The mm_struct contains a function pointer *get_unmapped_area(), which is
set to either arch_get_unmapped_area() or arch_get_unmapped_area_topdown()
during the initialization of the mm.
Since the function pointer only ever points to two functions that are
named the same across all arch's, a function pointer is not really
required. In addition future changes will want to add versions of the
functions that take additional arguments. So to save a pointers worth of
bytes in mm_struct, and prevent adding additional function pointers to
mm_struct in future changes, remove it and keep the information about
which get_unmapped_area() to use in a flag.
Add the new flag to MMF_INIT_MASK so it doesn't get clobbered on fork by
mmf_init_flags(). Most MM flags get clobbered on fork. In the
pre-existing behavior mm->get_unmapped_area() would get copied to the new
mm in dup_mm(), so not clobbering the flag preserves the existing behavior
around inheriting the topdown-ness.
Introduce a helper, mm_get_unmapped_area(), to easily convert code that
refers to the old function pointer to instead select and call either
arch_get_unmapped_area() or arch_get_unmapped_area_topdown() based on the
flag. Then drop the mm->get_unmapped_area() function pointer. Leave the
get_unmapped_area() pointer in struct file_operations alone. The main
purpose of this change is to reorganize in preparation for future changes,
but it also converts the calls of mm->get_unmapped_area() from indirect
branches into a direct ones.
The stress-ng bigheap benchmark calls realloc a lot, which calls through
get_unmapped_area() in the kernel. On x86, the change yielded a ~1%
improvement there on a retpoline config.
In testing a few x86 configs, removing the pointer unfortunately didn't
result in any actual size reductions in the compiled layout of mm_struct.
But depending on compiler or arch alignment requirements, the change could
shrink the size of mm_struct.
Link: https://lkml.kernel.org/r/20240326021656.202649-3-rick.p.edgecombe@intel.com
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Aneesh Kumar K.V <aneesh.kumar@kernel.org>
Cc: Borislav Petkov (AMD) <bp@alien8.de>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Deepak Gupta <debug@rivosinc.com>
Cc: Guo Ren <guoren@kernel.org>
Cc: Helge Deller <deller@gmx.de>
Cc: H. Peter Anvin (Intel) <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Naveen N. Rao <naveen.n.rao@linux.ibm.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "mm/mm_init.c: refactor free_area_init_core()".
In function free_area_init_core(), the code calculating
zone->managed_pages and the subtracting dma_reserve from DMA zone looks
very confusing.
From git history, the code calculating zone->managed_pages was for
zone->present_pages originally. The early rough assignment is for
optimize zone's pcp and water mark setting. Later, managed_pages was
introduced into zone to represent the number of managed pages by buddy.
Now, zone->managed_pages is zeroed out and reset in mem_init() when
calling memblock_free_all(). zone's pcp and wmark setting relying on
actual zone->managed_pages are done later than mem_init() invocation. So
we don't need rush to early calculate and set zone->managed_pages, just
set it as zone->present_pages, will adjust it in mem_init().
And also add a new function calc_nr_kernel_pages() to count up free but
not reserved pages in memblock, then assign it to nr_all_pages and
nr_kernel_pages after memmap pages are allocated.
This patch (of 6):
Variable dma_reserve and its usage was introduced in commit 0e0b864e06
("[PATCH] Account for memmap and optionally the kernel image as holes").
Its original purpose was to accounting for the reserved pages in DMA zone
to make DMA zone's watermarks calculation more accurate on x86.
However, currently there's zone->managed_pages to account for all
available pages for buddy, zone->present_pages to account for all present
physical pages in zone. What is more important, on x86, calculating and
setting the zone->managed_pages is a temporary move, all zone's
managed_pages will be zeroed out and reset to the actual value according
to how many pages are added to buddy allocator in mem_init(). Before
mem_init(), no buddy alloction is requested. And zone's pcp and watermark
setting are all done after mem_init(). So, no need to worry about the DMA
zone's setting accuracy during free_area_init().
Hence, remove memblock_find_dma_reserve() to stop calculating and
setting dma_reserve.
