[PATCH v2 11/12] ARM: wire up UEFI init and runtime support

On Mon, Nov 16, 2015 at 07:32:36PM +0100, Ard Biesheuvel wrote:

+static inline void efi_set_pgd(struct mm_struct *mm)
+{
+	if (unlikely(mm->context.vmalloc_seq != init_mm.context.vmalloc_seq))
+		__check_vmalloc_seq(mm);
+
+	cpu_switch_mm(mm->pgd, mm);
+
+	flush_tlb_all();
+	if (icache_is_vivt_asid_tagged())
+		__flush_icache_all();
+}

I don't think that's sufficient.  There's a gap between switching the mm
and flushing the TLBs where we could have different global TLB entries
from those in the page tables - and that can cause problems with CPUs
which speculatively prefetch.  Some CPUs raise exceptions for this...

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