[Patch v4 1/6] KVM: Support for guest page hinting

[nilal@redhat.com]

From: Nitesh Narayan Lal <nilal@redhat.com>

This patch includes the following:
1. Basic skeleton for the support
2. Enablement of x86 platform to use the same

Signed-off-by: Nitesh Narayan Lal <nilal@redhat.com>
---
 arch/x86/Kbuild         |  2 +-
 arch/x86/kvm/Makefile   |  2 ++
 include/linux/gfp.h     |  7 +++++++
 virt/kvm/Kconfig        |  4 ++++
 virt/kvm/page_hinting.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 60 insertions(+), 1 deletion(-)
 create mode 100644 virt/kvm/page_hinting.c

diff --git a/arch/x86/Kbuild b/arch/x86/Kbuild
index 0038a2d..7d39d7d 100644
--- a/arch/x86/Kbuild
+++ b/arch/x86/Kbuild
@@ -2,7 +2,7 @@ obj-y += entry/
 
 obj-$(CONFIG_PERF_EVENTS) += events/
 
-obj-$(CONFIG_KVM) += kvm/
+obj-$(subst m,y,$(CONFIG_KVM)) += kvm/
 
 # Xen paravirtualization support
 obj-$(CONFIG_XEN) += xen/
diff --git a/arch/x86/kvm/Makefile b/arch/x86/kvm/Makefile
index 09d4b17..d8a3800 100644
--- a/arch/x86/kvm/Makefile
+++ b/arch/x86/kvm/Makefile
@@ -15,6 +15,8 @@ kvm-y			+= x86.o mmu.o emulate.o i8259.o irq.o lapic.o \
 			   i8254.o ioapic.o irq_comm.o cpuid.o pmu.o mtrr.o \
 			   hyperv.o page_track.o debugfs.o
 
+obj-$(CONFIG_KVM_FREE_PAGE_HINTING)	+= $(KVM)/page_hinting.o
+
 kvm-intel-y		+= vmx.o pmu_intel.o
 kvm-amd-y		+= svm.o pmu_amd.o
 
diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index f780718..a74371f 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -452,6 +452,13 @@ static inline struct zonelist *node_zonelist(int nid, gfp_t flags)
 	return NODE_DATA(nid)->node_zonelists + gfp_zonelist(flags);
 }
 
+#ifdef	CONFIG_KVM_FREE_PAGE_HINTING
+#define HAVE_ARCH_ALLOC_PAGE
+#define HAVE_ARCH_FREE_PAGE
+void arch_free_page(struct page *page, int order);
+void arch_alloc_page(struct page *page, int order);
+#endif
+
 #ifndef HAVE_ARCH_FREE_PAGE
 static inline void arch_free_page(struct page *page, int order) { }
 #endif
diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
index b0cc1a3..936c71d 100644
--- a/virt/kvm/Kconfig
+++ b/virt/kvm/Kconfig
@@ -50,3 +50,7 @@ config KVM_COMPAT
 
 config HAVE_KVM_IRQ_BYPASS
        bool
+
+config KVM_FREE_PAGE_HINTING
+       def_bool y
+       depends on KVM
diff --git a/virt/kvm/page_hinting.c b/virt/kvm/page_hinting.c
new file mode 100644
index 0000000..39d2b1d
--- /dev/null
+++ b/virt/kvm/page_hinting.c
@@ -0,0 +1,46 @@
+#include <linux/gfp.h>
+#include <linux/mm.h>
+#include <linux/page_ref.h>
+#include <linux/kvm_host.h>
+#include <linux/sort.h>
+
+#include <trace/events/kvm.h>
+
+#define MAX_FGPT_ENTRIES	1000
+#define HYPERLIST_THRESHOLD	500
+/*
+ * struct kvm_free_pages - Tracks the pages which are freed by the guest.
+ * @pfn	- page frame number for the page which is to be freed
+ * @pages - number of pages which are supposed to be freed.
+ * A global array object is used to hold the list of pfn and number of pages
+ * which are freed by the guest. This list may also have fragmentated pages so
+ * defragmentation is a must prior to the hypercall.
+ */
+struct kvm_free_pages {
+	unsigned long pfn;
+	unsigned int pages;
+};
+
+/*
+ * hypervisor_pages - It is a dummy structure passed with the hypercall.
+ * @pfn - page frame number for the page which is to be freed.
+ * @pages - number of pages which are supposed to be freed.
+ * A global array object is used to to hold the list of pfn and pages and is
+ * passed as part of the hypercall.
+ */
+struct hypervisor_pages {
+	unsigned long pfn;
+	unsigned int pages;
+};
+
+DEFINE_PER_CPU(struct kvm_free_pages [MAX_FGPT_ENTRIES], kvm_pt);
+DEFINE_PER_CPU(int, kvm_pt_idx);
+struct hypervisor_pages hypervisor_pagelist[MAX_FGPT_ENTRIES];
+
+void arch_alloc_page(struct page *page, int order)
+{
+}
+
+void arch_free_page(struct page *page, int order)
+{
+}
-- 
2.9.4