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

From: Leonardo Bras <leonardo@linux.ibm.com>
To: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
	kvm-ppc@vger.kernel.org, linux-arch@vger.kernel.org,
	linux-mm@kvack.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>,
	Arnd Bergmann <arnd@arndb.de>,
	"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
	Christophe Leroy <christophe.leroy@c-s.fr>,
	Andrew Morton <akpm@linux-foundation.org>,
	Dan Williams <dan.j.williams@intel.com>,
	Nicholas Piggin <npiggin@gmail.com>,
	Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>,
	Allison Randal <allison@lohutok.net>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ganesh Goudar <ganeshgr@linux.ibm.com>,
	Mike Rapoport <rppt@linux.ibm.com>,
	YueHaibing <yuehaibing@huawei.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Ira Weiny <ira.weiny@intel.com>, Jason Gunthorpe <jgg@ziepe.ca>,
	John Hubbard <jhubbard@nvidia.com>,
	Keith Busch <keith.busch@intel.com>
Subject: [PATCH v4 06/11] powerpc/mm/book3s64/hash: Applies counting method to monitor lockless pgtbl walks
Date: Fri, 27 Sep 2019 20:40:03 -0300	[thread overview]
Message-ID: <20190927234008.11513-7-leonardo@linux.ibm.com> (raw)
In-Reply-To: <20190927234008.11513-1-leonardo@linux.ibm.com>

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@linux.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


