From: Paolo Bonzini <pbonzini@redhat.com>
To: qemu-devel@nongnu.org
Cc: "Philippe Mathieu-Daudé" <philmd@redhat.com>,
"Eduardo Habkost" <ehabkost@redhat.com>,
"Peter Xu" <peterx@redhat.com>,
"David Hildenbrand" <david@redhat.com>
Subject: [PULL 25/33] memory: Introduce RAM_NORESERVE and wire it up in qemu_ram_mmap()
Date: Tue, 15 Jun 2021 15:38:47 +0200 [thread overview]
Message-ID: <20210615133855.775687-26-pbonzini@redhat.com> (raw)
In-Reply-To: <20210615133855.775687-1-pbonzini@redhat.com>
From: David Hildenbrand <david@redhat.com>
Let's introduce RAM_NORESERVE, allowing mmap'ing with MAP_NORESERVE. The
new flag has the following semantics:
"
RAM is mmap-ed with MAP_NORESERVE. When set, reserving swap space (or huge
pages if applicable) is skipped: will bail out if not supported. When not
set, the OS will do the reservation, if supported for the memory type.
"
Allow passing it into:
- memory_region_init_ram_nomigrate()
- memory_region_init_resizeable_ram()
- memory_region_init_ram_from_file()
... and teach qemu_ram_mmap() and qemu_anon_ram_alloc() about the flag.
Bail out if the flag is not supported, which is the case right now for
both, POSIX and win32. We will add Linux support next and allow specifying
RAM_NORESERVE via memory backends.
The target use case is virtio-mem, which dynamically exposes memory
inside a large, sparse memory area to the VM.
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Acked-by: Eduardo Habkost <ehabkost@redhat.com> for memory backend and machine core
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20210510114328.21835-9-david@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
include/exec/cpu-common.h | 1 +
include/exec/memory.h | 15 ++++++++++++---
include/exec/ram_addr.h | 3 ++-
include/qemu/osdep.h | 9 ++++++++-
migration/ram.c | 3 +--
softmmu/physmem.c | 15 ++++++++++++---
util/mmap-alloc.c | 7 +++++++
util/oslib-posix.c | 6 ++++--
util/oslib-win32.c | 13 ++++++++++++-
9 files changed, 59 insertions(+), 13 deletions(-)
diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h
index ccabed4003..039d422bf4 100644
--- a/include/exec/cpu-common.h
+++ b/include/exec/cpu-common.h
@@ -59,6 +59,7 @@ ram_addr_t qemu_ram_get_offset(RAMBlock *rb);
ram_addr_t qemu_ram_get_used_length(RAMBlock *rb);
ram_addr_t qemu_ram_get_max_length(RAMBlock *rb);
bool qemu_ram_is_shared(RAMBlock *rb);
+bool qemu_ram_is_noreserve(RAMBlock *rb);
bool qemu_ram_is_uf_zeroable(RAMBlock *rb);
void qemu_ram_set_uf_zeroable(RAMBlock *rb);
bool qemu_ram_is_migratable(RAMBlock *rb);
diff --git a/include/exec/memory.h b/include/exec/memory.h
index b1f8fa1df0..b116f7c64e 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -155,6 +155,13 @@ typedef struct IOMMUTLBEvent {
*/
#define RAM_UF_WRITEPROTECT (1 << 6)
+/*
+ * RAM is mmap-ed with MAP_NORESERVE. When set, reserving swap space (or huge
+ * pages if applicable) is skipped: will bail out if not supported. When not
+ * set, the OS will do the reservation, if supported for the memory type.
+ */
+#define RAM_NORESERVE (1 << 7)
+
static inline void iommu_notifier_init(IOMMUNotifier *n, IOMMUNotify fn,
IOMMUNotifierFlag flags,
hwaddr start, hwaddr end,
@@ -949,7 +956,7 @@ void memory_region_init_ram_nomigrate(MemoryRegion *mr,
* @name: Region name, becomes part of RAMBlock name used in migration stream
* must be unique within any device
* @size: size of the region.
- * @ram_flags: RamBlock flags. Supported flags: RAM_SHARED.
