Christian reported that commit a430c11f4015 ("intel_idle: Rescan "dead" SMT
siblings during initialization") broke the use case in which both 'nosmt'
and 'maxcpus' are on the kernel command line because it onlines primary
threads, which were offline due to the maxcpus limit.

The initially proposed fix to skip primary threads in the loop is
inconsistent. While it prevents the primary thread to be onlined, it then
onlines the corresponding hyperthread(s), which does not really make sense.

The CPU iterator in cpuhp_smt_enable() contains a check which excludes all
threads of a core, when the primary thread is offline. The default
implementation is a NOOP and therefore not effective on x86.

Implement topology_is_core_online() on x86 to address this issue. This
makes the behaviour consistent between x86 and PowerPC.

Fixes: a430c11f4015 ("intel_idle: Rescan "dead" SMT siblings during initialization")
Fixes: f694481b1d31 ("ACPI: processor: Rescan "dead" SMT siblings during initialization")
Closes: https://lore.kernel.org/linux-pm/724616a2-6374-4ba3-8ce3-ea9c45e2ae3b@arm.com/
Reported-by: Christian Loehle <christian.loehle@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Rafael J. Wysocki (Intel) <rafael@kernel.org>
Tested-by: Christian Loehle <christian.loehle@arm.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/12740505.O9o76ZdvQC@rafael.j.wysocki

The sev_evict_cache() is guest-related code and should be guarded by
CONFIG_AMD_MEM_ENCRYPT, not CONFIG_KVM_AMD_SEV.

CONFIG_AMD_MEM_ENCRYPT=y is required for a guest to run properly as an SEV-SNP
guest, but a guest kernel built with CONFIG_KVM_AMD_SEV=n would get the stub
function of sev_evict_cache() instead of the version that performs the actual
eviction. Move the function declarations under the appropriate #ifdef.

Fixes: 7b306dfa326f ("x86/sev: Evict cache lines during SNP memory validation")
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: stable@kernel.org # 6.16.x
Link: https://lore.kernel.org/r/70e38f2c4a549063de54052c9f64929705313526.1757708959.git.thomas.lendacky@amd.com

Pull vmescape mitigation fixes from Dave Hansen:
 "Mitigate vmscape issue with indirect branch predictor flushes.

  vmscape is a vulnerability that essentially takes Spectre-v2 and
  attacks host userspace from a guest. It particularly affects
  hypervisors like QEMU.

  Even if a hypervisor may not have any sensitive data like disk
  encryption keys, guest-userspace may be able to attack the
  guest-kernel using the hypervisor as a confused deputy.

  There are many ways to mitigate vmscape using the existing Spectre-v2
  defenses like IBRS variants or the IBPB flushes. This series focuses
  solely on IBPB because it works universally across vendors and all
  vulnerable processors. Further work doing vendor and model-specific
  optimizations can build on top of this if needed / wanted.

  Do the normal issue mitigation dance:

   - Add the CPU bug boilerplate

   - Add a list of vulnerable CPUs

   - Use IBPB to flush the branch predictors after running guests"

* tag 'vmscape-for-linus-20250904' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/vmscape: Add old Intel CPUs to affected list
  x86/vmscape: Warn when STIBP is disabled with SMT
  x86/bugs: Move cpu_bugs_smt_update() down
  x86/vmscape: Enable the mitigation
  x86/vmscape: Add conditional IBPB mitigation
  x86/vmscape: Enumerate VMSCAPE bug
  Documentation/hw-vuln: Add VMSCAPE documentation

Define ARCH_PAGE_TABLE_SYNC_MASK and arch_sync_kernel_mappings() to ensure
page tables are properly synchronized when calling p*d_populate_kernel().

For 5-level paging, synchronization is performed via
pgd_populate_kernel().  In 4-level paging, pgd_populate() is a no-op, so
synchronization is instead performed at the P4D level via
p4d_populate_kernel().

This fixes intermittent boot failures on systems using 4-level paging and
a large amount of persistent memory:

  BUG: unable to handle page fault for address: ffffe70000000034
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  PGD 0 P4D 0
  Oops: 0002 [#1] SMP NOPTI
  RIP: 0010:__init_single_page+0x9/0x6d
  Call Trace:
   <TASK>
   __init_zone_device_page+0x17/0x5d
   memmap_init_zone_device+0x154/0x1bb
   pagemap_range+0x2e0/0x40f
   memremap_pages+0x10b/0x2f0
   devm_memremap_pages+0x1e/0x60
   dev_dax_probe+0xce/0x2ec [device_dax]
   dax_bus_probe+0x6d/0xc9
   [... snip ...]
   </TASK>

It also fixes a crash in vmemmap_set_pmd() caused by accessing vmemmap
before sync_global_pgds() [1]:

  BUG: unable to handle page fault for address: ffffeb3ff1200000
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  PGD 0 P4D 0
  Oops: Oops: 0002 [#1] PREEMPT SMP NOPTI
  Tainted: [W]=WARN
  RIP: 0010:vmemmap_set_pmd+0xff/0x230
   <TASK>
   vmemmap_populate_hugepages+0x176/0x180
   vmemmap_populate+0x34/0x80
   __populate_section_memmap+0x41/0x90
   sparse_add_section+0x121/0x3e0
   __add_pages+0xba/0x150
   add_pages+0x1d/0x70
   memremap_pages+0x3dc/0x810
   devm_memremap_pages+0x1c/0x60
   xe_devm_add+0x8b/0x100 [xe]
   xe_tile_init_noalloc+0x6a/0x70 [xe]
   xe_device_probe+0x48c/0x740 [xe]
   [... snip ...]

