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Subject[PATCH 2/8] x86/mm/cpa: Move flush_tlb_all()
There is an atom errata, where we do a local TLB invalidate right
before we return and then do a global TLB invalidate.

Move the global invalidate up a little bit and avoid the local
invalidate entirely.

This does put the global invalidate under pgd_lock, but that shouldn't
matter.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/x86/mm/pageattr.c | 44 +++++++++++++++++---------------------------
1 file changed, 17 insertions(+), 27 deletions(-)

--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -996,14 +996,24 @@ __split_large_page(struct cpa_data *cpa,
__set_pmd_pte(kpte, address, mk_pte(base, __pgprot(_KERNPG_TABLE)));

/*
- * Intel Atom errata AAH41 workaround.
+ * Do a global flush tlb after splitting the large page
+ * and before we do the actual change page attribute in the PTE.
*
- * The real fix should be in hw or in a microcode update, but
- * we also probabilistically try to reduce the window of having
- * a large TLB mixed with 4K TLBs while instruction fetches are
- * going on.
+ * Without this, we violate the TLB application note, that says:
+ * "The TLBs may contain both ordinary and large-page
+ * translations for a 4-KByte range of linear addresses. This
+ * may occur if software modifies the paging structures so that
+ * the page size used for the address range changes. If the two
+ * translations differ with respect to page frame or attributes
+ * (e.g., permissions), processor behavior is undefined and may
+ * be implementation-specific."
+ *
+ * We do this global tlb flush inside the cpa_lock, so that we
+ * don't allow any other cpu, with stale tlb entries change the
+ * page attribute in parallel, that also falls into the
+ * just split large page entry.
*/
- __flush_tlb_all();
+ flush_tlb_all();
spin_unlock(&pgd_lock);

return 0;
@@ -1528,28 +1538,8 @@ static int __change_page_attr(struct cpa
* We have to split the large page:
*/
err = split_large_page(cpa, kpte, address);
- if (!err) {
- /*
- * Do a global flush tlb after splitting the large page
- * and before we do the actual change page attribute in the PTE.
- *
- * With out this, we violate the TLB application note, that says
- * "The TLBs may contain both ordinary and large-page
- * translations for a 4-KByte range of linear addresses. This
- * may occur if software modifies the paging structures so that
- * the page size used for the address range changes. If the two
- * translations differ with respect to page frame or attributes
- * (e.g., permissions), processor behavior is undefined and may
- * be implementation-specific."
- *
- * We do this global tlb flush inside the cpa_lock, so that we
- * don't allow any other cpu, with stale tlb entries change the
- * page attribute in parallel, that also falls into the
- * just split large page entry.
- */
- flush_tlb_all();
+ if (!err)
goto repeat;
- }

return err;
}

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