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SubjectRe: linux-next: manual merge of the akpm-current tree with the tip tree
Hi all,

On Mon, 25 May 2020 21:04:43 +1000 Stephen Rothwell <sfr@canb.auug.org.au> wrote:
>
> 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.
>
> 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,

This is now a conflict between commit

94709049fb84 ("Merge branch 'akpm' (patches from Andrew)")

from Linus' tree and the above tip tree commit.

--
Cheers,
Stephen Rothwell
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