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[Xen-devel] Re: [PATCH 10/15] xen: Introduce the Xen mapcache
On 08/12/2010 09:09 AM, stefano.stabellini@xxxxxxxxxxxxx wrote:
From: Anthony PERARD<anthony.perard@xxxxxxxxxx>
Introduce a mapcache to handle the 64bit address space of the guest
from a 32bit userland process (Qemu).
The mapcache maps chucks of guest memory on demand, unmaps them when
they are not needed anymore.
Signed-off-by: Anthony PERARD<anthony.perard@xxxxxxxxxx>
Signed-off-by: Stefano Stabellini<stefano.stabellini@xxxxxxxxxxxxx>
---
hw/xen_machine_fv.c | 7 ++
target-xen/qemu-xen.h | 15 +++
target-xen/xen_mapcache.c | 233 +++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 255 insertions(+), 0 deletions(-)
diff --git a/hw/xen_machine_fv.c b/hw/xen_machine_fv.c
index b1bc88d..58237d6 100644
--- a/hw/xen_machine_fv.c
+++ b/hw/xen_machine_fv.c
@@ -84,6 +84,13 @@ static void xen_init_fv(ram_addr_t ram_size,
exit(1);
}
+#if defined(__i386__) || defined(__x86_64__)
+ if (qemu_map_cache_init()) {
+ fprintf(stderr, "qemu_map_cache_init returned: error %d\n", errno);
+ exit(-1);
+ }
+#endif
+
xc_get_hvm_param(xen_xc, xen_domid, HVM_PARAM_IOREQ_PFN,&ioreq_pfn);
fprintf(stderr, "shared page at pfn %lx\n", ioreq_pfn);
shared_page = xc_map_foreign_range(xen_xc, xen_domid, XC_PAGE_SIZE,
diff --git a/target-xen/qemu-xen.h b/target-xen/qemu-xen.h
index 79a4638..e4a7030 100644
--- a/target-xen/qemu-xen.h
+++ b/target-xen/qemu-xen.h
@@ -13,6 +13,21 @@
/* xen_mapcache.c */
+#if (defined(__i386__) || defined(__x86_64__))&& !defined(QEMU_TOOL)
+#define MAPCACHE
+
+#if defined(__i386__)
+#define MAX_MCACHE_SIZE 0x40000000 /* 1GB max for x86 */
+#define MCACHE_BUCKET_SHIFT 16
+#elif defined(__x86_64__)
+#define MAX_MCACHE_SIZE 0x1000000000 /* 64GB max for x86_64 */
+#define MCACHE_BUCKET_SHIFT 20
+#endif
+
+#define MCACHE_BUCKET_SIZE (1UL<< MCACHE_BUCKET_SHIFT)
+#endif
+
+int qemu_map_cache_init(void);
uint8_t *qemu_map_cache(target_phys_addr_t phys_addr, uint8_t lock);
void qemu_invalidate_entry(uint8_t *buffer);
void qemu_invalidate_map_cache(void);
diff --git a/target-xen/xen_mapcache.c b/target-xen/xen_mapcache.c
index 39daae2..efe036c 100644
--- a/target-xen/xen_mapcache.c
+++ b/target-xen/xen_mapcache.c
@@ -1,5 +1,237 @@
+#include "config.h"
+
+#include "hw/xen_backend.h"
#include "qemu-xen.h"
+#include<xen/hvm/params.h>
+#include<sys/mman.h>
+
+#if defined(MAPCACHE)
+
+#define BITS_PER_LONG (sizeof(long)*8)
+#define BITS_TO_LONGS(bits) \
+ (((bits)+BITS_PER_LONG-1)/BITS_PER_LONG)
+#define DECLARE_BITMAP(name,bits) \
+ unsigned long name[BITS_TO_LONGS(bits)]
+#define test_bit(bit,map) \
+ (!!((map)[(bit)/BITS_PER_LONG]& (1UL<< ((bit)%BITS_PER_LONG))))
+
+struct map_cache {
+ unsigned long paddr_index;
+ uint8_t *vaddr_base;
+ DECLARE_BITMAP(valid_mapping, MCACHE_BUCKET_SIZE>>XC_PAGE_SHIFT);
+ uint8_t lock;
+ struct map_cache *next;
+};
+
+struct map_cache_rev {
+ uint8_t *vaddr_req;
+ unsigned long paddr_index;
+ QTAILQ_ENTRY(map_cache_rev) next;
+};
CODING_STYLE
+static struct map_cache *mapcache_entry;
+static unsigned long nr_buckets;
+QTAILQ_HEAD(map_cache_head, map_cache_rev) locked_entries =
QTAILQ_HEAD_INITIALIZER(locked_entries);
+
+/* For most cases (>99.9%), the page address is the same. */
+static unsigned long last_address_index = ~0UL;
+static uint8_t *last_address_vaddr;
Should refactor away global state.
