diff mbox series

[RFC,05/19] kvm: Enable KVM_SET_USER_MEMORY_REGION2 for memslot

Message ID 20230731162201.271114-6-xiaoyao.li@intel.com
State New
Headers show
Series QEMU gmem implemention | expand

Commit Message

Xiaoyao Li July 31, 2023, 4:21 p.m. UTC 
From: Chao Peng <chao.p.peng@linux.intel.com>

Switch to KVM_SET_USER_MEMORY_REGION2 when supported by KVM.

With KVM_SET_USER_MEMORY_REGION2, QEMU can set up memory region that
backen'ed both by hva-based shared memory and gmem fd based private
memory.

Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
Codeveloped-by: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
---
 accel/kvm/kvm-all.c      | 57 +++++++++++++++++++++++++++++++++-------
 accel/kvm/trace-events   |  2 +-
 include/sysemu/kvm_int.h |  2 ++
 3 files changed, 51 insertions(+), 10 deletions(-)

Comments

Claudio Fontana Aug. 1, 2023, 5:10 p.m. UTC | #1 
On 7/31/23 18:21, Xiaoyao Li wrote:
> From: Chao Peng <chao.p.peng@linux.intel.com>
> 
> Switch to KVM_SET_USER_MEMORY_REGION2 when supported by KVM.
> 
> With KVM_SET_USER_MEMORY_REGION2, QEMU can set up memory region that
> backen'ed both by hva-based shared memory and gmem fd based private
> memory.
> 
> Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
> Codeveloped-by: Xiaoyao Li <xiaoyao.li@intel.com>
> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> ---
>  accel/kvm/kvm-all.c      | 57 +++++++++++++++++++++++++++++++++-------
>  accel/kvm/trace-events   |  2 +-
>  include/sysemu/kvm_int.h |  2 ++
>  3 files changed, 51 insertions(+), 10 deletions(-)
> 
> diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
> index d8eee405de24..7b1818334ba7 100644
> --- a/accel/kvm/kvm-all.c
> +++ b/accel/kvm/kvm-all.c
> @@ -288,35 +288,68 @@ int kvm_physical_memory_addr_from_host(KVMState *s, void *ram,
>  static int kvm_set_user_memory_region(KVMMemoryListener *kml, KVMSlot *slot, bool new)
>  {
>      KVMState *s = kvm_state;
> -    struct kvm_userspace_memory_region mem;
> +    struct kvm_userspace_memory_region2 mem;
> +    static int cap_user_memory2 = -1;
>      int ret;
>  
> +    if (cap_user_memory2 == -1) {
> +        cap_user_memory2 = kvm_check_extension(s, KVM_CAP_USER_MEMORY2);
> +    }
> +
> +    if (!cap_user_memory2 && slot->fd >= 0) {
> +        error_report("%s, KVM doesn't support gmem!", __func__);
> +        exit(1);
> +    }

We handle this special error case here,
while the existing callers of kvm_set_user_memory_region handle the other error cases in different places.

Not that the rest of kvm-all does an excellent job at error handling, but maybe we can avoid compounding on the issue.

> +
>      mem.slot = slot->slot | (kml->as_id << 16);
>      mem.guest_phys_addr = slot->start_addr;
>      mem.userspace_addr = (unsigned long)slot->ram;
>      mem.flags = slot->flags;
> +    mem.gmem_fd = slot->fd;
> +    mem.gmem_offset = slot->ofs;
>  
> -    if (slot->memory_size && !new && (mem.flags ^ slot->old_flags) & KVM_MEM_READONLY) {
> +    if (slot->memory_size && !new && (slot->flags ^ slot->old_flags) & KVM_MEM_READONLY) {

Why the change if mem.flags == slot->flags ?

