arch-independent options, each of which is an
aggregation of existing arch-specific options.
+ Note, "mitigations" is supported if and only if the
+ kernel was built with CPU_MITIGATIONS=y.
+
off
Disable all optional CPU mitigations. This
improves system performance, but it may also
retbleed=off [X86]
spec_rstack_overflow=off [X86]
spec_store_bypass_disable=off [X86,PPC]
+ spectre_bhi=off [X86]
spectre_v2_user=off [X86]
srbds=off [X86,INTEL]
ssbd=force-off [ARM64]
norid [S390] ignore the RID field and force use of
one PCI domain per PCI function
- pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
+ pcie_aspm= [PCIE] Forcibly enable or ignore PCIe Active State Power
Management.
- off Disable ASPM.
+ off Don't touch ASPM configuration at all. Leave any
+ configuration done by firmware unchanged.
force Enable ASPM even on devices that claim not to support it.
WARNING: Forcing ASPM on may cause system lockups.
prot_virt= [S390] enable hosting protected virtual machines
isolated from the hypervisor (if hardware supports
- that).
+ that). If enabled, the default kernel base address
+ might be overridden even when Kernel Address Space
+ Layout Randomization is disabled.
Format: <bool>
psi= [KNL] Enable or disable pressure stall information
sonypi.*= [HW] Sony Programmable I/O Control Device driver
See Documentation/admin-guide/laptops/sonypi.rst
+ spectre_bhi= [X86] Control mitigation of Branch History Injection
+ (BHI) vulnerability. This setting affects the
+ deployment of the HW BHI control and the SW BHB
+ clearing sequence.
+
+ on - (default) Enable the HW or SW mitigation
+ as needed.
+ off - Disable the mitigation.
+
spectre_v2= [X86,EARLY] Control mitigation of Spectre variant 2
(indirect branch speculation) vulnerability.
The default operation protects the kernel from
To turn off having tracepoints sent to printk,
echo 0 > /proc/sys/kernel/tracepoint_printk
Note, echoing 1 into this file without the
- tracepoint_printk kernel cmdline option has no effect.
+ tp_printk kernel cmdline option has no effect.
The tp_printk_stop_on_boot (see below) can also be used
to stop the printing of events to console at
}
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
- /*
- * Remove all empty zero pages from the mapping for lazy refaulting
- * - This must be called after mm->context.has_pgste is set, to avoid
- * future creation of zero pages
- * - This must be called after THP was disabled.
- *
- * mm contracts with s390, that even if mm were to remove a page table,
- * racing with the loop below and so causing pte_offset_map_lock() to fail,
- * it will never insert a page table containing empty zero pages once
- * mm_forbids_zeropage(mm) i.e. mm->context.has_pgste is set.
- */
- static int __zap_zero_pages(pmd_t *pmd, unsigned long start,
- unsigned long end, struct mm_walk *walk)
- {
- unsigned long addr;
-
- for (addr = start; addr != end; addr += PAGE_SIZE) {
- pte_t *ptep;
- spinlock_t *ptl;
-
- ptep = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
- if (!ptep)
- break;
- if (is_zero_pfn(pte_pfn(*ptep)))
- ptep_xchg_direct(walk->mm, addr, ptep, __pte(_PAGE_INVALID));
- pte_unmap_unlock(ptep, ptl);
- }
- return 0;
- }
-
- static const struct mm_walk_ops zap_zero_walk_ops = {
- .pmd_entry = __zap_zero_pages,
- .walk_lock = PGWALK_WRLOCK,
- };
-
/*
* switch on pgstes for its userspace process (for kvm)
*/
mm->context.has_pgste = 1;
/* split thp mappings and disable thp for future mappings */
thp_split_mm(mm);
- walk_page_range(mm, 0, TASK_SIZE, &zap_zero_walk_ops, NULL);
mmap_write_unlock(mm);
return 0;
}
EXPORT_SYMBOL_GPL(s390_enable_sie);
- int gmap_mark_unmergeable(void)
+ static int find_zeropage_pte_entry(pte_t *pte, unsigned long addr,
+ unsigned long end, struct mm_walk *walk)
{
+ unsigned long *found_addr = walk->private;
+
+ /* Return 1 of the page is a zeropage. */
+ if (is_zero_pfn(pte_pfn(*pte))) {
+ /*
+ * Shared zeropage in e.g., a FS DAX mapping? We cannot do the
+ * right thing and likely don't care: FAULT_FLAG_UNSHARE
+ * currently only works in COW mappings, which is also where
+ * mm_forbids_zeropage() is checked.
