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Message-Id: <20210430195232.30491-19-michel@lespinasse.org>
Date: Fri, 30 Apr 2021 12:52:19 -0700
From: Michel Lespinasse <michel@...pinasse.org>
To: Linux-MM <linux-mm@...ck.org>,
Linux-Kernel <linux-kernel@...r.kernel.org>
Cc: Laurent Dufour <ldufour@...ux.ibm.com>,
Peter Zijlstra <peterz@...radead.org>,
Michal Hocko <mhocko@...e.com>,
Matthew Wilcox <willy@...radead.org>,
Rik van Riel <riel@...riel.com>,
Paul McKenney <paulmck@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Suren Baghdasaryan <surenb@...gle.com>,
Joel Fernandes <joelaf@...gle.com>,
Andy Lutomirski <luto@...nel.org>,
Michel Lespinasse <michel@...pinasse.org>
Subject: [PATCH 18/29] mm: enable speculative fault handling through do_anonymous_page()
in x86 fault handler, only attempt spf if the vma is anonymous.
In do_handle_mm_fault(), let speculative page faults proceed as long
as they fall into anonymous vmas. This enables the speculative
handling code in __handle_mm_fault() and do_anonymous_page().
In handle_pte_fault(), if vmf->pte is set (the original pte was not
pte_none), catch speculative faults and return VM_FAULT_RETRY as
those cases are not implemented yet. Also assert that do_fault()
is not reached in the speculative case.
Signed-off-by: Michel Lespinasse <michel@...pinasse.org>
---
arch/x86/mm/fault.c | 2 +-
mm/memory.c | 16 ++++++++++++----
2 files changed, 13 insertions(+), 5 deletions(-)
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 0e8abe43d032..463061186827 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1327,7 +1327,7 @@ void do_user_addr_fault(struct pt_regs *regs,
goto spf_abort;
rcu_read_lock();
vma = find_vma(mm, address);
- if (!vma || vma->vm_start > address) {
+ if (!vma || vma->vm_start > address || !vma_is_anonymous(vma)) {
rcu_read_unlock();
goto spf_abort;
}
diff --git a/mm/memory.c b/mm/memory.c
index d95826c48f1d..eceb1b6e904c 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4120,6 +4120,8 @@ static vm_fault_t do_fault(struct vm_fault *vmf)
struct mm_struct *vm_mm = vma->vm_mm;
vm_fault_t ret;
+ VM_BUG_ON(vmf->flags & FAULT_FLAG_SPECULATIVE);
+
/*
* The VMA was not fully populated on mmap() or missing VM_DONTEXPAND
*/
@@ -4357,6 +4359,11 @@ 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);
@@ -4685,8 +4692,7 @@ vm_fault_t do_handle_mm_fault(struct vm_area_struct *vma,
{
vm_fault_t ret;
- if (flags & FAULT_FLAG_SPECULATIVE)
- return VM_FAULT_RETRY;
+ VM_BUG_ON((flags & FAULT_FLAG_SPECULATIVE) && !vma_is_anonymous(vma));
__set_current_state(TASK_RUNNING);
@@ -4708,10 +4714,12 @@ vm_fault_t do_handle_mm_fault(struct vm_area_struct *vma,
if (flags & FAULT_FLAG_USER)
mem_cgroup_enter_user_fault();
- if (unlikely(is_vm_hugetlb_page(vma)))
+ if (unlikely(is_vm_hugetlb_page(vma))) {
+ VM_BUG_ON(flags & FAULT_FLAG_SPECULATIVE);
ret = hugetlb_fault(vma->vm_mm, vma, address, flags);
- else
+ } else {
ret = __handle_mm_fault(vma, address, flags, seq);
+ }
if (flags & FAULT_FLAG_USER) {
mem_cgroup_exit_user_fault();
--
2.20.1
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