[RFC PATCH v2 17/21] kvm: handle KVM_EXIT_MEMORY_FAULT

[Xiaoyao Li <xiaoyao.li@xxxxxxxxx>]

From: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>

Currently only KVM_MEMORY_EXIT_FLAG_PRIVATE in flags is valid when
KVM_EXIT_MEMORY_FAULT happens. It indicates userspace needs to do
the memory conversion on the RAMBlock to turn the memory into desired
attribute, i.e., private/shared.

Note, KVM_EXIT_MEMORY_FAULT makes sense only when the RAMBlock has
gmem memory backend.

Signed-off-by: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>
Signed-off-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
---
 accel/kvm/kvm-all.c | 54 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index 7e32ee83b258..c67aa66b0559 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -3040,6 +3040,50 @@ static void kvm_eat_signals(CPUState *cpu)
     } while (sigismember(&chkset, SIG_IPI));
 }
 
+static int kvm_convert_memory(hwaddr start, hwaddr size, bool to_private)
+{
+    MemoryRegionSection section;
+    ram_addr_t offset;
+    RAMBlock *rb;
+    void *addr;
+    int ret = -1;
+
+    section = memory_region_find(get_system_memory(), start, size);
+    if (!section.mr) {
+        return ret;
+    }
+
+    if (memory_region_has_gmem_fd(section.mr)) {
+        if (to_private) {
+            ret = kvm_set_memory_attributes_private(start, size);
+        } else {
+            ret = kvm_set_memory_attributes_shared(start, size);
+        }
+
+        if (ret) {
+            memory_region_unref(section.mr);
+            return ret;
+        }
+
+        addr = memory_region_get_ram_ptr(section.mr) +
+               section.offset_within_region;
+        rb = qemu_ram_block_from_host(addr, false, &offset);
+        /*
+         * With KVM_SET_MEMORY_ATTRIBUTES by kvm_set_memory_attributes(),
+         * operation on underlying file descriptor is only for releasing
+         * unnecessary pages.
+         */
+        ram_block_convert_range(rb, offset, size, to_private);
+    } else {
+        warn_report("Convert non guest-memfd backed memory region "
+                    "(0x%"HWADDR_PRIx" ,+ 0x%"HWADDR_PRIx") to %s",
+                    start, size, to_private ? "private" : "shared");
+    }
+
+    memory_region_unref(section.mr);
+    return ret;
+}
+
 int kvm_cpu_exec(CPUState *cpu)
 {
     struct kvm_run *run = cpu->kvm_run;
@@ -3198,6 +3242,16 @@ int kvm_cpu_exec(CPUState *cpu)
                 break;
             }
             break;
+        case KVM_EXIT_MEMORY_FAULT:
+            if (run->memory.flags & ~KVM_MEMORY_EXIT_FLAG_PRIVATE) {
+                error_report("KVM_EXIT_MEMORY_FAULT: Unknown flag 0x%" PRIx64,
+                             (uint64_t)run->memory.flags);
+                ret = -1;
+                break;
+            }
+            ret = kvm_convert_memory(run->memory.gpa, run->memory.size,
+                                     run->memory.flags & KVM_MEMORY_EXIT_FLAG_PRIVATE);
+            break;
         default:
             DPRINTF("kvm_arch_handle_exit\n");
             ret = kvm_arch_handle_exit(cpu, run);
-- 
2.34.1