+ * @ram_flags: RamBlock flags. Supported flags: RAM_SHARED, RAM_NORESERVE.
* @errp: pointer to Error*, to store an error if it happens.
*
* Note that this function does not do anything to cause the data in the
@@ -1005,7 +1012,8 @@ void memory_region_init_resizeable_ram(MemoryRegion *mr,
* @size: size of the region.
* @align: alignment of the region base address; if 0, the default alignment
* (getpagesize()) will be used.
- * @ram_flags: RamBlock flags. Supported flags: RAM_SHARED, RAM_PMEM.
+ * @ram_flags: RamBlock flags. Supported flags: RAM_SHARED, RAM_PMEM,
+ * RAM_NORESERVE,
* @path: the path in which to allocate the RAM.
* @readonly: true to open @path for reading, false for read/write.
* @errp: pointer to Error*, to store an error if it happens.
@@ -1031,7 +1039,8 @@ void memory_region_init_ram_from_file(MemoryRegion *mr,
* @owner: the object that tracks the region's reference count
* @name: the name of the region.
* @size: size of the region.
- * @ram_flags: RamBlock flags. Supported flags: RAM_SHARED, RAM_PMEM.
+ * @ram_flags: RamBlock flags. Supported flags: RAM_SHARED, RAM_PMEM,
+ * RAM_NORESERVE.
* @fd: the fd to mmap.
* @offset: offset within the file referenced by fd
* @errp: pointer to Error*, to store an error if it happens.
diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
index 6d4513f8e2..551876bed0 100644
--- a/include/exec/ram_addr.h
+++ b/include/exec/ram_addr.h
@@ -104,7 +104,8 @@ long qemu_maxrampagesize(void);
* Parameters:
* @size: the size in bytes of the ram block
* @mr: the memory region where the ram block is
- * @ram_flags: RamBlock flags. Supported flags: RAM_SHARED, RAM_PMEM.
+ * @ram_flags: RamBlock flags. Supported flags: RAM_SHARED, RAM_PMEM,
+ * RAM_NORESERVE.
* @mem_path or @fd: specify the backing file or device
* @readonly: true to open @path for reading, false for read/write.
* @errp: pointer to Error*, to store an error if it happens
diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index 88106e88fc..38a3327db9 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -362,7 +362,8 @@ extern "C" {
int qemu_daemon(int nochdir, int noclose);
void *qemu_try_memalign(size_t alignment, size_t size);
void *qemu_memalign(size_t alignment, size_t size);
-void *qemu_anon_ram_alloc(size_t size, uint64_t *align, bool shared);
+void *qemu_anon_ram_alloc(size_t size, uint64_t *align, bool shared,
+ bool noreserve);
void qemu_vfree(void *ptr);
void qemu_anon_ram_free(void *ptr, size_t size);
@@ -383,6 +384,12 @@ void qemu_anon_ram_free(void *ptr, size_t size);
*/
#define QEMU_MAP_SYNC (1 << 2)
+/*
+ * Use MAP_NORESERVE to skip reservation of swap space (or huge pages if
+ * applicable). Bail out if not supported/effective.
