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From: Jisheng Zhang <jszhang@kernel.org>
To: Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org,
	Suren Baghdasaryan <surenb@google.com>
Subject: [PATCH] arm64: mm: pass original fault address to handle_mm_fault() in PER_VMA_LOCK block
Date: Wed, 24 May 2023 21:13:05 +0800	[thread overview]
Message-ID: <20230524131305.2808-1-jszhang@kernel.org> (raw)

When reading the arm64's PER_VMA_LOCK support code, I found a bit
difference between arm64 and other arch when calling handle_mm_fault()
during VMA lock-based page fault handling: the fault address is masked
before passing to handle_mm_fault(). This is also different from the
usage in mmap_lock-based handling. I think we need to pass the
original fault address to handle_mm_fault() as we did in
commit 84c5e23edecd ("arm64: mm: Pass original fault address to
handle_mm_fault()").

If we go through the code path further, we can find that the "masked"
fault address can cause mismatched fault address between perf sw
major/minor page fault sw event and perf page fault sw event:

do_page_fault
  perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, ..., addr)   // orig addr
  handle_mm_fault
    mm_account_fault
      perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, ...) // masked addr

Fixes: cd7f176aea5f ("arm64/mm: try VMA lock-based page fault handling first")
Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
---
 arch/arm64/mm/fault.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index cb21ccd7940d..6045a5117ac1 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -600,8 +600,7 @@ static int __kprobes do_page_fault(unsigned long far, unsigned long esr,
 		vma_end_read(vma);
 		goto lock_mmap;
 	}
-	fault = handle_mm_fault(vma, addr & PAGE_MASK,
-				mm_flags | FAULT_FLAG_VMA_LOCK, regs);
+	fault = handle_mm_fault(vma, addr, mm_flags | FAULT_FLAG_VMA_LOCK, regs);
 	vma_end_read(vma);
 
 	if (!(fault & VM_FAULT_RETRY)) {
-- 
2.40.1


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WARNING: multiple messages have this Message-ID (diff)
From: Jisheng Zhang <jszhang@kernel.org>
To: Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org,
	Suren Baghdasaryan <surenb@google.com>
Subject: [PATCH] arm64: mm: pass original fault address to handle_mm_fault() in PER_VMA_LOCK block
Date: Wed, 24 May 2023 21:13:05 +0800	[thread overview]
Message-ID: <20230524131305.2808-1-jszhang@kernel.org> (raw)

When reading the arm64's PER_VMA_LOCK support code, I found a bit
difference between arm64 and other arch when calling handle_mm_fault()
during VMA lock-based page fault handling: the fault address is masked
before passing to handle_mm_fault(). This is also different from the
usage in mmap_lock-based handling. I think we need to pass the
original fault address to handle_mm_fault() as we did in
commit 84c5e23edecd ("arm64: mm: Pass original fault address to
handle_mm_fault()").

If we go through the code path further, we can find that the "masked"
fault address can cause mismatched fault address between perf sw
major/minor page fault sw event and perf page fault sw event:

do_page_fault
  perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, ..., addr)   // orig addr
  handle_mm_fault
    mm_account_fault
      perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, ...) // masked addr

Fixes: cd7f176aea5f ("arm64/mm: try VMA lock-based page fault handling first")
Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
---
 arch/arm64/mm/fault.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index cb21ccd7940d..6045a5117ac1 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -600,8 +600,7 @@ static int __kprobes do_page_fault(unsigned long far, unsigned long esr,
 		vma_end_read(vma);
 		goto lock_mmap;
 	}
-	fault = handle_mm_fault(vma, addr & PAGE_MASK,
-				mm_flags | FAULT_FLAG_VMA_LOCK, regs);
+	fault = handle_mm_fault(vma, addr, mm_flags | FAULT_FLAG_VMA_LOCK, regs);
 	vma_end_read(vma);
 
 	if (!(fault & VM_FAULT_RETRY)) {
-- 
2.40.1


             reply	other threads:[~2023-05-24 13:24 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-05-24 13:13 Jisheng Zhang [this message]
2023-05-24 13:13 ` [PATCH] arm64: mm: pass original fault address to handle_mm_fault() in PER_VMA_LOCK block Jisheng Zhang
2023-05-25 17:03 ` Catalin Marinas
2023-05-25 17:03   ` Catalin Marinas
2023-06-02 12:33 ` Will Deacon
2023-06-02 12:33   ` Will Deacon
  -- strict thread matches above, loose matches on Subject: below --
2023-05-24 13:12 Jisheng Zhang
2023-05-24 13:12 ` Jisheng Zhang
2023-05-24 13:26 ` Jisheng Zhang
2023-05-24 13:26   ` Jisheng Zhang
2023-05-24 14:39   ` Suren Baghdasaryan
2023-05-24 14:39     ` Suren Baghdasaryan
2023-05-25  7:00 ` Anshuman Khandual
2023-05-25  7:00   ` Anshuman Khandual

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