13:53:48 +02:00
machine_kexec_64.c x86/mm: Stop pretending pgtable_l5_enabled is a variable 2018-05-19 11:56:57 +02:00
Makefile x86/paravirt: Make native_save_fl() extern inline 2018-07-03 10:56:27 +02:00
mmconf-fam10h_64.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
module.c x86: Treat R_X86_64_PLT32 as R_X86_64_PC32 2018-02-22 09:01:10 -08:00
mpparse.c Merge branch 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-02-14 17:02:15 -08:00
msr.c x86/msr: Remove bogus cleanup from the error path 2016-12-25 10:47:41 +01:00
nmi_selftest.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
nmi.c locking/atomics: COCCINELLE/treewide: Convert trivial ACCESS_ONCE() patterns to READ_ONCE()/WRITE_ONCE() 2017-10-25 11:01:08 +02:00
paravirt_patch_32.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
paravirt_patch_64.c x86/paravirt: Dont patch flush_tlb_single 2017-12-17 14:27:52 +01:00
paravirt-spinlocks.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
paravirt.c x86/mm: Rename flush_tlb_single() and flush_tlb_one() to __flush_tlb_one_[user|kernel]() 2018-02-15 01:15:52 +01:00
pci-calgary_64.c x86/dma: Remove dma_alloc_coherent_gfp_flags() 2018-03-20 10:01:58 +01:00
pci-dma.c x86/pci-dma: switch the VIA 32-bit DMA quirk to use the struct device flag 2018-05-28 12:48:25 +02:00
pci-iommu_table.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
pci-swiotlb.c x86/dma: Use generic swiotlb_ops 2018-03-20 10:01:57 +01:00
pcspeaker.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
perf_regs.c perf/x86: Store user space frame-pointer value on a sample 2018-05-25 08:11:12 +02:00
platform-quirks.c x86/i8237: Register device based on FADT legacy boot flag 2018-04-27 16:44:29 +02:00
pmem.c resource: Provide resource struct in resource walk callback 2017-11-07 15:35:57 +01:00
probe_roms.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
process_32.c x86/entry: Rename update_sp0 to update_task_stack 2018-07-20 01:11:40 +02:00
process_64.c x86/entry: Rename update_sp0 to update_task_stack 2018-07-20 01:11:40 +02:00
process.c x86/entry/32: Enter the kernel via trampoline stack 2018-07-20 01:11:37 +02:00
ptrace.c signal: Ensure every siginfo we send has all bits initialized 2018-04-25 10:40:51 -05:00
pvclock.c x86: Convert x86_platform_ops to timespec64 2018-05-19 14:03:14 +02:00
quirks.c x86/mce: Check for alternate indication of machine check recovery on Skylake 2018-06-07 22:22:12 +02:00
reboot_fixups_32.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
reboot.c x86/apic: Fix restoring boot IRQ mode in reboot and kexec/kdump 2018-02-17 11:47:45 +01:00
relocate_kernel_32.S
relocate_kernel_64.S x86/kexec: Make kexec (mostly) work in 5-level paging mode 2018-01-31 08:39:40 +01:00
resource.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
rtc.c x86: Convert x86_platform_ops to timespec64 2018-05-19 14:03:14 +02:00
setup_percpu.c x86/cpu_entry_area: Sync cpu_entry_area to initial_page_table 2018-03-01 09:48:27 +01:00
setup.c mm/pkeys, x86, powerpc: Display pkey in smaps if arch supports pkeys 2018-05-09 11:51:49 +10:00
signal_compat.c signal: Add TRAP_UNK si_code for undiagnosted trap exceptions 2018-04-25 10:40:56 -05:00
signal.c rseq: Avoid infinite recursion when delivering SIGSEGV 2018-06-22 19:04:22 +02:00
smp.c x86/tracing: Disentangle pagefault and resched IPI tracing key 2017-08-29 11:42:29 +02:00
smpboot.c x86/mm/32: Initialize the CR4 shadow before __flush_tlb_all() 2018-07-03 09:26:10 +02:00
stacktrace.c Merge branch 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-01-03 16:41:07 -08:00
step.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
sys_x86_64.c compat: Move compat_timespec/ timeval to compat_time.h 2018-04-19 13:29:54 +02:00
sysfb_efi.c
sysfb_simplefb.c
sysfb.c
tboot.c x86/pti: Make unpoison of pgd for trusted boot work for real 2018-01-11 23:36:59 +01:00
tce_64.c
time.c x86/time: Unconditionally register legacy timer interrupt 2018-01-14 20:18:23 +01:00
tls.c x86/ldt: Make the LDT mapping RO 2017-12-23 21:13:01 +01:00
tls.h
topology.c
trace_clock.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
tracepoint.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
traps.c Merge branch 'linus' into x86/urgent 2018-06-22 21:20:35 +02:00
tsc_msr.c
tsc_sync.c Merge branch 'x86-timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-11-13 19:07:38 -08:00
tsc.c x86/tsc: Fix mark_tsc_unstable() 2018-05-02 16:10:40 +02:00
umip.c signal: Ensure every siginfo we send has all bits initialized 2018-04-25 10:40:51 -05:00
unwind_frame.c x86/unwind: Disable unwinder warnings on 32-bit 2017-10-10 12:49:49 +02:00
unwind_guess.c x86/unwind: Add the ORC unwinder 2017-07-26 13:18:20 +02:00
unwind_orc.c extable: Make init_kernel_text() global 2018-02-21 16:54:06 +01:00
uprobes.c uprobes/x86: Remove incorrect WARN_ON() in uprobe_init_insn() 2018-06-21 17:11:02 +02:00
verify_cpu.S x86/boot: Annotate verify_cpu() as a callable function 2017-09-28 09:39:03 +02:00
vm86_32.c x86/entry: Rename update_sp0 to update_task_stack 2018-07-20 01:11:40 +02:00
vmlinux.lds.S x86/mm/pti: Make pti_clone_kernel_text() compile on 32 bit 2018-07-20 01:11:44 +02:00
vsmp_64.c x86/apic: Remove unused callbacks 2017-09-25 20:51:58 +02:00
x86_init.c xen, mm: allow deferred page initialization for xen pv domains 2018-04-11 10:28:38 -07:00