+int qemu_map_cache_init(void)
+{
+ unsigned long size;
+
+ nr_buckets = (((MAX_MCACHE_SIZE>> XC_PAGE_SHIFT) +
+ (1UL<< (MCACHE_BUCKET_SHIFT - XC_PAGE_SHIFT)) - 1)>>
+ (MCACHE_BUCKET_SHIFT - XC_PAGE_SHIFT));
+
+ /*
+ * Use mmap() directly: lets us allocate a big hash table with no up-front
+ * cost in storage space. The OS will allocate memory only for the buckets
+ * that we actually use. All others will contain all zeroes.
+ */
+ size = nr_buckets * sizeof(struct map_cache);
+ size = (size + XC_PAGE_SIZE - 1)& ~(XC_PAGE_SIZE - 1);
+ fprintf(stderr, "qemu_map_cache_init nr_buckets = %lx size %lu\n",
nr_buckets, size);
+ mapcache_entry = mmap(NULL, size, PROT_READ|PROT_WRITE,
+ MAP_SHARED|MAP_ANON, -1, 0);
+ if (mapcache_entry == MAP_FAILED) {
+ errno = ENOMEM;
+ return -1;
+ }
+
+ return 0;
+}
+
+static void qemu_remap_bucket(struct map_cache *entry,
+ unsigned long address_index)
+{
+ uint8_t *vaddr_base;
+ xen_pfn_t pfns[MCACHE_BUCKET_SIZE>> XC_PAGE_SHIFT];
+ int err[MCACHE_BUCKET_SIZE>> XC_PAGE_SHIFT];
+ unsigned int i, j;
+
+ if (entry->vaddr_base != NULL) {
+ errno = munmap(entry->vaddr_base, MCACHE_BUCKET_SIZE);
+ if (errno) {
+ fprintf(stderr, "unmap fails %d\n", errno);
+ exit(-1);
+ }
+ }
+
+ for (i = 0; i< MCACHE_BUCKET_SIZE>> XC_PAGE_SHIFT; i++) {
+ pfns[i] = (address_index<< (MCACHE_BUCKET_SHIFT-XC_PAGE_SHIFT)) + i;
+ }
+
+ vaddr_base = xc_map_foreign_bulk(xen_xc, xen_domid, PROT_READ|PROT_WRITE,
+ pfns, err,
+ MCACHE_BUCKET_SIZE>> XC_PAGE_SHIFT);
+ if (vaddr_base == NULL) {
+ fprintf(stderr, "xc_map_foreign_bulk error %d\n", errno);
+ exit(-1);
+ }
+
+ entry->vaddr_base = vaddr_base;
+ entry->paddr_index = address_index;
+
+ for (i = 0; i< MCACHE_BUCKET_SIZE>> XC_PAGE_SHIFT; i += BITS_PER_LONG) {
+ unsigned long word = 0;
+ j = ((i + BITS_PER_LONG)> (MCACHE_BUCKET_SIZE>> XC_PAGE_SHIFT)) ?