+ */
+#define QEMU_MAP_NORESERVE (1 << 3)
+
#define QEMU_MADV_INVALID -1
diff --git a/migration/ram.c b/migration/ram.c
index 60ea913c54..723af67c2e 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -3343,8 +3343,7 @@ int colo_init_ram_cache(void)
WITH_RCU_READ_LOCK_GUARD() {
RAMBLOCK_FOREACH_NOT_IGNORED(block) {
block->colo_cache = qemu_anon_ram_alloc(block->used_length,
- NULL,
- false);
+ NULL, false, false);
if (!block->colo_cache) {
error_report("%s: Can't alloc memory for COLO cache of block %s,"
"size 0x" RAM_ADDR_FMT, __func__, block->idstr,
diff --git a/softmmu/physmem.c b/softmmu/physmem.c
index 24228c838c..a7725d8474 100644
--- a/softmmu/physmem.c
+++ b/softmmu/physmem.c
@@ -1591,6 +1591,7 @@ static void *file_ram_alloc(RAMBlock *block,
qemu_map_flags = readonly ? QEMU_MAP_READONLY : 0;
qemu_map_flags |= (block->flags & RAM_SHARED) ? QEMU_MAP_SHARED : 0;
qemu_map_flags |= (block->flags & RAM_PMEM) ? QEMU_MAP_SYNC : 0;
+ qemu_map_flags |= (block->flags & RAM_NORESERVE) ? QEMU_MAP_NORESERVE : 0;
area = qemu_ram_mmap(fd, memory, block->mr->align, qemu_map_flags, offset);
if (area == MAP_FAILED) {
error_setg_errno(errp, errno,
@@ -1716,6 +1717,11 @@ bool qemu_ram_is_shared(RAMBlock *rb)
return rb->flags & RAM_SHARED;
}
+bool qemu_ram_is_noreserve(RAMBlock *rb)
+{
+ return rb->flags & RAM_NORESERVE;
+}
+
/* Note: Only set at the start of postcopy */
bool qemu_ram_is_uf_zeroable(RAMBlock *rb)
{
@@ -1950,6 +1956,7 @@ static void dirty_memory_extend(ram_addr_t old_ram_size,
static void ram_block_add(RAMBlock *new_block, Error **errp)
{
+ const bool noreserve = qemu_ram_is_noreserve(new_block);
const bool shared = qemu_ram_is_shared(new_block);
RAMBlock *block;
RAMBlock *last_block = NULL;
@@ -1973,7 +1980,7 @@ static void ram_block_add(RAMBlock *new_block, Error **errp)
} else {
new_block->host = qemu_anon_ram_alloc(new_block->max_length,
&new_block->mr->align,
- shared);
+ shared, noreserve);
if (!new_block->host) {
error_setg_errno(errp, errno,
"cannot set up guest memory '%s'",
@@ -2045,7 +2052,7 @@ RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr,
int64_t file_size, file_align;
/* Just support these ram flags by now. */
- assert((ram_flags & ~(RAM_SHARED | RAM_PMEM)) == 0);
+ assert((ram_flags & ~(RAM_SHARED | RAM_PMEM | RAM_NORESERVE)) == 0);
if (xen_enabled()) {
error_setg(errp, "-mem-path not supported with Xen");
@@ -2137,6 +2144,8 @@ RAMBlock *qemu_ram_alloc_internal(ram_addr_t size, ram_addr_t max_size,
Error *local_err = NULL;
assert((ram_flags & ~(RAM_SHARED | RAM_RESIZEABLE | RAM_PREALLOC)) == 0);
+ assert((ram_flags & ~(RAM_SHARED | RAM_RESIZEABLE | RAM_PREALLOC |
+ RAM_NORESERVE)) == 0);
assert(!host ^ (ram_flags & RAM_PREALLOC));
size = HOST_PAGE_ALIGN(size);
@@ -2170,7 +2179,7 @@ RAMBlock *qemu_ram_alloc_from_ptr(ram_addr_t size, void *host,
RAMBlock *qemu_ram_alloc(ram_addr_t size, uint32_t ram_flags,
MemoryRegion *mr, Error **errp)
{
- assert((ram_flags & ~RAM_SHARED) == 0);
+ assert((ram_flags & ~(RAM_SHARED | RAM_NORESERVE)) == 0);
return qemu_ram_alloc_internal(size, size, NULL, NULL, ram_flags, mr, errp);
}
diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c
index 1ddc0e2a1e..d0cf4aaee5 100644
--- a/util/mmap-alloc.c
+++ b/util/mmap-alloc.c
