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Subject[RFC][Patch v8 1/7] KVM: Support for guest free page hinting
Date
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 <nitesh@redhat.com>
---
arch/x86/Kbuild | 2 +-
arch/x86/kvm/Kconfig | 8 ++++++++
arch/x86/kvm/Makefile | 2 ++
include/linux/gfp.h | 9 +++++++++
include/linux/page_hinting.h | 17 +++++++++++++++++
virt/kvm/page_hinting.c | 36 ++++++++++++++++++++++++++++++++++++
6 files changed, 73 insertions(+), 1 deletion(-)
create mode 100644 include/linux/page_hinting.h
create mode 100644 virt/kvm/page_hinting.c

diff --git a/arch/x86/Kbuild b/arch/x86/Kbuild
index c625f57472f7..3244df4ee311 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/Kconfig b/arch/x86/kvm/Kconfig
index 72fa955f4a15..2fae31459706 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -96,6 +96,14 @@ config KVM_MMU_AUDIT
This option adds a R/W kVM module parameter 'mmu_audit', which allows
auditing of KVM MMU events at runtime.

+# KVM_FREE_PAGE_HINTING will allow the guest to report the free pages to the
+# host in regular interval of time.
+config KVM_FREE_PAGE_HINTING
+ def_bool y
+ depends on KVM
+ select VIRTIO
+ select VIRTIO_BALLOON
+
# OK, it's a little counter-intuitive to do this, but it puts it neatly under
# the virtualization menu.
source "drivers/vhost/Kconfig"
diff --git a/arch/x86/kvm/Makefile b/arch/x86/kvm/Makefile
index 69b3a7c30013..78640a80501e 100644
--- a/arch/x86/kvm/Makefile
+++ b/arch/x86/kvm/Makefile
@@ -16,6 +16,8 @@ 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/vmx.o vmx/vmenter.o vmx/pmu_intel.o vmx/vmcs12.o vmx/evmcs.o vmx/nested.o
kvm-amd-y += svm.o pmu_amd.o

diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 5f5e25fd6149..e596527284ba 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -7,6 +7,7 @@
#include <linux/stddef.h>
#include <linux/linkage.h>
#include <linux/topology.h>
+#include <linux/page_hinting.h>

struct vm_area_struct;

@@ -456,6 +457,14 @@ 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_FREE_PAGE
+static inline void arch_free_page(struct page *page, int order)
+{
+ guest_free_page(page, order);
+}
+#endif
+
#ifndef HAVE_ARCH_FREE_PAGE
static inline void arch_free_page(struct page *page, int order) { }
#endif
diff --git a/include/linux/page_hinting.h b/include/linux/page_hinting.h
new file mode 100644
index 000000000000..b54f7428f348
--- /dev/null
+++ b/include/linux/page_hinting.h
@@ -0,0 +1,17 @@
+/*
+ * Size of the array which is used to store the freed pages is defined by
+ * MAX_FGPT_ENTRIES. If possible, we have to find a better way using which
+ * we can get rid of the hardcoded array size.
+ */
+#define MAX_FGPT_ENTRIES 1000
+/*
+ * hypervisor_pages - It is a dummy structure passed with the hypercall.
+ * @pfn: page frame number for the page which needs to be sent to the host.
+ * @order: order of the page needs to be reported to the host.
+ */
+struct hypervisor_pages {
+ unsigned long pfn;
+ unsigned int order;
+};
+
+void guest_free_page(struct page *page, int order);
diff --git a/virt/kvm/page_hinting.c b/virt/kvm/page_hinting.c
new file mode 100644
index 000000000000..818bd6b84e0c
--- /dev/null
+++ b/virt/kvm/page_hinting.c
@@ -0,0 +1,36 @@
+#include <linux/gfp.h>
+#include <linux/mm.h>
+#include <linux/kernel.h>
+
+/*
+ * struct kvm_free_pages - Tracks the pages which are freed by the guest.
+ * @pfn: page frame number for the page which is freed.
+ * @order: order corresponding to the page freed.
+ * @zonenum: zone number to which the freed page belongs.
+ */
+struct kvm_free_pages {
+ unsigned long pfn;
+ unsigned int order;
+ int zonenum;
+};
+
+/*
+ * struct page_hinting - holds array objects for the structures used to track
+ * guest free pages, along with an index variable for each of them.
+ * @kvm_pt: array object for the structure kvm_free_pages.
+ * @kvm_pt_idx: index for kvm_free_pages object.
+ * @hypervisor_pagelist: array object for the structure hypervisor_pages.
+ * @hyp_idx: index for hypervisor_pages object.
+ */
+struct page_hinting {
+ struct kvm_free_pages kvm_pt[MAX_FGPT_ENTRIES];
+ int kvm_pt_idx;
+ struct hypervisor_pages hypervisor_pagelist[MAX_FGPT_ENTRIES];
+ int hyp_idx;
+};
+
+DEFINE_PER_CPU(struct page_hinting, hinting_obj);
+
+void guest_free_page(struct page *page, int order)
+{
+}
--
2.17.2
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