linux-kernel - [PATCH v4 06/11] powerpc/mm/book3s64/hash: Applies counting method to monitor lockless pgtbl walks

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Message-Id: <20190927234008.11513-7-leonardo@linux.ibm.com>
Date:   Fri, 27 Sep 2019 20:40:03 -0300
From:   Leonardo Bras <leonardo@...ux.ibm.com>
To:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        kvm-ppc@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-mm@...ck.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>,
        Allison Randal <allison@...utok.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ganesh Goudar <ganeshgr@...ux.ibm.com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        YueHaibing <yuehaibing@...wei.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ira Weiny <ira.weiny@...el.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        John Hubbard <jhubbard@...dia.com>,
        Keith Busch <keith.busch@...el.com>
Subject: [PATCH v4 06/11] powerpc/mm/book3s64/hash: Applies counting method to monitor lockless pgtbl walks

Applies the counting-based method for monitoring all hash-related functions
that do lockless pagetable walks.

hash_page_mm: Adds comment that explain that there is no need to
local_int_disable/save given that it is only called from DataAccess
interrupt, so interrupts are already disabled.

Signed-off-by: Leonardo Bras <leonardo@...ux.ibm.com>
---
 arch/powerpc/mm/book3s64/hash_tlb.c   |  2 ++
 arch/powerpc/mm/book3s64/hash_utils.c | 12 +++++++++++-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/mm/book3s64/hash_tlb.c b/arch/powerpc/mm/book3s64/hash_tlb.c
index 4a70d8dd39cd..5e5213c3f7c4 100644
--- a/arch/powerpc/mm/book3s64/hash_tlb.c
+++ b/arch/powerpc/mm/book3s64/hash_tlb.c
@@ -209,6 +209,7 @@ void __flush_hash_table_range(struct mm_struct *mm, unsigned long start,
 	 * to being hashed). This is not the most performance oriented
 	 * way to do things but is fine for our needs here.
 	 */
+	start_lockless_pgtbl_walk(mm);
 	local_irq_save(flags);
 	arch_enter_lazy_mmu_mode();
 	for (; start < end; start += PAGE_SIZE) {
@@ -230,6 +231,7 @@ void __flush_hash_table_range(struct mm_struct *mm, unsigned long start,
 	}
 	arch_leave_lazy_mmu_mode();
 	local_irq_restore(flags);
+	end_lockless_pgtbl_walk(mm);
 }
 
 void flush_tlb_pmd_range(struct mm_struct *mm, pmd_t *pmd, unsigned long addr)
diff --git a/arch/powerpc/mm/book3s64/hash_utils.c b/arch/powerpc/mm/book3s64/hash_utils.c
index b8ad14bb1170..8615fab87c43 100644
--- a/arch/powerpc/mm/book3s64/hash_utils.c
+++ b/arch/powerpc/mm/book3s64/hash_utils.c
@@ -1321,7 +1321,11 @@ int hash_page_mm(struct mm_struct *mm, unsigned long ea,
 		ea &= ~((1ul << mmu_psize_defs[psize].shift) - 1);
 #endif /* CONFIG_PPC_64K_PAGES */
 
-	/* Get PTE and page size from page tables */
+	/* Get PTE and page size from page tables :
+	 * Called in from DataAccess interrupt (data_access_common: 0x300),
+	 * interrupts are disabled here.
+	 */
+	start_lockless_pgtbl_walk(mm);
 	ptep = find_linux_pte(pgdir, ea, &is_thp, &hugeshift);
 	if (ptep == NULL || !pte_present(*ptep)) {
 		DBG_LOW(" no PTE !\n");
@@ -1438,6 +1442,7 @@ int hash_page_mm(struct mm_struct *mm, unsigned long ea,
 	DBG_LOW(" -> rc=%d\n", rc);
 
 bail:
+	end_lockless_pgtbl_walk(mm);
 	exception_exit(prev_state);
 	return rc;
 }
@@ -1547,10 +1552,12 @@ void hash_preload(struct mm_struct *mm, unsigned long ea,
 	vsid = get_user_vsid(&mm->context, ea, ssize);
 	if (!vsid)
 		return;
+
 	/*
 	 * Hash doesn't like irqs. Walking linux page table with irq disabled
 	 * saves us from holding multiple locks.
 	 */
+	start_lockless_pgtbl_walk(mm);
 	local_irq_save(flags);
 
 	/*
@@ -1597,6 +1604,7 @@ void hash_preload(struct mm_struct *mm, unsigned long ea,
 				   pte_val(*ptep));
 out_exit:
 	local_irq_restore(flags);
+	end_lockless_pgtbl_walk(mm);
 }
 
 #ifdef CONFIG_PPC_MEM_KEYS
@@ -1613,11 +1621,13 @@ u16 get_mm_addr_key(struct mm_struct *mm, unsigned long address)
 	if (!mm || !mm->pgd)
 		return 0;
 
+	start_lockless_pgtbl_walk(mm);
 	local_irq_save(flags);
 	ptep = find_linux_pte(mm->pgd, address, NULL, NULL);
 	if (ptep)
 		pkey = pte_to_pkey_bits(pte_val(READ_ONCE(*ptep)));
 	local_irq_restore(flags);
+	end_lockless_pgtbl_walk(mm);
 
 	return pkey;
 }
-- 
2.20.1