linux-kernel - [RFC][Patch v8 2/7] KVM: Enabling guest free page hinting via static key

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Date:   Mon,  4 Feb 2019 15:18:49 -0500
From:   Nitesh Narayan Lal <nitesh@...hat.com>
To:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        pbonzini@...hat.com, lcapitulino@...hat.com, pagupta@...hat.com,
        wei.w.wang@...el.com, yang.zhang.wz@...il.com, riel@...riel.com,
        david@...hat.com, mst@...hat.com, dodgen@...gle.com,
        konrad.wilk@...cle.com, dhildenb@...hat.com, aarcange@...hat.com
Subject: [RFC][Patch v8 2/7] KVM: Enabling guest free page hinting via static key

This patch enables the guest free page hinting support
to enable or disable based on the STATIC key which
could be set via sysctl.

Signed-off-by: Nitesh Narayan Lal <nitesh@...hat.com>
---
 include/linux/gfp.h          |  2 ++
 include/linux/page_hinting.h |  5 +++++
 kernel/sysctl.c              |  9 +++++++++
 virt/kvm/page_hinting.c      | 23 +++++++++++++++++++++++
 4 files changed, 39 insertions(+)

diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index e596527284ba..8389219a076a 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -461,6 +461,8 @@ static inline struct zonelist *node_zonelist(int nid, gfp_t flags)
 #define HAVE_ARCH_FREE_PAGE
 static inline void arch_free_page(struct page *page, int order)
 {
+	if (!static_branch_unlikely(&guest_page_hinting_key))
+		return;
 	guest_free_page(page, order);
 }
 #endif
diff --git a/include/linux/page_hinting.h b/include/linux/page_hinting.h
index b54f7428f348..9bdcf63e1306 100644
--- a/include/linux/page_hinting.h
+++ b/include/linux/page_hinting.h
@@ -14,4 +14,9 @@ struct hypervisor_pages {
 	unsigned int order;
 };
 
+extern int guest_page_hinting_flag;
+extern struct static_key_false guest_page_hinting_key;
+
+int guest_page_hinting_sysctl(struct ctl_table *table, int write,
+			      void __user *buffer, size_t *lenp, loff_t *ppos);
 void guest_free_page(struct page *page, int order);
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index ba4d9e85feb8..5d53629c9bfb 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1690,6 +1690,15 @@ static struct ctl_table vm_table[] = {
 		.extra1		= (void *)&mmap_rnd_compat_bits_min,
 		.extra2		= (void *)&mmap_rnd_compat_bits_max,
 	},
+#endif
+#ifdef CONFIG_KVM_FREE_PAGE_HINTING
+	{
+		.procname	= "guest-page-hinting",
+		.data		= &guest_page_hinting_flag,
+		.maxlen		= sizeof(guest_page_hinting_flag),
+		.mode		= 0644,
+		.proc_handler   = guest_page_hinting_sysctl,
+	},
 #endif
 	{ }
 };
diff --git a/virt/kvm/page_hinting.c b/virt/kvm/page_hinting.c
index 818bd6b84e0c..4a34ea8db0c8 100644
--- a/virt/kvm/page_hinting.c
+++ b/virt/kvm/page_hinting.c
@@ -1,6 +1,7 @@
 #include <linux/gfp.h>
 #include <linux/mm.h>
 #include <linux/kernel.h>
+#include <linux/kvm_host.h>
 
 /*
  * struct kvm_free_pages - Tracks the pages which are freed by the guest.
@@ -31,6 +32,28 @@ struct page_hinting {
 
 DEFINE_PER_CPU(struct page_hinting, hinting_obj);
 
+struct static_key_false guest_page_hinting_key  = STATIC_KEY_FALSE_INIT;
+EXPORT_SYMBOL(guest_page_hinting_key);
+static DEFINE_MUTEX(hinting_mutex);
+int guest_page_hinting_flag;
+EXPORT_SYMBOL(guest_page_hinting_flag);
+
+int guest_page_hinting_sysctl(struct ctl_table *table, int write,
+			      void __user *buffer, size_t *lenp,
+			      loff_t *ppos)
+{
+	int ret;
+
+	mutex_lock(&hinting_mutex);
+	ret = proc_dointvec(table, write, buffer, lenp, ppos);
+	if (guest_page_hinting_flag)
+		static_key_enable(&guest_page_hinting_key.key);
+	else
+		static_key_disable(&guest_page_hinting_key.key);
+	mutex_unlock(&hinting_mutex);
+	return ret;
+}
+
 void guest_free_page(struct page *page, int order)
 {
 }
-- 
2.17.2