[RFC 2/2] kvm: guest-side changes for tmem on KVM

[Akshay Karle <akshay.a.karle@gmail.com>]

From: Akshay Karle <akshay.a.karle@gmail.com>
Subject: [RFC 2/2] kvm: guest-side changes for tmem on KVM

Working in the guest:
At the kvm guest, we add the appropriate tmem shims to intercept the
tmem operations and then invoke the kvm hypercalls to exit to the host
and perform these operations.

Signed-off-by: Akshay Karle <akshay.a.karle@gmail.com>

---
Diffstat for guest side changes:
 drivers/staging/zcache/Makefile   |    2 
 drivers/staging/zcache/kvm-tmem.c |  356 ++++++++++++++++++++++++++++++++++++++
 drivers/staging/zcache/kvm-tmem.h |   55 +++++
 include/linux/kvm_para.h          |    1 
 4 files changed, 413 insertions(+), 1 deletion(-)

diff -Napur vanilla/linux-3.1.5/drivers/staging/zcache/kvm-tmem.c linux-3.1.5//drivers/staging/zcache/kvm-tmem.c
--- vanilla/linux-3.1.5/drivers/staging/zcache/kvm-tmem.c	1970-01-01 05:30:00.000000000 +0530
+++ linux-3.1.5//drivers/staging/zcache/kvm-tmem.c	2012-03-05 14:16:00.892007167 +0530
@@ -0,0 +1,356 @@
+/*
+ * kvm implementation for transcendent memory (tmem)
+ *
+ * Copyright (C) 2009-2011 Oracle Corp.  All rights reserved.
+ * Author: Dan Magenheimer
+ *	   Akshay Karle
+ *	   Ashutosh Tripathi
+ *	   Nishant Gulhane
+ *	   Shreyas Mahure
+ */
+
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/init.h>
+#include <linux/pagemap.h>
+#include <linux/module.h>
+#include <linux/cleancache.h>
+
+/* temporary ifdef until include/linux/frontswap.h is upstream */
+#ifdef CONFIG_FRONTSWAP
+#include <linux/frontswap.h>
+#endif
+
+#include "kvm-tmem.h"
+
+/* kvm tmem foundation ops/hypercalls */
+
+static inline int kvm_tmem_op(u32 tmem_cmd, u32 tmem_pool, struct tmem_oid oid,
+	u32 index, u32 tmem_offset, u32 pfn_offset, unsigned long pfn, u32 len, uint16_t cli_id)
+{
+	struct tmem_ops op;
+	int rc = 0;
+	op.cmd = tmem_cmd;
+	op.pool_id = tmem_pool;
+	op.u.gen.oid[0] = oid.oid[0];
+	op.u.gen.oid[1] = oid.oid[1];
+	op.u.gen.oid[2] = oid.oid[2];
+	op.u.gen.index = index;
+	op.u.gen.tmem_offset = tmem_offset;
+	op.u.gen.pfn_offset = pfn_offset;
+	op.u.gen.pfn = pfn;
+	op.u.gen.len = len;
+	op.u.gen.cli_id = cli_id;
+	rc = kvm_hypercall1(KVM_HC_TMEM, virt_to_phys(&op));
+	rc = rc + 1000;
+	return rc;
+}
+
+static int kvm_tmem_new_pool(uint16_t cli_id,
+				u32 flags, unsigned long pagesize)
+{
+	struct tmem_ops op;
+	int rc, pageshift;
+	for (pageshift = 0; pagesize != 1; pageshift++)
+		pagesize >>= 1;
+	flags |= (pageshift - 12) << TMEM_POOL_PAGESIZE_SHIFT;
+	flags |= TMEM_SPEC_VERSION << TMEM_VERSION_SHIFT;
+	op.cmd = TMEM_NEW_POOL;
+	op.u.new.cli_id = cli_id;
+	op.u.new.flags = flags;
+	rc = kvm_hypercall1(KVM_HC_TMEM, virt_to_phys(&op));
+	rc = rc + 1000;
+	return rc;
+}
+
+/* kvm generic tmem ops */
+
+static int kvm_tmem_put_page(u32 pool_id, struct tmem_oid oid,
+			     u32 index, unsigned long pfn)
+{
+
+	return kvm_tmem_op(TMEM_PUT_PAGE, pool_id, oid, index,
+		0, 0, pfn, 0, TMEM_CLI);
+}
+
+static int kvm_tmem_get_page(u32 pool_id, struct tmem_oid oid,
+			     u32 index, unsigned long pfn)
+{
+
+	return kvm_tmem_op(TMEM_GET_PAGE, pool_id, oid, index,
+		0, 0, pfn, 0, TMEM_CLI);
+}
+
+static int kvm_tmem_flush_page(u32 pool_id, struct tmem_oid oid, u32 index)
+{
