From: Yan Zhao <yan.y.z...@intel.com>
(This is just the POC code to use in-place conversion gmem.)
Try to use in-place conversion gmem when it is supported.
When in-place conversion is enabled, there is no need to discard memory
since it still needs to be used as the memory of opposite attribute
after conversion.
For a upstreamable solution, we can introduce memory-backend-guestmemfd
for in-place conversion. With the non in-place conversion, it needs
seperate non-gmem memory to back the shared memory and gmem is created
implicitly and internally based on vm type. While with in-place
conversion, there is no need for seperate non-gmem memory because gmem
itself can be served as shared memory. So that we can introduce
memory-backend-guestmemfd as the specific backend for in-place
conversion gmem.
Signed-off-by: Yan Zhao <yan.y.z...@intel.com>
Co-developed-by Xiaoyao Li <xiaoyao...@intel.com>
Signed-off-by: Xiaoyao Li <xiaoyao...@intel.com>
---
accel/kvm/kvm-all.c | 79 ++++++++++++++++++++++++++++-----------
accel/stubs/kvm-stub.c | 1 +
include/system/kvm.h | 1 +
include/system/memory.h | 2 +
include/system/ramblock.h | 1 +
system/memory.c | 7 ++++
system/physmem.c | 21 ++++++++++-
7 files changed, 90 insertions(+), 22 deletions(-)
diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index a106d1ba0f0b..609537738d38 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -105,6 +105,7 @@ static int kvm_sstep_flags;
static bool kvm_immediate_exit;
static uint64_t kvm_supported_memory_attributes;
static bool kvm_guest_memfd_supported;
+bool kvm_guest_memfd_inplace_supported;
static hwaddr kvm_max_slot_size = ~0;
static const KVMCapabilityInfo kvm_required_capabilites[] = {
@@ -1487,6 +1488,30 @@ static int kvm_set_memory_attributes(hwaddr start,
uint64_t size, uint64_t attr)
return r;
}
+static int kvm_set_guest_memfd_shareability(MemoryRegion *mr, ram_addr_t
offset,
+ uint64_t size, bool shared)
+{
+ int guest_memfd = mr->ram_block->guest_memfd;
+ struct kvm_gmem_convert param = {
+ .offset = offset,
+ .size = size,
+ .error_offset = 0,
+ };
+ unsigned long op;
+ int r;
+
+ op = shared ? KVM_GMEM_CONVERT_SHARED : KVM_GMEM_CONVERT_PRIVATE;
+
+ r = ioctl(guest_memfd, op, ¶m);
+ if (r) {
+ error_report("failed to set guest_memfd offset 0x%lx size 0x%lx to %s
"
+ "error '%s' error offset 0x%llx",
+ offset, size, shared ? "shared" : "private",
+ strerror(errno), param.error_offset);
+ }
+ return r;
+}
+
int kvm_set_memory_attributes_private(hwaddr start, uint64_t size)
{
return kvm_set_memory_attributes(start, size,
KVM_MEMORY_ATTRIBUTE_PRIVATE);
@@ -1604,7 +1629,8 @@ static void kvm_set_phys_mem(KVMMemoryListener *kml,
abort();
}
- if (memory_region_has_guest_memfd(mr)) {
+ if (memory_region_has_guest_memfd(mr) &&
+ !memory_region_guest_memfd_in_place_conversion(mr)) {
err = kvm_set_memory_attributes_private(start_addr, slot_size);
if (err) {
error_report("%s: failed to set memory attribute private: %s",
@@ -2779,6 +2805,9 @@ static int kvm_init(AccelState *as, MachineState *ms)
kvm_check_extension(s, KVM_CAP_GUEST_MEMFD) &&