Link: https://lkml.kernel.org/r/20250818020206.4517-4-harry.yoo@oracle.com
Fixes: 8d400913c231 ("x86/vmemmap: handle unpopulated sub-pmd ranges")
Signed-off-by: Harry Yoo <harry.yoo@oracle.com>
Closes: https://lore.kernel.org/linux-mm/20250311114420.240341-1-gwan-gyeong.mun@intel.com [1]
Suggested-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Kiryl Shutsemau <kas@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: bibo mao <maobibo@loongson.cn>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Christoph Lameter (Ampere) <cl@gentwo.org>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Dmitriy Vyukov <dvyukov@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jane Chu <jane.chu@oracle.com>
Cc: Joao Martins <joao.m.martins@oracle.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Thomas Huth <thuth@redhat.com>
Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Pull xen fixes from Juergen Gross:
 "Two small cleanups which are both relevant only when running as a Xen
  guest"

* tag 'for-linus-6.17-rc3-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  drivers/xen/xenbus: remove quirk for Xen 3.x
  compiler: remove __ADDRESSABLE_ASM{_STR,}() again

__ADDRESSABLE_ASM_STR() is where the necessary stringification happens.
As long as "sym" doesn't contain any odd characters, no quoting is
required for its use with .quad / .long. In fact the quotation gets in
the way with gas 2.25; it's only from 2.26 onwards that quoted symbols
are half-way properly supported.

However, assembly being different from C anyway, drop
__ADDRESSABLE_ASM_STR() and its helper macro altogether. A simple
.global directive will suffice to get the symbol "declared", i.e. into
the symbol table. While there also stop open-coding STATIC_CALL_TRAMP()
and STATIC_CALL_KEY().

Fixes: 0ef8047b737d ("x86/static-call: provide a way to do very early static-call updates")
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: stable@vger.kernel.org
Signed-off-by: Juergen Gross <jgross@suse.com>
Message-ID: <609d2c74-de13-4fae-ab1a-1ec44afb948d@suse.com>

Pull x86 fixes from Borislav Petkov:

 - Remove a transitional asm/cpuid.h header which was added only as a
   fallback during cpuid helpers reorg

 - Initialize reserved fields in the SVSM page validation calls
   structure to zero in order to allow for future structure extensions

 - Have the sev-guest driver's buffers used in encryption operations be
   in linear mapping space as the encryption operation can be offloaded
   to an accelerator

 - Have a read-only MSR write when in an AMD SNP guest trap to the
   hypervisor as it is usually done. This makes the guest user
   experience better by simply raising a #GP instead of terminating said
   guest

 - Do not output AVX512 elapsed time for kernel threads because the data
   is wrong and fix a NULL pointer dereferencing in the process

 - Adjust the SRSO mitigation selection to the new attack vectors

* tag 'x86_urgent_for_v6.17_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/cpuid: Remove transitional <asm/cpuid.h> header
  x86/sev: Ensure SVSM reserved fields in a page validation entry are initialized to zero
  virt: sev-guest: Satisfy linear mapping requirement in get_derived_key()
  x86/sev: Improve handling of writes to intercepted TSC MSRs
  x86/fpu: Fix NULL dereference in avx512_status()
  x86/bugs: Select best SRSO mitigation

All CPUID call sites were updated at commit:

    968e30006807 ("x86/cpuid: Set <asm/cpuid/api.h> as the main CPUID header")

to include <asm/cpuid/api.h> instead of <asm/cpuid.h>.

The <asm/cpuid.h> header was still retained as a wrapper, just in case
some new code in -next started using it.  Now that everything is merged
to Linus' tree, remove the header.

Signed-off-by: Ahmed S. Darwish <darwi@linutronix.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250815070227.19981-2-darwi@linutronix.de

VMSCAPE is a vulnerability that exploits insufficient branch predictor
isolation between a guest and a userspace hypervisor (like QEMU). Existing
mitigations already protect kernel/KVM from a malicious guest. Userspace
can additionally be protected by flushing the branch predictors after a
VMexit.

Since it is the userspace that consumes the poisoned branch predictors,
conditionally issue an IBPB after a VMexit and before returning to
userspace. Workloads that frequently switch between hypervisor and
userspace will incur the most overhead from the new IBPB.

This new IBPB is not integrated with the existing IBPB sites. For
instance, a task can use the existing speculation control prctl() to
get an IBPB at context switch time. With this implementation, the
IBPB is doubled up: one at context switch and another before running
userspace.

The intent is to integrate and optimize these cases post-embargo.

[ dhansen: elaborate on suboptimal IBPB solution ]

Suggested-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Sean Christopherson <seanjc@google.com>

The VMSCAPE vulnerability may allow a guest to cause Branch Target
Injection (BTI) in userspace hypervisors.

Kernels (both host and guest) have existing defenses against direct BTI
attacks from guests. There are also inter-process BTI mitigations which
prevent processes from attacking each other. However, the threat in this
case is to a userspace hypervisor within the same process as the attacker.

Userspace hypervisors have access to their own sensitive data like disk
encryption keys and also typically have access to all guest data. This
means guest userspace may use the hypervisor as a confused deputy to attack
sensitive guest kernel data. There are no existing mitigations for these
attacks.

Introduce X86_BUG_VMSCAPE for this vulnerability and set it on affected
Intel and AMD CPUs.

Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Borislav Petkov (AMD) <bp@alien8.de>