+	return kvm_tmem_op(TMEM_FLUSH_PAGE, pool_id, oid, index,
+		0, 0, 0, 0, TMEM_CLI);
+}
+
+static int kvm_tmem_flush_object(u32 pool_id, struct tmem_oid oid)
+{
+	return kvm_tmem_op(TMEM_FLUSH_OBJECT, pool_id, oid, 0, 0, 0, 0, 0, TMEM_CLI);
+}
+
+static int kvm_tmem_destroy_pool(u32 pool_id)
+{
+	struct tmem_oid oid = { { 0 } };
+
+	return kvm_tmem_op(TMEM_DESTROY_POOL, pool_id, oid, 0, 0, 0, 0, 0, TMEM_CLI);
+}
+
+static int kvm_tmem_enabled;
+
+static int __init enable_tmem_kvm(char *s)
+{
+	kvm_tmem_enabled = 1;
+	return 1;
+}
+__setup("tmem", enable_tmem_kvm);
+
+/* cleancache ops */
+
+#ifdef CONFIG_CLEANCACHE
+static void tmem_cleancache_put_page(int pool, struct cleancache_filekey key,
+				     pgoff_t index, struct page *page)
+{
+	u32 ind = (u32) index;
+	struct tmem_oid oid = *(struct tmem_oid *)&key;
+	unsigned long pfn = page_to_pfn(page);
+
+	if (pool < 0)
+		return;
+	if (ind != index)
+		return;
+	mb(); /* ensure page is quiescent; tmem may address it with an alias */
+	(void)kvm_tmem_put_page((u32)pool, oid, ind, pfn);
+}
+
+static int tmem_cleancache_get_page(int pool, struct cleancache_filekey key,
+				    pgoff_t index, struct page *page)
+{
+	u32 ind = (u32) index;
+	struct tmem_oid oid = *(struct tmem_oid *)&key;
+	unsigned long pfn = page_to_pfn(page);
+	int ret;
+
+	/* translate return values to linux semantics */
+	if (pool < 0)
+		return -1;
+	if (ind != index)
+		return -1;
+	ret = kvm_tmem_get_page((u32)pool, oid, ind, pfn);
+	return ret;
+}
+
+static void tmem_cleancache_flush_page(int pool, struct cleancache_filekey key,
+				       pgoff_t index)
+{
+	u32 ind = (u32) index;
+	struct tmem_oid oid = *(struct tmem_oid *)&key;
+
+	if (pool < 0)
+		return;
+	if (ind != index)
+		return;
+	(void)kvm_tmem_flush_page((u32)pool, oid, ind);
+}
+
+static void tmem_cleancache_flush_inode(int pool, struct cleancache_filekey key)
+{
+	struct tmem_oid oid = *(struct tmem_oid *)&key;
+
+	if (pool < 0)
+		return;
+	(void)kvm_tmem_flush_object((u32)pool, oid);
+}
+
+static void tmem_cleancache_flush_fs(int pool)
+{
+	if (pool < 0)
+		return;
+	(void)kvm_tmem_destroy_pool((u32)pool);
+}
+
+static int tmem_cleancache_init_fs(size_t pagesize)
+{
+	uint16_t cli_id=TMEM_CLI;
+	return kvm_tmem_new_pool(cli_id, 0, pagesize);
+}
+
+static int tmem_cleancache_init_shared_fs(char *uuid, size_t pagesize)
+{
+	uint16_t cli_id=TMEM_CLI;
+	return kvm_tmem_new_pool(cli_id, TMEM_POOL_SHARED, pagesize);
+}
+
+static int use_cleancache = 1;
+
+static int __init no_cleancache(char *s)
+{
+	use_cleancache = 0;
+	return 1;
+}
+
+__setup("nocleancache", no_cleancache);
+
+static struct cleancache_ops tmem_cleancache_ops = {
+	.put_page = tmem_cleancache_put_page,
+	.get_page = tmem_cleancache_get_page,
+	.flush_page = tmem_cleancache_flush_page,
+	.flush_inode = tmem_cleancache_flush_inode,
+	.flush_fs = tmem_cleancache_flush_fs,
+	.init_shared_fs = tmem_cleancache_init_shared_fs,
+	.init_fs = tmem_cleancache_init_fs
+};
+#endif
+
+#ifdef CONFIG_FRONTSWAP
+/* frontswap tmem operations */
+
+/* a single tmem poolid is used for all frontswap "types" (swapfiles) */
+static int tmem_frontswap_poolid;
+
+/*
+ * Swizzling increases objects per swaptype, increasing tmem concurrency
+ * for heavy swaploads.  Later, larger nr_cpus -> larger SWIZ_BITS