kvm_check_extension(s, KVM_CAP_USER_MEMORY2) &&
(kvm_supported_memory_attributes & KVM_MEMORY_ATTRIBUTE_PRIVATE);
+ kvm_guest_memfd_inplace_supported =
+ kvm_check_extension(s, KVM_CAP_GMEM_SHARED_MEM) &&
+ kvm_check_extension(s, KVM_CAP_GMEM_CONVERSION);
kvm_pre_fault_memory_supported = kvm_vm_check_extension(s,
KVM_CAP_PRE_FAULT_MEMORY);
if (s->kernel_irqchip_split == ON_OFF_AUTO_AUTO) {
@@ -3056,6 +3085,7 @@ static void kvm_eat_signals(CPUState *cpu)
int kvm_convert_memory(hwaddr start, hwaddr size, bool to_private)
{
+ bool in_place_conversion = false;
MemoryRegionSection section;
ram_addr_t offset;
MemoryRegion *mr;
@@ -3112,18 +3142,23 @@ int kvm_convert_memory(hwaddr start, hwaddr size, bool
to_private)
goto out_unref;
}
- if (to_private) {
- ret = kvm_set_memory_attributes_private(start, size);
- } else {
- ret = kvm_set_memory_attributes_shared(start, size);
- }
- if (ret) {
- goto out_unref;
- }
-
addr = memory_region_get_ram_ptr(mr) + section.offset_within_region;
rb = qemu_ram_block_from_host(addr, false, &offset);
+ in_place_conversion = memory_region_guest_memfd_in_place_conversion(mr);
+ if (in_place_conversion) {
+ ret = kvm_set_guest_memfd_shareability(mr, offset, size, !to_private);
+ } else {
+ if (to_private) {
+ ret = kvm_set_memory_attributes_private(start, size);
+ } else {
+ ret = kvm_set_memory_attributes_shared(start, size);
+ }
+ }
+ if (ret) {
+ goto out_unref;
+ }
+
ret = ram_block_attributes_state_change(RAM_BLOCK_ATTRIBUTES(mr->rdm),
offset, size, to_private);
if (ret) {
@@ -3133,17 +3168,19 @@ int kvm_convert_memory(hwaddr start, hwaddr size, bool
to_private)
goto out_unref;
}
- if (to_private) {
- if (rb->page_size != qemu_real_host_page_size()) {
- /*
- * shared memory is backed by hugetlb, which is supposed to be
- * pre-allocated and doesn't need to be discarded
- */
- goto out_unref;
- }
- ret = ram_block_discard_range(rb, offset, size);
- } else {
- ret = ram_block_discard_guest_memfd_range(rb, offset, size);
+ if (!in_place_conversion) {
+ if (to_private) {
+ if (rb->page_size != qemu_real_host_page_size()) {
+ /*
+ * shared memory is backed by hugetlb, which is supposed to be
+ * pre-allocated and doesn't need to be discarded
+ */
+ goto out_unref;
+ }
+ ret = ram_block_discard_range(rb, offset, size);
+ } else {
+ ret = ram_block_discard_guest_memfd_range(rb, offset, size);
+ }
}
out_unref:
diff --git a/accel/stubs/kvm-stub.c b/accel/stubs/kvm-stub.c
index 68cd33ba9735..bf0ccae27b62 100644
--- a/accel/stubs/kvm-stub.c
+++ b/accel/stubs/kvm-stub.c
@@ -24,6 +24,7 @@ bool kvm_gsi_direct_mapping;
bool kvm_allowed;
bool kvm_readonly_mem_allowed;
bool kvm_msi_use_devid;
+bool kvm_guest_memfd_inplace_supported;
void kvm_flush_coalesced_mmio_buffer(void)
{
diff --git a/include/system/kvm.h b/include/system/kvm.h
index 3c7d31473663..32f2be5f92e1 100644
--- a/include/system/kvm.h
+++ b/include/system/kvm.h
@@ -43,6 +43,7 @@ extern bool kvm_gsi_direct_mapping;
extern bool kvm_readonly_mem_allowed;
extern bool kvm_msi_use_devid;
extern bool kvm_pre_fault_memory_supported;
+extern bool kvm_guest_memfd_inplace_supported;
#define kvm_enabled() (kvm_allowed)
/**
diff --git a/include/system/memory.h b/include/system/memory.h
index 46248d4a52c4..f14fbf65805d 100644
--- a/include/system/memory.h
+++ b/include/system/memory.h
@@ -1812,6 +1812,8 @@ bool memory_region_is_protected(MemoryRegion *mr);
*/
bool memory_region_has_guest_memfd(MemoryRegion *mr);
+bool memory_region_guest_memfd_in_place_conversion(MemoryRegion *mr);
+
/**
* memory_region_get_iommu: check whether a memory region is an iommu
*
diff --git a/include/system/ramblock.h b/include/system/ramblock.h
index 87e847e184aa..87757940ea21 100644
--- a/include/system/ramblock.h
+++ b/include/system/ramblock.h
@@ -46,6 +46,7 @@ struct RAMBlock {
int fd;
uint64_t fd_offset;
int guest_memfd;
+ uint64_t guest_memfd_flags;
RamBlockAttributes *attributes;
size_t page_size;
/* dirty bitmap used during migration */
diff --git a/system/memory.c b/system/memory.c
index e8d9b15b28f6..6870a41629ef 100644
--- a/system/memory.c
+++ b/system/memory.c
@@ -35,6 +35,7 @@
#include "memory-internal.h"
+#include <linux/kvm.h>
//#define DEBUG_UNASSIGNED
static unsigned memory_region_transaction_depth;
@@ -1878,6 +1879,12 @@ bool memory_region_has_guest_memfd(MemoryRegion *mr)
return mr->ram_block && mr->ram_block->guest_memfd >= 0;
}
+bool memory_region_guest_memfd_in_place_conversion(MemoryRegion *mr)
+{
+ return mr && memory_region_has_guest_memfd(mr) &&
+ (mr->ram_block->guest_memfd_flags &
GUEST_MEMFD_FLAG_SUPPORT_SHARED);
+}
+
uint8_t memory_region_get_dirty_log_mask(MemoryRegion *mr)
{
uint8_t mask = mr->dirty_log_mask;
diff --git a/system/physmem.c b/system/physmem.c
index 130c148ffb5c..955480685310 100644
--- a/system/physmem.c
+++ b/system/physmem.c
@@ -89,6 +89,9 @@
#include "memory-internal.h"
+#include <linux/guestmem.h>
+#include <linux/kvm.h>
+
//#define DEBUG_SUBPAGE
/* ram_list is read under rcu_read_lock()/rcu_read_unlock(). Writes
@@ -1913,6 +1916,9 @@ static void ram_block_add(RAMBlock *new_block, Error
**errp)
if (new_block->flags & RAM_GUEST_MEMFD) {
int ret;
+ bool in_place = kvm_guest_memfd_inplace_supported;
+
+ new_block->guest_memfd_flags = 0;
if (!kvm_enabled()) {
error_setg(errp, "cannot set up private guest memory for %s: KVM
required",
@@ -1929,13 +1935,26 @@ static void ram_block_add(RAMBlock *new_block, Error
**errp)
goto out_free;
}
+ if (in_place) {
+ new_block->guest_memfd_flags |= GUEST_MEMFD_FLAG_SUPPORT_SHARED |
+ GUEST_MEMFD_FLAG_INIT_PRIVATE;
+ }
+
new_block->guest_memfd = kvm_create_guest_memfd(new_block->max_length,
- 0, errp);
+ new_block->guest_memfd_flags, errp);
if (new_block->guest_memfd < 0) {
qemu_mutex_unlock_ramlist();
goto out_free;
}
+ if (in_place) {
+ qemu_ram_munmap(new_block->fd, new_block->host,
new_block->max_length);
+ new_block->host = qemu_ram_mmap(new_block->guest_memfd,
+ new_block->max_length,
+ QEMU_VMALLOC_ALIGN,
+ QEMU_MAP_SHARED, 0);
+ }
+
/*
* The attribute bitmap of the RamBlockAttributes is default to
* discarded, which mimics the behavior of kvm_set_phys_mem() when it
--
2.43.0