+ */
+ if (!is_cow_mapping(walk->vma->vm_flags))
+ return -EFAULT;
+
+ *found_addr = addr;
+ return 1;
+ }
+ return 0;
+ }
+
+ static const struct mm_walk_ops find_zeropage_ops = {
+ .pte_entry = find_zeropage_pte_entry,
+ .walk_lock = PGWALK_WRLOCK,
+ };
+
+ /*
+ * Unshare all shared zeropages, replacing them by anonymous pages. Note that
+ * we cannot simply zap all shared zeropages, because this could later
+ * trigger unexpected userfaultfd missing events.
+ *
+ * This must be called after mm->context.allow_cow_sharing was
+ * set to 0, to avoid future mappings of shared zeropages.
+ *
+ * mm contracts with s390, that even if mm were to remove a page table,
+ * and racing with walk_page_range_vma() calling pte_offset_map_lock()
+ * would fail, it will never insert a page table containing empty zero
+ * pages once mm_forbids_zeropage(mm) i.e.
+ * mm->context.allow_cow_sharing is set to 0.
+ */
+ static int __s390_unshare_zeropages(struct mm_struct *mm)
+ {
+ struct vm_area_struct *vma;
+ VMA_ITERATOR(vmi, mm, 0);
+ unsigned long addr;
+ vm_fault_t fault;
+ int rc;
+
+ for_each_vma(vmi, vma) {
+ /*
+ * We could only look at COW mappings, but it's more future
+ * proof to catch unexpected zeropages in other mappings and
+ * fail.
+ */
+ if ((vma->vm_flags & VM_PFNMAP) || is_vm_hugetlb_page(vma))
+ continue;
+ addr = vma->vm_start;
+
+ retry:
+ rc = walk_page_range_vma(vma, addr, vma->vm_end,
+ &find_zeropage_ops, &addr);
+ if (rc < 0)
+ return rc;
+ else if (!rc)
+ continue;
+
+ /* addr was updated by find_zeropage_pte_entry() */
+ fault = handle_mm_fault(vma, addr,
+ FAULT_FLAG_UNSHARE | FAULT_FLAG_REMOTE,
+ NULL);
+ if (fault & VM_FAULT_OOM)
+ return -ENOMEM;
+ /*
+ * See break_ksm(): even after handle_mm_fault() returned 0, we
+ * must start the lookup from the current address, because
+ * handle_mm_fault() may back out if there's any difficulty.
+ *
+ * VM_FAULT_SIGBUS and VM_FAULT_SIGSEGV are unexpected but
+ * maybe they could trigger in the future on concurrent
+ * truncation. In that case, the shared zeropage would be gone
+ * and we can simply retry and make progress.
+ */
+ cond_resched();
+ goto retry;
+ }
+
+ return 0;
+ }
+
+ static int __s390_disable_cow_sharing(struct mm_struct *mm)
+ {
+ int rc;
+
+ if (!mm->context.allow_cow_sharing)
+ return 0;
+
+ mm->context.allow_cow_sharing = 0;
+
+ /* Replace all shared zeropages by anonymous pages. */
+ rc = __s390_unshare_zeropages(mm);
/*
* Make sure to disable KSM (if enabled for the whole process or
* individual VMAs). Note that nothing currently hinders user space
* from re-enabling it.
*/
- return ksm_disable(current->mm);
+ if (!rc)
+ rc = ksm_disable(mm);
+ if (rc)
+ mm->context.allow_cow_sharing = 1;
+ return rc;
+ }
+
+ /*
+ * Disable most COW-sharing of memory pages for the whole process:
+ * (1) Disable KSM and unmerge/unshare any KSM pages.
+ * (2) Disallow shared zeropages and unshare any zerpages that are mapped.
+ *
+ * Not that we currently don't bother with COW-shared pages that are shared
+ * with parent/child processes due to fork().
+ */
+ int s390_disable_cow_sharing(void)
+ {
+ int rc;
+
+ mmap_write_lock(current->mm);
+ rc = __s390_disable_cow_sharing(current->mm);
+ mmap_write_unlock(current->mm);
+ return rc;
}
- EXPORT_SYMBOL_GPL(gmap_mark_unmergeable);
+ EXPORT_SYMBOL_GPL(s390_disable_cow_sharing);
/*
* Enable storage key handling from now on and initialize the storage
return 0;
start = pmd_val(*pmd) & HPAGE_MASK;
- end = start + HPAGE_SIZE - 1;
+ end = start + HPAGE_SIZE;
__storage_key_init_range(start, end);
set_bit(PG_arch_1, &page->flags);
cond_resched();
goto out_up;
mm->context.uses_skeys = 1;
- rc = gmap_mark_unmergeable();
+ rc = __s390_disable_cow_sharing(mm);
if (rc) {
mm->context.uses_skeys = 0;
goto out_up;
projects / linux.git / commitdiff