Link: https://lkml.kernel.org/r/20240325145646.1044760-1-bhe@redhat.com
Link: https://lkml.kernel.org/r/20240325145646.1044760-2-bhe@redhat.com
Signed-off-by: Baoquan He <bhe@redhat.com>
Reviewed-by: Mike Rapoport (IBM) <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
cpu_feature_enabled(X86_FEATURE_OSPKE) does not necessarily reflect
whether CR4.PKE is set on the CPU. In particular, they may differ on
non-BSP CPUs before setup_pku() is executed. In this scenario, RDPKRU
will #UD causing the system to hang.
Fix by checking CR4 for PKE enablement which is always correct for the
current CPU.
The scenario happens by inserting a WARN* before setup_pku() in
identiy_cpu() or some other diagnostic which would lead to calling
__show_regs().
[ bp: Massage commit message. ]
Signed-off-by: David Kaplan <david.kaplan@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20240421191728.32239-1-bp@kernel.org
In our production environment, after removing monitor groups, those
unused RMIDs get stuck in the limbo list forever because their
llc_occupancy is always larger than the threshold. But the unused RMIDs
can be successfully freed by turning up the threshold.
In order to know how much the threshold should be, perf can be used to
acquire the llc_occupancy of RMIDs in each rdt domain.
Instead of using perf tool to track llc_occupancy and filter the log
manually, it is more convenient for users to use tracepoint to do this
work. So add a new tracepoint that shows the llc_occupancy of busy RMIDs
when scanning the limbo list.
Suggested-by: Reinette Chatre <reinette.chatre@intel.com>
Suggested-by: James Morse <james.morse@arm.com>
Signed-off-by: Haifeng Xu <haifeng.xu@shopee.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: James Morse <james.morse@arm.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Link: https://lore.kernel.org/r/20240408092303.26413-3-haifeng.xu@shopee.com
Now only the pseudo-locking part uses tracepoints to do event tracking,
but other parts of resctrl may need new tracepoints. It is unnecessary
to create separate header files and define CREATE_TRACE_POINTS in
different c files which fragments the resctrl tracing.
Therefore, give the resctrl tracepoint header file a generic name to
support its use for tracepoints that are not specific to pseudo-locking.
No functional change.
Suggested-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Haifeng Xu <haifeng.xu@shopee.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Link: https://lore.kernel.org/r/20240408092303.26413-2-haifeng.xu@shopee.com
The per-resource MSR update functions cat_wrmsr(), mba_wrmsr_intel(),
and mba_wrmsr_amd() all take three arguments:
(struct rdt_domain *d, struct msr_param *m, struct rdt_resource *r)
struct msr_param contains pointers to both struct rdt_resource and struct
rdt_domain, thus only struct msr_param is necessary.
Pass struct msr_param as a single parameter. Clean up formatting and
fix some fir tree declaration ordering.
No functional change.
Suggested-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Reviewed-by: Babu Moger <babu.moger@amd.com>
Tested-by: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com>
Link: https://lore.kernel.org/r/20240308213846.77075-3-tony.luck@intel.com
reset_all_ctrls() and resctrl_arch_update_domains() use on_each_cpu_mask()
to call rdt_ctrl_update() on potentially one CPU from each domain.
But this means rdt_ctrl_update() needs to figure out which domain to
apply changes to. Doing so requires a search of all domains in a resource,
which can only be done safely if cpus_lock is held. Both callers do hold
this lock, but there isn't a way for a function called on another CPU
via IPI to verify this.
Commit
c0d848fcb0 ("x86/resctrl: Remove lockdep annotation that triggers
false positive")
removed the incorrect assertions.
Add the target domain to the msr_param structure and call
rdt_ctrl_update() for each domain separately using
smp_call_function_single(). This means that rdt_ctrl_update() doesn't
need to search for the domain and get_domain_from_cpu() can safely
assert that the cpus_lock is held since the remaining callers do not use
IPI.
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Reviewed-by: James Morse <james.morse@arm.com>
Reviewed-by: Babu Moger <babu.moger@amd.com>
Tested-by: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com>
Link: https://lore.kernel.org/r/20240308213846.77075-2-tony.luck@intel.com
Commit a72bbec70d ("crash: hotplug support for kexec_load()")
introduced a new kexec flag, `KEXEC_UPDATE_ELFCOREHDR`. Kexec tool uses
this flag to indicate to the kernel that it is safe to modify the
elfcorehdr of the kdump image loaded using the kexec_load system call.
