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From:   Leonardo Bras <leonardo@linux.ibm.com>
To:     linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Cc:     Leonardo Bras <leonardo@linux.ibm.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
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        "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
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        Andrew Morton <akpm@linux-foundation.org>,
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        Nicholas Piggin <npiggin@gmail.com>,
        Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>,
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        Allison Randal <allison@lohutok.net>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Mike Rapoport <rppt@linux.ibm.com>,
        YueHaibing <yuehaibing@huawei.com>,
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        Jason Gunthorpe <jgg@ziepe.ca>,
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        Keith Busch <keith.busch@intel.com>
Subject: [PATCH v2 04/11] powerpc/mce_power: Applies counting method to monitor lockless pgtbl walks
Date:   Fri, 20 Sep 2019 16:50:40 -0300
Message-Id: <20190920195047.7703-5-leonardo@linux.ibm.com>
In-Reply-To: <20190920195047.7703-1-leonardo@linux.ibm.com>
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Applies the counting-based method for monitoring lockless pgtable walks on
addr_to_pfn().

Signed-off-by: Leonardo Bras <leonardo@linux.ibm.com>
---
 arch/powerpc/kernel/mce_power.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/mce_power.c b/arch/powerpc/kernel/mce_power.c
index a814d2dfb5b0..0f2f87da4cd1 100644
--- a/arch/powerpc/kernel/mce_power.c
+++ b/arch/powerpc/kernel/mce_power.c
@@ -27,6 +27,7 @@ unsigned long addr_to_pfn(struct pt_regs *regs, unsigned long addr)
 {
 	pte_t *ptep;
 	unsigned long flags;
+	unsigned long pfn;
 	struct mm_struct *mm;
 
 	if (user_mode(regs))
@@ -34,15 +35,21 @@ unsigned long addr_to_pfn(struct pt_regs *regs, unsigned long addr)
 	else
 		mm = &init_mm;
 
+	start_lockless_pgtbl_walk(mm);
 	local_irq_save(flags);
 	if (mm == current->mm)
 		ptep = find_current_mm_pte(mm->pgd, addr, NULL, NULL);
 	else
 		ptep = find_init_mm_pte(addr, NULL);
-	local_irq_restore(flags);
+
 	if (!ptep || pte_special(*ptep))
-		return ULONG_MAX;
-	return pte_pfn(*ptep);
+		pfn = ULONG_MAX;
+	else
+		pfn = pte_pfn(*ptep);
+
+	local_irq_restore(flags);
+	end_lockless_pgtbl_walk(mm);
+	return pfn;
 }
 
 /* flush SLBs and reload */
-- 
2.20.1