+ */
+#define SWIZ_BITS		4
+#define SWIZ_MASK		((1 << SWIZ_BITS) - 1)
+#define _oswiz(_type, _ind)	((_type << SWIZ_BITS) | (_ind & SWIZ_MASK))
+#define iswiz(_ind)		(_ind >> SWIZ_BITS)
+
+static inline struct tmem_oid oswiz(unsigned type, u32 ind)
+{
+	struct tmem_oid oid = { .oid = { 0 } };
+	oid.oid[0] = _oswiz(type, ind);
+	return oid;
+}
+
+/* returns 0 if the page was successfully put into frontswap, -1 if not */
+static int tmem_frontswap_put_page(unsigned type, pgoff_t offset,
+				   struct page *page)
+{
+	u64 ind64 = (u64)offset;
+	u32 ind = (u32)offset;
+	unsigned long pfn = page_to_pfn(page);
+	int pool = tmem_frontswap_poolid;
+	int ret;
+
+	if (pool < 0)
+		return -1;
+	if (ind64 != ind)
+		return -1;
+	mb(); /* ensure page is quiescent; tmem may address it with an alias */
+	ret = kvm_tmem_put_page(pool, oswiz(type, ind), iswiz(ind), pfn);
+	/* translate kvm tmem return values to linux semantics */
+	return ret;
+}
+
+/*
+ * returns 0 if the page was successfully gotten from frontswap, -1 if
+ * was not present (should never happen!)
+ */
+static int tmem_frontswap_get_page(unsigned type, pgoff_t offset,
+				   struct page *page)
+{
+	u64 ind64 = (u64)offset;
+	u32 ind = (u32)offset;
+	unsigned long pfn = page_to_pfn(page);
+	int pool = tmem_frontswap_poolid;
+	int ret;
+
+	if (pool < 0)
+		return -1;
+	if (ind64 != ind)
+		return -1;
+	ret = kvm_tmem_get_page(pool, oswiz(type, ind), iswiz(ind), pfn);
+	/* translate kvm tmem return values to linux semantics */
+	return ret;
+}
+
+/* flush a single page from frontswap */
+static void tmem_frontswap_flush_page(unsigned type, pgoff_t offset)
+{
+	u64 ind64 = (u64)offset;
+	u32 ind = (u32)offset;
+	int pool = tmem_frontswap_poolid;
+
+	if (pool < 0)
+		return;
+	if (ind64 != ind)
+		return;
+	(void) kvm_tmem_flush_page(pool, oswiz(type, ind), iswiz(ind));
+}
+
+/* flush all pages from the passed swaptype */
+static void tmem_frontswap_flush_area(unsigned type)
+{
+	int pool = tmem_frontswap_poolid;
+	int ind;
+
+	if (pool < 0)
+		return;
+	for (ind = SWIZ_MASK; ind >= 0; ind--)
+		(void)kvm_tmem_flush_object(pool, oswiz(type, ind));
+	(void)kvm_tmem_destroy_pool((u32)pool);
+}
+
+static void tmem_frontswap_init(unsigned ignored)
+{
+	/* a single tmem poolid is used for all frontswap "types" (swapfiles) */
+	if (tmem_frontswap_poolid < 0)
+		tmem_frontswap_poolid =
+		    kvm_tmem_new_pool(TMEM_CLI, TMEM_POOL_PERSIST, PAGE_SIZE);
+}
+
+static int __initdata use_frontswap = 1;
+
+static int __init no_frontswap(char *s)
+{
+	use_frontswap = 0;
+	return 1;
+}
+
+__setup("nofrontswap", no_frontswap);
+
+static struct frontswap_ops tmem_frontswap_ops = {
+	.put_page = tmem_frontswap_put_page,
+	.get_page = tmem_frontswap_get_page,
+	.flush_page = tmem_frontswap_flush_page,
+	.flush_area = tmem_frontswap_flush_area,
+	.init = tmem_frontswap_init
+};
+#endif
+
+static int __init kvm_tmem_init(void)
+{
+#ifdef CONFIG_FRONTSWAP
+	if (kvm_tmem_enabled && use_frontswap) {
+		char *s = "";
+		struct frontswap_ops old_ops =
+			frontswap_register_ops(&tmem_frontswap_ops);
+
+		tmem_frontswap_poolid = -1;
+		if (old_ops.init != NULL)
+			s = " (WARNING: frontswap_ops overridden)";
+		printk(KERN_INFO "%% frontswap enabled, RAM provided by "