@@ -20,6 +20,7 @@
#include "qemu/osdep.h"
#include "qemu/mmap-alloc.h"
#include "qemu/host-utils.h"
+#include "qemu/error-report.h"
#define HUGETLBFS_MAGIC 0x958458f6
@@ -121,6 +122,7 @@ static void *mmap_reserve(size_t size, int fd)
static void *mmap_activate(void *ptr, size_t size, int fd,
uint32_t qemu_map_flags, off_t map_offset)
{
+ const bool noreserve = qemu_map_flags & QEMU_MAP_NORESERVE;
const bool readonly = qemu_map_flags & QEMU_MAP_READONLY;
const bool shared = qemu_map_flags & QEMU_MAP_SHARED;
const bool sync = qemu_map_flags & QEMU_MAP_SYNC;
@@ -129,6 +131,11 @@ static void *mmap_activate(void *ptr, size_t size, int fd,
int flags = MAP_FIXED;
void *activated_ptr;
+ if (noreserve) {
+ error_report("Skipping reservation of swap space is not supported");
+ return MAP_FAILED;
+ }
+
flags |= fd == -1 ? MAP_ANONYMOUS : 0;
flags |= shared ? MAP_SHARED : MAP_PRIVATE;
if (shared && sync) {
diff --git a/util/oslib-posix.c b/util/oslib-posix.c
index 0dd7784a88..e8bdb02e1d 100644
--- a/util/oslib-posix.c
+++ b/util/oslib-posix.c
@@ -227,9 +227,11 @@ void *qemu_memalign(size_t alignment, size_t size)
}
/* alloc shared memory pages */
-void *qemu_anon_ram_alloc(size_t size, uint64_t *alignment, bool shared)
+void *qemu_anon_ram_alloc(size_t size, uint64_t *alignment, bool shared,
+ bool noreserve)
{
- const uint32_t qemu_map_flags = shared ? QEMU_MAP_SHARED : 0;
+ const uint32_t qemu_map_flags = (shared ? QEMU_MAP_SHARED : 0) |
+ (noreserve ? QEMU_MAP_NORESERVE : 0);
size_t align = QEMU_VMALLOC_ALIGN;
void *ptr = qemu_ram_mmap(-1, size, align, qemu_map_flags, 0);
diff --git a/util/oslib-win32.c b/util/oslib-win32.c
index ca99356fdf..ee3a3692d8 100644
--- a/util/oslib-win32.c
+++ b/util/oslib-win32.c
@@ -38,6 +38,7 @@
#include "trace.h"
#include "qemu/sockets.h"
#include "qemu/cutils.h"
+#include "qemu/error-report.h"
#include <malloc.h>
/* this must come after including "trace.h" */
@@ -76,10 +77,20 @@ static int get_allocation_granularity(void)
return system_info.dwAllocationGranularity;
}
-void *qemu_anon_ram_alloc(size_t size, uint64_t *align, bool shared)
+void *qemu_anon_ram_alloc(size_t size, uint64_t *align, bool shared,
+ bool noreserve)
{
void *ptr;
+ if (noreserve) {
+ /*
+ * We need a MEM_COMMIT before accessing any memory in a MEM_RESERVE
+ * area; we cannot easily mimic POSIX MAP_NORESERVE semantics.
+ */
+ error_report("Skipping reservation of swap space is not supported.");
+ return NULL;
+ }
+
ptr = VirtualAlloc(NULL, size, MEM_COMMIT, PAGE_READWRITE);
trace_qemu_anon_ram_alloc(size, ptr);
--
2.31.1
next prev parent reply other threads:[~2021-06-15 14:14 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-15 13:38 [PULL 00/33] Misc patches for 2021-06-15 Paolo Bonzini
2021-06-15 13:38 ` [PULL 01/33] vnc: avoid deprecation warnings for SASL on OS X Paolo Bonzini
2021-06-15 13:38 ` [PULL 02/33] vl: Fix an assert failure in error path Paolo Bonzini
2021-06-15 13:38 ` [PULL 03/33] qemu-config: use qemu_opts_from_qdict Paolo Bonzini
2021-06-15 13:38 ` [PULL 04/33] block/scsi: correctly emulate the VPD block limits page Paolo Bonzini
2021-06-15 13:38 ` [PULL 05/33] runstate: Initialize Error * to NULL Paolo Bonzini
