Subject: linux-next: manual merge of the akpm-current tree with the tip tree

From: Stephen Rothwell <[email-masked]>
Date: Mon, 25 May 2020 21:04:43 +1000

Hi all,

Today's linux-next merge of the akpm-current tree got a conflict in:

  arch/x86/mm/tlb.c

between commit:

  83ce56f712af ("x86/mm: Refactor cond_ibpb() to support other use cases")

from the tip tree and commit:

  36c8e34d03a1 ("x86/mm: remove vmalloc faulting")

from the akpm-current tree.

I fixed it up (see below) and can carry the fix as necessary. This
is now fixed as far as linux-next is concerned, but any non trivial
conflicts should be mentioned to your upstream maintainer when your tree
is submitted for merging.  You may also want to consider cooperating
with the maintainer of the conflicting tree to minimise any particularly
complex conflicts.

-- 
Cheers,
Stephen Rothwell

diff --cc arch/x86/mm/tlb.c
index c8524c506ab0,f3fe261e5936..000000000000
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@@ -345,48 -161,16 +345,20 @@@ void switch_mm(struct mm_struct *prev, 
  	local_irq_restore(flags);
  }
  
- static void sync_current_stack_to_mm(struct mm_struct *mm)
- {
- 	unsigned long sp = current_stack_pointer;
- 	pgd_t *pgd = pgd_offset(mm, sp);
- 
- 	if (pgtable_l5_enabled()) {
- 		if (unlikely(pgd_none(*pgd))) {
- 			pgd_t *pgd_ref = pgd_offset_k(sp);
- 
- 			set_pgd(pgd, *pgd_ref);
- 		}
- 	} else {
- 		/*
- 		 * "pgd" is faked.  The top level entries are "p4d"s, so sync
- 		 * the p4d.  This compiles to approximately the same code as
- 		 * the 5-level case.
- 		 */
- 		p4d_t *p4d = p4d_offset(pgd, sp);
- 
- 		if (unlikely(p4d_none(*p4d))) {
- 			pgd_t *pgd_ref = pgd_offset_k(sp);
- 			p4d_t *p4d_ref = p4d_offset(pgd_ref, sp);
- 
- 			set_p4d(p4d, *p4d_ref);
- 		}
- 	}
- }
- 
 -static inline unsigned long mm_mangle_tif_spec_ib(struct task_struct *next)
 +static inline unsigned long mm_mangle_tif_spec_bits(struct task_struct *next)
  {
  	unsigned long next_tif = task_thread_info(next)->flags;
 -	unsigned long ibpb = (next_tif >> TIF_SPEC_IB) & LAST_USER_MM_IBPB;
 +	unsigned long spec_bits = (next_tif >> TIF_SPEC_IB) & LAST_USER_MM_SPEC_MASK;
  
 -	return (unsigned long)next->mm | ibpb;
 +	BUILD_BUG_ON(TIF_SPEC_L1D_FLUSH != TIF_SPEC_IB + 1);
 +
 +	return (unsigned long)next->mm | spec_bits;
  }
  
 -static void cond_ibpb(struct task_struct *next)
 +static void cond_mitigation(struct task_struct *next)
  {
 +	unsigned long prev_mm, next_mm;
 +
  	if (!next || !next->mm)
  		return;
  
@@@ -587,20 -343,12 +559,11 @@@ void switch_mm_irqs_off(struct mm_struc
  		need_flush = true;
  	} else {
  		/*
 -		 * Avoid user/user BTB poisoning by flushing the branch
 -		 * predictor when switching between processes. This stops
 -		 * one process from doing Spectre-v2 attacks on another.
 +		 * Apply process to process speculation vulnerability
 +		 * mitigations if applicable.
  		 */
 -		cond_ibpb(tsk);
 +		cond_mitigation(tsk);
  
- 		if (IS_ENABLED(CONFIG_VMAP_STACK)) {
- 			/*
- 			 * If our current stack is in vmalloc space and isn't
- 			 * mapped in the new pgd, we'll double-fault.  Forcibly
- 			 * map it.
- 			 */
- 			sync_current_stack_to_mm(next);
- 		}
- 
  		/*
  		 * Stop remote flushes for the previous mm.
  		 * Skip kernel threads; we never send init_mm TLB flushing IPIs,