However, it is possible that architectures may need to update kexec
segments other then elfcorehdr. For example, FDT (Flatten Device Tree)
on PowerPC. Introducing a new kexec flag for every new kexec segment
may not be a good solution. Hence, a generic kexec flag bit,
`KEXEC_CRASH_HOTPLUG_SUPPORT`, is introduced to share the CPU/Memory
hotplug support intent between the kexec tool and the kernel for the
kexec_load system call.
Now we have two kexec flags that enables crash hotplug support for
kexec_load system call. First is KEXEC_UPDATE_ELFCOREHDR (only used in
x86), and second is KEXEC_CRASH_HOTPLUG_SUPPORT (for all architectures).
To simplify the process of finding and reporting the crash hotplug
support the following changes are introduced.
1. Define arch specific function to process the kexec flags and
determine crash hotplug support
2. Rename the @update_elfcorehdr member of struct kimage to
@hotplug_support and populate it for both kexec_load and
kexec_file_load syscalls, because architecture can update more than
one kexec segment
3. Let generic function crash_check_hotplug_support report hotplug
support for loaded kdump image based on value of @hotplug_support
To bring the x86 crash hotplug support in line with the above points,
the following changes have been made:
- Introduce the arch_crash_hotplug_support function to process kexec
flags and determine crash hotplug support
- Remove the arch_crash_hotplug_[cpu|memory]_support functions
Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com>
Acked-by: Baoquan He <bhe@redhat.com>
Acked-by: Hari Bathini <hbathini@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240326055413.186534-3-sourabhjain@linux.ibm.com
In the event of memory hotplug or online/offline events, the crash
memory hotplug notifier `crash_memhp_notifier()` receives a
`memory_notify` object but doesn't forward that object to the
generic and architecture-specific crash hotplug handler.
The `memory_notify` object contains the starting PFN (Page Frame Number)
and the number of pages in the hot-removed memory. This information is
necessary for architectures like PowerPC to update/recreate the kdump
image, specifically `elfcorehdr`.
So update the function signature of `crash_handle_hotplug_event()` and
`arch_crash_handle_hotplug_event()` to accept the `memory_notify` object
as an argument from crash memory hotplug notifier.
Since no such object is available in the case of CPU hotplug event, the
crash CPU hotplug notifier `crash_cpuhp_online()` passes NULL to the
crash hotplug handler.
Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com>
Acked-by: Baoquan He <bhe@redhat.com>
Acked-by: Hari Bathini <hbathini@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240326055413.186534-2-sourabhjain@linux.ibm.com
Fix cpuid_deps[] to list the correct dependencies for GFNI, VAES, and
VPCLMULQDQ. These features don't depend on AVX512, and there exist CPUs
that support these features but not AVX512. GFNI actually doesn't even
depend on AVX.
This prevents GFNI from being unnecessarily disabled if AVX is disabled
to mitigate the GDS vulnerability.
This also prevents all three features from being unnecessarily disabled
if AVX512VL (or its dependency AVX512F) were to be disabled, but it
looks like there isn't any case where this happens anyway.
Fixes: c128dbfa0f ("x86/cpufeatures: Enable new SSE/AVX/AVX512 CPU features")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/r/20240417060434.47101-1-ebiggers@kernel.org
There's a new conflict between this commit pending in x86/cpu:
63edbaa48a x86/cpu/topology: Add support for the AMD 0x80000026 leaf
And these fixes in x86/urgent:
c064b536a8 x86/cpu/amd: Make the NODEID_MSR union actually work
1b3108f689 x86/cpu/amd: Make the CPUID 0x80000008 parser correct
Resolve them.
Conflicts:
arch/x86/kernel/cpu/topology_amd.c
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The topology rework missed that early_init_amd() tries to re-enable the
Topology Extensions when the BIOS disabled them.
The new parser is invoked before early_init_amd() so the re-enable attempt
happens too late.
Move it into the AMD specific topology parser code where it belongs.
Fixes: f7fb3b2dd9 ("x86/cpu: Provide an AMD/HYGON specific topology parser")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/878r1j260l.ffs@tglx
A system with NODEID_MSR was reported to crash during early boot without
any output.
The reason is that the union which is used for accessing the bitfields in
the MSR is written wrongly and the resulting executable code accesses the
wrong part of the MSR data.
