[RFC v2 19/26] mm/asi: Add option to map RCU data

From: Alexandre Chartre <alexandre.chartre@oracle.com>
To: pbonzini@redhat.com, rkrcmar@redhat.com, tglx@linutronix.de,
	mingo@redhat.com, bp@alien8.de, hpa@zytor.com,
	dave.hansen@linux.intel.com, luto@kernel.org,
	peterz@infradead.org, kvm@vger.kernel.org, x86@kernel.org,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Cc: konrad.wilk@oracle.com, jan.setjeeilers@oracle.com,
	liran.alon@oracle.com, jwadams@google.com, graf@amazon.de,
	rppt@linux.vnet.ibm.com, alexandre.chartre@oracle.com
Subject: [RFC v2 19/26] mm/asi: Add option to map RCU data
Date: Thu, 11 Jul 2019 16:25:31 +0200	[thread overview]
Message-ID: <1562855138-19507-20-git-send-email-alexandre.chartre@oracle.com> (raw)
In-Reply-To: <1562855138-19507-1-git-send-email-alexandre.chartre@oracle.com>

Add an option to map RCU data when creating an ASI. This will map
the percpu rcu_data (which is not exported by the kernel), and
allow ASI to use RCU without faulting.

Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
---
 arch/x86/include/asm/asi.h |    1 +
 arch/x86/mm/asi.c          |    4 ++++
 2 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/asi.h b/arch/x86/include/asm/asi.h
index a277e43..8199618 100644
--- a/arch/x86/include/asm/asi.h
+++ b/arch/x86/include/asm/asi.h
@@ -18,6 +18,7 @@
 #define ASI_MAP_STACK_CANARY	0x01	/* map stack canary */
 #define ASI_MAP_CPU_PTR		0x02	/* for get_cpu_var()/this_cpu_ptr() */
 #define ASI_MAP_CURRENT_TASK	0x04	/* map the current task */
+#define ASI_MAP_RCU_DATA	0x08	/* map rcu data */
 
 enum page_table_level {
 	PGT_LEVEL_PTE,
diff --git a/arch/x86/mm/asi.c b/arch/x86/mm/asi.c
index acd1135..20c23dc 100644
--- a/arch/x86/mm/asi.c
+++ b/arch/x86/mm/asi.c
@@ -7,6 +7,7 @@
 
 #include <linux/export.h>
 #include <linux/gfp.h>
+#include <linux/irq_work.h>
 #include <linux/mm.h>
 #include <linux/printk.h>
 #include <linux/sched/debug.h>
@@ -16,6 +17,8 @@
 #include <asm/bug.h>
 #include <asm/mmu_context.h>
 
+#include "../../../kernel/rcu/tree.h"
+
 /* ASI sessions, one per cpu */
 DEFINE_PER_CPU_PAGE_ALIGNED(struct asi_session, cpu_asi_session);
 
@@ -29,6 +32,7 @@ struct asi_map_option asi_map_percpu_options[] = {
 	{ ASI_MAP_STACK_CANARY, &fixed_percpu_data, sizeof(fixed_percpu_data) },
 	{ ASI_MAP_CPU_PTR, &this_cpu_off, sizeof(this_cpu_off) },
 	{ ASI_MAP_CURRENT_TASK, &current_task, sizeof(current_task) },
+	{ ASI_MAP_RCU_DATA, &rcu_data, sizeof(rcu_data) },
 };
 
 static void asi_log_fault(struct asi *asi, struct pt_regs *regs,
-- 
1.7.1