+				 "kvm Transcendent Memory\n");
+	}
+#endif
+#ifdef CONFIG_CLEANCACHE
+	BUG_ON(sizeof(struct cleancache_filekey) != sizeof(struct tmem_oid));
+	if (kvm_tmem_enabled && use_cleancache) {
+		char *s = "";
+		struct cleancache_ops old_ops =
+			cleancache_register_ops(&tmem_cleancache_ops);
+		if (old_ops.init_fs != NULL)
+			s = " (WARNING: cleancache_ops overridden)";
+		printk(KERN_INFO "%% cleancache enabled, RAM provided by "
+				 "kvm Transcendent Memory%s\n", s);
+	}
+#endif
+	return 0;
+}
+
+module_init(kvm_tmem_init)
diff -Napur vanilla/linux-3.1.5/drivers/staging/zcache/kvm-tmem.h linux-3.1.5//drivers/staging/zcache/kvm-tmem.h
--- vanilla/linux-3.1.5/drivers/staging/zcache/kvm-tmem.h	1970-01-01 05:30:00.000000000 +0530
+++ linux-3.1.5//drivers/staging/zcache/kvm-tmem.h	2012-03-05 14:16:00.892007167 +0530
@@ -0,0 +1,55 @@
+#ifndef _TMEM_H
+#define _TMEM_H
+
+#include <linux/types.h>
+#include <linux/kvm_host.h>
+#include <linux/kvm_types.h>
+#include <linux/kvm_para.h>
+#include "tmem.h"
+
+#define TMEM_SPEC_VERSION 1
+#define TMEM_CLI	  1
+
+/* Different tmem ops */
+#define TMEM_CONTROL               0
+#define TMEM_NEW_POOL              1
+#define TMEM_DESTROY_POOL          2
+#define TMEM_NEW_PAGE              3
+#define TMEM_PUT_PAGE              4
+#define TMEM_GET_PAGE              5
+#define TMEM_FLUSH_PAGE            6
+#define TMEM_FLUSH_OBJECT          7
+#define TMEM_READ                  8
+#define TMEM_WRITE                 9
+#define TMEM_XCHG                 10
+
+/* Bits for kvm_hypercall1(TMEM_NEW_POOL) */
+#define TMEM_POOL_PERSIST          1
+#define TMEM_POOL_SHARED           2
+#define TMEM_POOL_PAGESIZE_SHIFT   4
+#define TMEM_VERSION_SHIFT        24
+
+/* flags for tmem_ops.new_pool */
+#define TMEM_POOL_PERSIST          1
+#define TMEM_POOL_SHARED           2
+
+struct tmem_ops {
+        uint32_t cmd;
+        int32_t pool_id;
+        union {
+                struct {  /* for cmd == TMEM_NEW_POOL */
+                        uint16_t cli_id;
+                        uint32_t flags;
+                } new;
+                struct {
+                        uint64_t oid[3];
+                        uint32_t index;
+                        uint32_t tmem_offset;
+                        uint32_t pfn_offset;
+                        uint32_t pfn;
+                        uint32_t len;
+			uint16_t cli_id;
+                } gen;
+        } u;
+};
+#endif
diff -Napur vanilla/linux-3.1.5/drivers/staging/zcache/Makefile linux-3.1.5//drivers/staging/zcache/Makefile
--- vanilla/linux-3.1.5/drivers/staging/zcache/Makefile	2011-12-09 22:27:05.000000000 +0530
+++ linux-3.1.5//drivers/staging/zcache/Makefile	2012-03-05 14:16:00.892007167 +0530
@@ -1,3 +1,3 @@
-zcache-y	:=	zcache-main.o tmem.o
+zcache-y	:=	zcache-main.o tmem.o kvm-tmem.o
 
 obj-$(CONFIG_ZCACHE)	+=	zcache.o
diff -Napur vanilla/linux-3.1.5/include/linux/kvm_para.h linux-3.1.5//include/linux/kvm_para.h
--- vanilla/linux-3.1.5/include/linux/kvm_para.h	2011-12-09 22:27:05.000000000 +0530
+++ linux-3.1.5//include/linux/kvm_para.h	2012-03-05 14:16:00.892007167 +0530
@@ -19,6 +19,7 @@
 #define KVM_HC_MMU_OP			2
 #define KVM_HC_FEATURES			3
 #define KVM_HC_PPC_MAP_MAGIC_PAGE	4
+#define KVM_HC_TMEM			5
 
 /*
  * hypercalls use architecture specific