linux-kernel - [PATCH v2 04/11] powerpc/mce_power: Applies counting method to monitor lockless pgtbl walks

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Message-Id: <20190920195047.7703-5-leonardo@linux.ibm.com>
Date:   Fri, 20 Sep 2019 16:50:40 -0300
From:   Leonardo Bras <leonardo@...ux.ibm.com>
To:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Cc:     Leonardo Bras <leonardo@...ux.ibm.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Arnd Bergmann <arnd@...db.de>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        Christophe Leroy <christophe.leroy@....fr>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Nicholas Piggin <npiggin@...il.com>,
        Mahesh Salgaonkar <mahesh@...ux.vnet.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Richard Fontana <rfontana@...hat.com>,
        Ganesh Goudar <ganeshgr@...ux.ibm.com>,
        Allison Randal <allison@...utok.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        YueHaibing <yuehaibing@...wei.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        John Hubbard <jhubbard@...dia.com>,
        Keith Busch <keith.busch@...el.com>
Subject: [PATCH v2 04/11] powerpc/mce_power: Applies counting method to monitor lockless pgtbl walks

Applies the counting-based method for monitoring lockless pgtable walks on
addr_to_pfn().

Signed-off-by: Leonardo Bras <leonardo@...ux.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