linux-kernel - [PATCH v2 21/35] mm: enable speculative fault handling in do_numa

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Message-Id: <20220128131006.67712-22-michel@lespinasse.org>
Date:   Fri, 28 Jan 2022 05:09:52 -0800
From:   Michel Lespinasse <michel@...pinasse.org>
To:     Linux-MM <linux-mm@...ck.org>, linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     kernel-team@...com, Laurent Dufour <ldufour@...ux.ibm.com>,
        Jerome Glisse <jglisse@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Michal Hocko <mhocko@...e.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Davidlohr Bueso <dave@...olabs.net>,
        Matthew Wilcox <willy@...radead.org>,
        Liam Howlett <liam.howlett@...cle.com>,
        Rik van Riel <riel@...riel.com>,
        Paul McKenney <paulmck@...nel.org>,
        Song Liu <songliubraving@...com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Minchan Kim <minchan@...gle.com>,
        Joel Fernandes <joelaf@...gle.com>,
        David Rientjes <rientjes@...gle.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Michel Lespinasse <michel@...pinasse.org>
Subject: [PATCH v2 21/35] mm: enable speculative fault handling in do_numa_page()

Change handle_pte_fault() to allow speculative fault execution to proceed
through do_numa_page().

do_swap_page() does not implement speculative execution yet, so it
needs to abort with VM_FAULT_RETRY in that case.

Signed-off-by: Michel Lespinasse <michel@...pinasse.org>
---
 mm/memory.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 083e015ff194..73b1a328b797 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3589,6 +3589,11 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 	vm_fault_t ret = 0;
 	void *shadow = NULL;
 
+	if (vmf->flags & FAULT_FLAG_SPECULATIVE) {
+		pte_unmap(vmf->pte);
+		return VM_FAULT_RETRY;
+	}
+
 	if (!pte_unmap_same(vmf))
 		goto out;
 
@@ -4611,17 +4616,17 @@ static vm_fault_t handle_pte_fault(struct vm_fault *vmf)
 			return do_fault(vmf);
 	}
 
-	if (vmf->flags & FAULT_FLAG_SPECULATIVE) {
-		pte_unmap(vmf->pte);
-		return VM_FAULT_RETRY;
-	}
-
 	if (!pte_present(vmf->orig_pte))
 		return do_swap_page(vmf);
 
 	if (pte_protnone(vmf->orig_pte) && vma_is_accessible(vmf->vma))
 		return do_numa_page(vmf);
 
+	if (vmf->flags & FAULT_FLAG_SPECULATIVE) {
+		pte_unmap(vmf->pte);
+		return VM_FAULT_RETRY;
+	}
+
 	vmf->ptl = pte_lockptr(vmf->vma->vm_mm, vmf->pmd);
 	spin_lock(vmf->ptl);
 	entry = vmf->orig_pte;
-- 
2.20.1