+ (MCACHE_BUCKET_SIZE>> XC_PAGE_SHIFT) % BITS_PER_LONG :
BITS_PER_LONG;
+ while (j> 0) {
+ word = (word<< 1) | !err[i + --j];
+ }
+ entry->valid_mapping[i / BITS_PER_LONG] = word;
+ }
+}
+
+uint8_t *qemu_map_cache(target_phys_addr_t phys_addr, uint8_t lock)
+{
+ struct map_cache *entry, *pentry = NULL;
+ unsigned long address_index = phys_addr>> MCACHE_BUCKET_SHIFT;
+ unsigned long address_offset = phys_addr& (MCACHE_BUCKET_SIZE-1);
+
+ if (address_index == last_address_index&& !lock)
+ return last_address_vaddr + address_offset;
+
+ entry =&mapcache_entry[address_index % nr_buckets];
+
+ while (entry&& entry->lock&& entry->paddr_index != address_index&&
entry->vaddr_base) {
+ pentry = entry;
+ entry = entry->next;
+ }
+ if (!entry) {
+ entry = qemu_mallocz(sizeof(struct map_cache));
+ pentry->next = entry;
+ qemu_remap_bucket(entry, address_index);
+ } else if (!entry->lock) {
+ if (!entry->vaddr_base || entry->paddr_index != address_index ||
!test_bit(address_offset>>XC_PAGE_SHIFT, entry->valid_mapping))
+ qemu_remap_bucket(entry, address_index);
+ }
+
+ if (!test_bit(address_offset>>XC_PAGE_SHIFT, entry->valid_mapping)) {
+ last_address_index = ~0UL;
+ return NULL;
+ }
+
+ last_address_index = address_index;
+ last_address_vaddr = entry->vaddr_base;
+ if (lock) {
+ struct map_cache_rev *reventry = qemu_mallocz(sizeof(struct
map_cache_rev));
+ entry->lock++;
+ reventry->vaddr_req = last_address_vaddr + address_offset;
+ reventry->paddr_index = last_address_index;
+ QTAILQ_INSERT_TAIL(&locked_entries, reventry, next);
+ }
+
+ return last_address_vaddr + address_offset;
+}
+
+void qemu_invalidate_entry(uint8_t *buffer)
+{
+ struct map_cache *entry = NULL, *pentry = NULL;
+ struct map_cache_rev *reventry;
+ unsigned long paddr_index;
+ int found = 0;
+
+ if (last_address_vaddr == buffer)
+ last_address_index = ~0UL;
+
+ QTAILQ_FOREACH(reventry,&locked_entries, next) {
+ if (reventry->vaddr_req == buffer) {
+ paddr_index = reventry->paddr_index;
+ found = 1;
+ break;
+ }
+ }
+ if (!found) {
+ fprintf(stderr, "qemu_invalidate_entry: could not find %p\n", buffer);
+ QTAILQ_FOREACH(reventry,&locked_entries, next) {
+ fprintf(stderr, " %lx -> %p is present\n", reventry->paddr_index,
reventry->vaddr_req);
+ }
+ return;
+ }
+ QTAILQ_REMOVE(&locked_entries, reventry, next);
+ qemu_free(reventry);
+
+ entry =&mapcache_entry[paddr_index % nr_buckets];
+ while (entry&& entry->paddr_index != paddr_index) {
+ pentry = entry;
+ entry = entry->next;
+ }
+ if (!entry) {
+ fprintf(stderr, "Trying to unmap address %p that is not in the
mapcache!\n", buffer);
+ return;
+ }
+ entry->lock--;
+ if (entry->lock> 0 || pentry == NULL)
+ return;
+
+ pentry->next = entry->next;
+ errno = munmap(entry->vaddr_base, MCACHE_BUCKET_SIZE);
+ if (errno) {
+ fprintf(stderr, "unmap fails %d\n", errno);
+ exit(-1);
+ }
+ qemu_free(entry);
+}
+
+void qemu_invalidate_map_cache(void)
+{
+ unsigned long i;
+ struct map_cache_rev *reventry;
+
+ qemu_aio_flush();
+
+ QTAILQ_FOREACH(reventry,&locked_entries, next) {
+ fprintf(stderr, "There should be no locked mappings at this time, but %lx -> %p
is present\n", reventry->paddr_index, reventry->vaddr_req);
+ }
+
+ mapcache_lock();
+
+ for (i = 0; i< nr_buckets; i++) {
+ struct map_cache *entry =&mapcache_entry[i];
+
+ if (entry->vaddr_base == NULL)
+ continue;
+
+ errno = munmap(entry->vaddr_base, MCACHE_BUCKET_SIZE);
+ if (errno) {
+ fprintf(stderr, "unmap fails %d\n", errno);
+ exit(-1);
+ }
+
+ entry->paddr_index = 0;
+ entry->vaddr_base = NULL;
+ }
+
+ last_address_index = ~0UL;
+ last_address_vaddr = NULL;
+
+ mapcache_unlock();
+}
+#else
uint8_t *qemu_map_cache(target_phys_addr_t phys_addr, uint8_t lock)
{
return phys_ram_addr(phys_addr);
@@ -12,3 +244,4 @@ void qemu_invalidate_map_cache(void)
void qemu_invalidate_entry(uint8_t *buffer)
{
}
+#endif /* !MAPCACHE */
This should really tie into the RAMBlock infrastructure.
Regards,
Anthony Liguori
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