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@xxxxxxxxxx>
---
Documentation/sysctl/vm.txt | 12 ++++++++++++
drivers/virtio/virtio_balloon.c | 4 ++++
include/linux/page_hinting.h | 5 +++++
kernel/sysctl.c | 12 ++++++++++++
virt/kvm/page_hinting.c | 26 ++++++++++++++++++++++++++
5 files changed, 59 insertions(+)
diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt
index 187ce4f599a2..eae9180ea0aa 100644
--- a/Documentation/sysctl/vm.txt
+++ b/Documentation/sysctl/vm.txt
@@ -31,6 +31,7 @@ Currently, these files are in /proc/sys/vm:
- dirty_writeback_centisecs
- drop_caches
- extfrag_threshold
+- guest_free_page_hinting
- hugetlb_shm_group
- laptop_mode
- legacy_va_layout
@@ -255,6 +256,17 @@ fragmentation index is <= extfrag_threshold. The default value is 500.
==============================================================
+guest_free_page_hinting
+
+This parameter enables the kernel to report KVM guest free pages to the host
+via virtio balloon driver. QEMU receives these free page hints and frees them
+by performing MADVISE_DONTNEED on it.
+
+It depends on VIRTIO_BALLOON for its functionality. In case VIRTIO_BALLOON
+driver is missing, this feature is disabled by default.
+
+==============================================================
+
highmem_is_dirtyable
Available only for systems with CONFIG_HIGHMEM enabled (32b systems).
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index e82c72cd916b..171fd72ef2ae 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -164,12 +164,16 @@ static void hinting_ack(struct virtqueue *vq)
static void enable_hinting(struct virtio_balloon *vb)
{
+ guest_free_page_hinting_flag = 1;
+ static_branch_enable(&guest_free_page_hinting_key);
request_hypercall = (void *)&virtballoon_page_hinting;
balloon_ptr = vb;
}
static void disable_hinting(void)
{
+ guest_free_page_hinting_flag = 0;
+ static_branch_enable(&guest_free_page_hinting_key);
balloon_ptr = NULL;
}
#endif
diff --git a/include/linux/page_hinting.h b/include/linux/page_hinting.h
index a32af8851081..60e0a21bfbe6 100644
--- a/include/linux/page_hinting.h
+++ b/include/linux/page_hinting.h
@@ -12,6 +12,8 @@
#define FREE_PAGE_HINTING_MIN_ORDER (MAX_ORDER - 1)
extern void *balloon_ptr;
+extern int guest_free_page_hinting_flag;
+extern struct static_key_false guest_free_page_hinting_key;
void guest_free_page_enqueue(struct page *page, int order);
void guest_free_page_try_hinting(void);
@@ -22,3 +24,6 @@ extern void __free_one_page(struct page *page, unsigned long pfn,
void release_buddy_pages(void *obj_to_free, int entries);
extern int (*request_hypercall)(void *balloon_ptr,
void *hinting_req, int entries);
+int guest_free_page_hinting_sysctl(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp,
+ loff_t *ppos);
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index ba4d9e85feb8..7b2970e9e937 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -96,6 +96,9 @@
#ifdef CONFIG_LOCKUP_DETECTOR
#include <linux/nmi.h>
#endif
+#ifdef CONFIG_KVM_FREE_PAGE_HINTING
+#include <linux/page_hinting.h>
+#endif
#if defined(CONFIG_SYSCTL)
@@ -1690,6 +1693,15 @@ 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-free-page-hinting",
+ .data = &guest_free_page_hinting_flag,
+ .maxlen = sizeof(guest_free_page_hinting_flag),
+ .mode = 0644,
+ .proc_handler = guest_free_page_hinting_sysctl,
+ },
#endif
{ }
};
diff --git a/virt/kvm/page_hinting.c b/virt/kvm/page_hinting.c
index eb0c0ddfe990..5980682e0b86 100644
--- a/virt/kvm/page_hinting.c
+++ b/virt/kvm/page_hinting.c
@@ -36,6 +36,28 @@ EXPORT_SYMBOL(request_hypercall);
void *balloon_ptr;
EXPORT_SYMBOL(balloon_ptr);
+struct static_key_false guest_free_page_hinting_key = STATIC_KEY_FALSE_INIT;
+EXPORT_SYMBOL(guest_free_page_hinting_key);
+static DEFINE_MUTEX(hinting_mutex);
+int guest_free_page_hinting_flag;
+EXPORT_SYMBOL(guest_free_page_hinting_flag);
+
+int guest_free_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_free_page_hinting_flag)
+ static_key_enable(&guest_free_page_hinting_key.key);
+ else
+ static_key_disable(&guest_free_page_hinting_key.key);
+ mutex_unlock(&hinting_mutex);
+ return ret;
+}
+
void release_buddy_pages(void *hinting_req, int entries)
{
int i = 0;
@@ -223,6 +245,8 @@ void guest_free_page_enqueue(struct page *page, int order)
struct guest_free_pages *hinting_obj;
int l_idx;
+ if (!static_branch_unlikely(&guest_free_page_hinting_key))
+ return;
/*
* use of global variables may trigger a race condition between irq and
* process context causing unwanted overwrites. This will be replaced
@@ -258,6 +282,8 @@ void guest_free_page_try_hinting(void)
{
struct guest_free_pages *hinting_obj;
+ if (!static_branch_unlikely(&guest_free_page_hinting_key))
+ return;
hinting_obj = this_cpu_ptr(&free_pages_obj);
if (hinting_obj->free_pages_idx >= HINTING_THRESHOLD)
guest_free_page_hinting();
--
2.17.2