As a consequence a later division by that value results in 0 and that
result is used for another division as divisor, which obviously does not
work well.
The magic world of C, unions and bitfields:
union {
u64 bita : 3,
bitb : 3;
u64 all;
} x;
x.all = foo();
a = x.bita;
b = x.bitb;
results in the effective executable code of:
a = b = x.bita;
because bita and bitb are treated as union members and therefore both end
up at bit offset 0.
Wrapping the bitfield into an anonymous struct:
union {
struct {
u64 bita : 3,
bitb : 3;
};
u64 all;
} x;
works like expected.
Rework the NODEID_MSR union in exactly that way to cure the problem.
Fixes: f7fb3b2dd9 ("x86/cpu: Provide an AMD/HYGON specific topology parser")
Reported-by: "kernelci.org bot" <bot@kernelci.org>
Reported-by: Laura Nao <laura.nao@collabora.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Laura Nao <laura.nao@collabora.com>
Link: https://lore.kernel.org/r/20240410194311.596282919@linutronix.de
Closes: https://lore.kernel.org/all/20240322175210.124416-1-laura.nao@collabora.com/
CPUID 0x80000008 ECX.cpu_nthreads describes the number of threads in the
package. The parser uses this value to initialize the SMT domain level.
That's wrong because cpu_nthreads does not describe the number of threads
per physical core. So this needs to set the CORE domain level and let the
later parsers set the SMT shift if available.
Preset the SMT domain level with the assumption of one thread per core,
which is correct ifrt here are no other CPUID leafs to parse, and propagate
cpu_nthreads and the core level APIC bitwidth into the CORE domain.
Fixes: f7fb3b2dd9 ("x86/cpu: Provide an AMD/HYGON specific topology parser")
Reported-by: "kernelci.org bot" <bot@kernelci.org>
Reported-by: Laura Nao <laura.nao@collabora.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Laura Nao <laura.nao@collabora.com>
Link: https://lore.kernel.org/r/20240410194311.535206450@linutronix.de
SEV-ES allows passing custom contents for x87, SSE and AVX state into the VMSA.
Allow userspace to do that with the usual KVM_SET_XSAVE API and only mark
FPU contents as confidential after it has been copied and encrypted into
the VMSA.
Since the XSAVE state for AVX is the first, it does not need the
compacted-state handling of get_xsave_addr(). However, there are other
parts of XSAVE state in the VMSA that currently are not handled, and
the validation logic of get_xsave_addr() is pointless to duplicate
in KVM, so move get_xsave_addr() to public FPU API; it is really just
a facility to operate on XSAVE state and does not expose any internal
details of arch/x86/kernel/fpu.
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20240404121327.3107131-12-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
So we are using the 'ia32_cap' value in a number of places,
which got its name from MSR_IA32_ARCH_CAPABILITIES MSR register.
But there's very little 'IA32' about it - this isn't 32-bit only
code, nor does it originate from there, it's just a historic
quirk that many Intel MSR names are prefixed with IA32_.
This is already clear from the helper method around the MSR:
x86_read_arch_cap_msr(), which doesn't have the IA32 prefix.
So rename 'ia32_cap' to 'x86_arch_cap_msr' to be consistent with
its role and with the naming of the helper function.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Nikolay Borisov <nik.borisov@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/9592a18a814368e75f8f4b9d74d3883aa4fd1eaf.1712813475.git.jpoimboe@kernel.org
topo_set_cpuids() updates cpu_present_map and cpu_possible map. It is
invoked during enumeration and "physical hotplug" operations. In the
latter case this results in a kernel crash because cpu_possible_map is
marked read only after init completes.
There is no reason to update cpu_possible_map in that function. During
enumeration cpu_possible_map is not relevant and gets fully initialized
after enumeration completed. On "physical hotplug" the bit is already set
because the kernel allows only CPUs to be plugged which have been
enumerated and associated to a CPU number during early boot.
Remove the bogus update of cpu_possible_map.
