linux-kernel - [PATCH 4.9 016/119] sparc64: reset mm cpumask after wrap

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Date:   Mon, 12 Jun 2017 17:24:38 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Pavel Tatashin <pasha.tatashin@...cle.com>,
        Bob Picco <bob.picco@...cle.com>,
        Steven Sistare <steven.sistare@...cle.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.9 016/119] sparc64: reset mm cpumask after wrap

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Pavel Tatashin <pasha.tatashin@...cle.com>

[ Upstream commit 588974857359861891f478a070b1dc7ae04a3880 ]

After a wrap (getting a new context version) a process must get a new
context id, which means that we would need to flush the context id from
the TLB before running for the first time with this ID on every CPU. But,
we use mm_cpumask to determine if this process has been running on this CPU
before, and this mask is not reset after a wrap. So, there are two possible
fixes for this issue:

1. Clear mm cpumask whenever mm gets a new context id
2. Unconditionally flush context every time process is running on a CPU

This patch implements the first solution

Signed-off-by: Pavel Tatashin <pasha.tatashin@...cle.com>
Reviewed-by: Bob Picco <bob.picco@...cle.com>
Reviewed-by: Steven Sistare <steven.sistare@...cle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/sparc/mm/init_64.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/arch/sparc/mm/init_64.c
+++ b/arch/sparc/mm/init_64.c
@@ -710,6 +710,8 @@ void get_new_mmu_context(struct mm_struc
 			goto out;
 		}
 	}
+	if (mm->context.sparc64_ctx_val)
+		cpumask_clear(mm_cpumask(mm));
 	mmu_context_bmap[new_ctx>>6] |= (1UL << (new_ctx & 63));
 	new_ctx |= (tlb_context_cache & CTX_VERSION_MASK);
 out: