[RFC PATCH v2 02/21] RAMBlock: Add support of KVM private gmem

[Xiaoyao Li <xiaoyao.li@intel.com>]

From: Chao Peng <chao.p.peng@linux.intel.com>

Add KVM gmem support to RAMBlock so both normal hva based memory
and kvm gmem fd based private memory can be associated in one RAMBlock.

Introduce new flag RAM_KVM_GMEM. It calls KVM ioctl to create private
gmem for the RAMBlock when it's set.

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
---
 accel/kvm/kvm-all.c     | 17 +++++++++++++++++
 include/exec/memory.h   |  3 +++
 include/exec/ramblock.h |  1 +
 include/sysemu/kvm.h    |  2 ++
 softmmu/physmem.c       | 18 +++++++++++++++---
 5 files changed, 38 insertions(+), 3 deletions(-)

diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index 60aacd925393..185ae16d9620 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -4225,3 +4225,20 @@ void query_stats_schemas_cb(StatsSchemaList **result, Error **errp)
         query_stats_schema_vcpu(first_cpu, &stats_args);
     }
 }
+
+int kvm_create_guest_memfd(uint64_t size, uint64_t flags, Error **errp)
+{
+    int fd;
+    struct kvm_create_guest_memfd gmem = {
+        .size = size,
+        /* TODO: to decide whether KVM_GUEST_MEMFD_ALLOW_HUGEPAGE is supported */
+        .flags = flags,
+    };
+
+    fd = kvm_vm_ioctl(kvm_state, KVM_CREATE_GUEST_MEMFD, &gmem);
+    if (fd < 0) {
+        error_setg_errno(errp, errno, "%s: error creating kvm gmem\n", __func__);
+    }
+
+    return fd;
+}
diff --git a/include/exec/memory.h b/include/exec/memory.h
index 68284428f87c..227cb2578e95 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -235,6 +235,9 @@ typedef struct IOMMUTLBEvent {
 /* RAM is an mmap-ed named file */
 #define RAM_NAMED_FILE (1 << 9)
 
+/* RAM can be private that has kvm gmem backend */
+#define RAM_KVM_GMEM    (1 << 10)
+
 static inline void iommu_notifier_init(IOMMUNotifier *n, IOMMUNotify fn,
                                        IOMMUNotifierFlag flags,
                                        hwaddr start, hwaddr end,
diff --git a/include/exec/ramblock.h b/include/exec/ramblock.h
index 69c6a5390293..0d158b3909c9 100644
--- a/include/exec/ramblock.h
+++ b/include/exec/ramblock.h
@@ -41,6 +41,7 @@ struct RAMBlock {
     QLIST_HEAD(, RAMBlockNotifier) ramblock_notifiers;
     int fd;
     uint64_t fd_offset;
+    int gmem_fd;
     size_t page_size;
     /* dirty bitmap used during migration */
     unsigned long *bmap;
diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
index 115f0cca79d1..f5b74c8dd8c5 100644
--- a/include/sysemu/kvm.h
+++ b/include/sysemu/kvm.h
@@ -580,4 +580,6 @@ bool kvm_arch_cpu_check_are_resettable(void);
 bool kvm_dirty_ring_enabled(void);
 
 uint32_t kvm_dirty_ring_size(void);
+
+int kvm_create_guest_memfd(uint64_t size, uint64_t flags, Error **errp);
 #endif
diff --git a/softmmu/physmem.c b/softmmu/physmem.c
index 3df73542e1fe..2d98a88f41f0 100644
--- a/softmmu/physmem.c
+++ b/softmmu/physmem.c
@@ -1824,6 +1824,16 @@ static void ram_block_add(RAMBlock *new_block, Error **errp)
         }
     }
 
+    if (kvm_enabled() && new_block->flags & RAM_KVM_GMEM &&
+        new_block->gmem_fd < 0) {
+        new_block->gmem_fd = kvm_create_guest_memfd(new_block->max_length,
+                                                    0, errp);
+        if (new_block->gmem_fd < 0) {
+            qemu_mutex_unlock_ramlist();
+            return;
+        }
+    }
+
     new_ram_size = MAX(old_ram_size,
               (new_block->offset + new_block->max_length) >> TARGET_PAGE_BITS);
     if (new_ram_size > old_ram_size) {
@@ -1885,7 +1895,7 @@ RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr,
 
     /* Just support these ram flags by now. */
     assert((ram_flags & ~(RAM_SHARED | RAM_PMEM | RAM_NORESERVE |
-                          RAM_PROTECTED | RAM_NAMED_FILE)) == 0);
+                          RAM_PROTECTED | RAM_NAMED_FILE | RAM_KVM_GMEM)) == 0);
 
     if (xen_enabled()) {
         error_setg(errp, "-mem-path not supported with Xen");
@@ -1920,6 +1930,7 @@ RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr,
     new_block->used_length = size;
     new_block->max_length = size;
     new_block->flags = ram_flags;
+    new_block->gmem_fd = -1;
     new_block->host = file_ram_alloc(new_block, size, fd, readonly,
                                      !file_size, offset, errp);
     if (!new_block->host) {
@@ -1978,7 +1989,7 @@ 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 |
-                          RAM_NORESERVE)) == 0);
+                          RAM_NORESERVE| RAM_KVM_GMEM)) == 0);
     assert(!host ^ (ram_flags & RAM_PREALLOC));
 
     size = HOST_PAGE_ALIGN(size);
@@ -1990,6 +2001,7 @@ RAMBlock *qemu_ram_alloc_internal(ram_addr_t size, ram_addr_t max_size,
     new_block->max_length = max_size;
     assert(max_size >= size);
     new_block->fd = -1;
+    new_block->gmem_fd = -1;
     new_block->page_size = qemu_real_host_page_size();
     new_block->host = host;
     new_block->flags = ram_flags;
@@ -2012,7 +2024,7 @@ 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 | RAM_NORESERVE)) == 0);
+    assert((ram_flags & ~(RAM_SHARED | RAM_NORESERVE | RAM_KVM_GMEM)) == 0);
     return qemu_ram_alloc_internal(size, size, NULL, NULL, ram_flags, mr, errp);
 }
 
-- 
2.34.1