Fixes: 0e53e7b656 ("x86/cpu/topology: Sanitize the APIC admission logic")
Reported-by: Jonathan Cameron <Jonathan.Cameron@Huawei.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/87ttkc6kwx.ffs@tglx
In smp_prepare_cpus_common() and x2apic_prepare_cpu():
- use 'cpu' instead of 'i'
- use 'node' instead of 'n'
- use vertical alignment to improve readability
- better structure basic blocks
- reduce col80 checkpatch damage
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: linux-kernel@vger.kernel.org
There's no need to carve out bits of the NOP optimization functionality
and look at JMP opcodes - simply do one more NOPs optimization pass
at the end of patching.
A lot simpler code.
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20240130105941.19707-3-bp@alien8.de
Instead of optimizing NOPs in-place, use a temporary buffer like the
usual alternatives patching flow does. This obviates the need to grab
locks when patching, see
6778977590 ("x86/alternatives: Disable interrupts and sync when optimizing NOPs in place")
While at it, add nomenclature definitions clarifying and simplifying the
naming of function-local variables in the alternatives code.
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20240130105941.19707-2-bp@alien8.de
Machine check SMIs (MSMI) signaled during SEAM operation (typically
inside TDX guests), on a system with Intel eMCA enabled, might eventually
be reported to the kernel #MC handler with the saved RIP on the stack
pointing to the instruction in kernel code after the SEAMCALL instruction
that entered the SEAM operation. Linux currently says that is a fatal
error and shuts down.
There is a new bit in IA32_MCG_STATUS that, when set to 1, indicates
that the machine check didn't originally occur at that saved RIP, but
during SEAM non-root operation.
Add new entries to the severity table to detect this for both data load
and instruction fetch that set the severity to "AR" (action required).
Increase the width of the mcgmask/mcgres fields in "struct severity"
from unsigned char to unsigned short since the new bit is in position 12.
Action required for these errors is just mark the page as poisoned and
return from the machine check handler.
HW ABI notes:
=============
The SEAM_NR bit in IA32_MCG_STATUS hasn't yet made it into the Intel
Software Developers' Manual. But it is described in section 16.5.2
of "Intel(R) Trust Domain Extensions (Intel(R) TDX) Module Base
Architecture Specification" downloadable from:
https://cdrdv2.intel.com/v1/dl/getContent/733575
Backport notes:
===============
Little value in backporting this patch to stable or LTS kernels as
this is only relevant with support for TDX, which I assume won't be
backported. But for anyone taking this to v6.1 or older, you also
need commit:
a51cbd0d86 ("x86/mce: Use severity table to handle uncorrected errors in kernel")
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20240408180944.44638-1-tony.luck@intel.com
Pull x86 mitigations from Thomas Gleixner:
"Mitigations for the native BHI hardware vulnerabilty:
Branch History Injection (BHI) attacks may allow a malicious
application to influence indirect branch prediction in kernel by
poisoning the branch history. eIBRS isolates indirect branch targets
in ring0. The BHB can still influence the choice of indirect branch
predictor entry, and although branch predictor entries are isolated
between modes when eIBRS is enabled, the BHB itself is not isolated
between modes.
Add mitigations against it either with the help of microcode or with
software sequences for the affected CPUs"
[ This also ends up enabling the full mitigation by default despite the
system call hardening, because apparently there are other indirect
calls that are still sufficiently reachable, and the 'auto' case just
isn't hardened enough.
We'll have some more inevitable tweaking in the future - Linus ]
* tag 'nativebhi' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
KVM: x86: Add BHI_NO
x86/bhi: Mitigate KVM by default
x86/bhi: Add BHI mitigation knob
x86/bhi: Enumerate Branch History Injection (BHI) bug
x86/bhi: Define SPEC_CTRL_BHI_DIS_S
x86/bhi: Add support for clearing branch history at syscall entry
x86/syscall: Don't force use of indirect calls for system calls
x86/bugs: Change commas to semicolons in 'spectre_v2' sysfs file
BHI mitigation mode spectre_bhi=auto does not deploy the software
mitigation by default. In a cloud environment, it is a likely scenario
where userspace is trusted but the guests are not trusted. Deploying
system wide mitigation in such cases is not desirable.
Update the auto mode to unconditionally mitigate against malicious
guests. Deploy the software sequence at VMexit in auto mode also, when
hardware mitigation is not available. Unlike the force =on mode,
software sequence is not deployed at syscalls in auto mode.
Suggested-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Daniel Sneddon <daniel.sneddon@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