2021-06-15 13:38 ` [PULL 06/33] esp: only assert INTR_DC interrupt flag if selection fails Paolo Bonzini
2021-06-15 13:38 ` [PULL 07/33] esp: only set ESP_RSEQ at the start of the select sequence Paolo Bonzini
2021-06-15 13:38 ` [PULL 08/33] esp: allow non-DMA callback in esp_transfer_data() initial transfer Paolo Bonzini
2021-06-15 13:38 ` [PULL 09/33] esp: handle non-DMA transfers from the target one byte at a time Paolo Bonzini
2021-06-15 13:38 ` [PULL 10/33] esp: ensure PDMA write transfers are flushed from the FIFO to the target immediately Paolo Bonzini
2021-06-15 13:38 ` [PULL 11/33] esp: revert 75ef849696 "esp: correctly fill bus id with requested lun" Paolo Bonzini
2021-06-15 13:38 ` [PULL 12/33] esp: correctly accumulate extended messages for PDMA Paolo Bonzini
2021-06-15 13:38 ` [PULL 13/33] esp: fix migration version check in esp_is_version_5() Paolo Bonzini
2021-06-15 13:38 ` [PULL 14/33] esp: store lun coming from the MESSAGE OUT phase Paolo Bonzini
2021-06-15 13:38 ` [PULL 15/33] softmmu/physmem: Mark shared anonymous memory RAM_SHARED Paolo Bonzini
2021-06-15 13:38 ` [PULL 16/33] softmmu/physmem: Fix ram_block_discard_range() to handle shared anonymous memory Paolo Bonzini
2021-06-15 13:38 ` [PULL 17/33] softmmu/physmem: Fix qemu_ram_remap() " Paolo Bonzini
2021-06-15 13:38 ` [PULL 18/33] util/mmap-alloc: Factor out calculation of the pagesize for the guard page Paolo Bonzini
2021-06-15 13:38 ` [PULL 19/33] util/mmap-alloc: Factor out reserving of a memory region to mmap_reserve() Paolo Bonzini
2021-06-15 13:38 ` [PULL 20/33] util/mmap-alloc: Factor out activating of memory to mmap_activate() Paolo Bonzini
2021-06-15 13:38 ` [PULL 21/33] softmmu/memory: Pass ram_flags to qemu_ram_alloc_from_fd() Paolo Bonzini
2021-06-15 13:38 ` [PULL 22/33] softmmu/memory: Pass ram_flags to memory_region_init_ram_shared_nomigrate() Paolo Bonzini
2021-06-15 13:38 ` [PULL 23/33] softmmu/memory: Pass ram_flags to qemu_ram_alloc() and qemu_ram_alloc_internal() Paolo Bonzini
2021-06-15 13:38 ` [PULL 24/33] util/mmap-alloc: Pass flags instead of separate bools to qemu_ram_mmap() Paolo Bonzini
2021-06-15 13:38 ` Paolo Bonzini [this message]
2021-06-15 13:38 ` [PULL 26/33] util/mmap-alloc: Support RAM_NORESERVE via MAP_NORESERVE under Linux Paolo Bonzini
2021-06-15 13:38 ` [PULL 27/33] hostmem: Wire up RAM_NORESERVE via "reserve" property Paolo Bonzini
2021-06-15 13:38 ` [PULL 28/33] qmp: Clarify memory backend properties returned via query-memdev Paolo Bonzini
2021-06-15 13:38 ` [PULL 29/33] qmp: Include "share" property of memory backends Paolo Bonzini
2021-06-15 13:38 ` [PULL 30/33] hmp: Print "share" property of memory backends with "info memdev" Paolo Bonzini
2021-06-15 13:38 ` [PULL 31/33] qmp: Include "reserve" property of memory backends Paolo Bonzini
2021-06-15 13:38 ` [PULL 32/33] hmp: Print "reserve" property of memory backends with "info memdev" Paolo Bonzini
2021-06-15 13:38 ` [PULL 33/33] configure: map x32 to cpu_family x86_64 for meson Paolo Bonzini
2021-06-15 14:17 ` [PULL 00/33] Misc patches for 2021-06-15 Peter Maydell
2021-06-15 16:52 ` Philippe Mathieu-Daudé
2021-06-17 10:06 ` Alex Bennée
2021-06-17 12:55 ` Paolo Bonzini
2021-06-17 15:34 ` Thomas Huth
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