>          /* Set the slot size to 0 before setting the slot to the desired
>           * value. This is needed based on KVM commit 75d61fbc. */
>          mem.memory_size = 0;
> -        ret = kvm_vm_ioctl(s, KVM_SET_USER_MEMORY_REGION, &mem);
> +
> +        if (cap_user_memory2) {
> +            ret = kvm_vm_ioctl(s, KVM_SET_USER_MEMORY_REGION2, &mem);
> +        } else {
> +            ret = kvm_vm_ioctl(s, KVM_SET_USER_MEMORY_REGION, &mem);
> +	    }
>          if (ret < 0) {
>              goto err;
>          }
>      }
>      mem.memory_size = slot->memory_size;
> -    ret = kvm_vm_ioctl(s, KVM_SET_USER_MEMORY_REGION, &mem);
> +    if (cap_user_memory2) {
> +        ret = kvm_vm_ioctl(s, KVM_SET_USER_MEMORY_REGION2, &mem);
> +    } else {
> +        ret = kvm_vm_ioctl(s, KVM_SET_USER_MEMORY_REGION, &mem);
> +    }
>      slot->old_flags = mem.flags;
>  err:
>      trace_kvm_set_user_memory(mem.slot >> 16, (uint16_t)mem.slot, mem.flags,
>                                mem.guest_phys_addr, mem.memory_size,
> -                              mem.userspace_addr, ret);
> +                              mem.userspace_addr, mem.gmem_fd,
> +			      mem.gmem_offset, ret);
>      if (ret < 0) {
> -        error_report("%s: KVM_SET_USER_MEMORY_REGION failed, slot=%d,"
> -                     " start=0x%" PRIx64 ", size=0x%" PRIx64 ": %s",
> -                     __func__, mem.slot, slot->start_addr,
> -                     (uint64_t)mem.memory_size, strerror(errno));
> +        if (cap_user_memory2) {
> +                error_report("%s: KVM_SET_USER_MEMORY_REGION2 failed, slot=%d,"
> +                        " start=0x%" PRIx64 ", size=0x%" PRIx64 ","
> +                        " flags=0x%" PRIx32 ","
> +                        " gmem_fd=%" PRId32 ", gmem_offset=0x%" PRIx64 ": %s",
> +                        __func__, mem.slot, slot->start_addr,
> +                (uint64_t)mem.memory_size, mem.flags,
> +                        mem.gmem_fd, (uint64_t)mem.gmem_offset,
> +                        strerror(errno));
> +        } else {
> +                error_report("%s: KVM_SET_USER_MEMORY_REGION failed, slot=%d,"
> +                            " start=0x%" PRIx64 ", size=0x%" PRIx64 ": %s",
> +                __func__, mem.slot, slot->start_addr,
> +                (uint64_t)mem.memory_size, strerror(errno));
> +        }
>      }
>      return ret;
>  }
> @@ -472,6 +505,9 @@ static int kvm_mem_flags(MemoryRegion *mr)
>      if (readonly && kvm_readonly_mem_allowed) {
>          flags |= KVM_MEM_READONLY;
>      }
> +    if (memory_region_can_be_private(mr)) {
> +        flags |= KVM_MEM_PRIVATE;
> +    }
>      return flags;
>  }
>  
> @@ -1402,6 +1438,9 @@ static void kvm_set_phys_mem(KVMMemoryListener *kml,
>          mem->ram_start_offset = ram_start_offset;
>          mem->ram = ram;
>          mem->flags = kvm_mem_flags(mr);
> +        mem->fd = mr->ram_block->gmem_fd;
> +        mem->ofs = (uint8_t*)ram - mr->ram_block->host;
> +
>          kvm_slot_init_dirty_bitmap(mem);
>          err = kvm_set_user_memory_region(kml, mem, true);
>          if (err) {
> diff --git a/accel/kvm/trace-events b/accel/kvm/trace-events
> index 14ebfa1b991c..80694683acea 100644
> --- a/accel/kvm/trace-events
> +++ b/accel/kvm/trace-events
> @@ -15,7 +15,7 @@ kvm_irqchip_update_msi_route(int virq) "Updating MSI route virq=%d"
>  kvm_irqchip_release_virq(int virq) "virq %d"
>  kvm_set_ioeventfd_mmio(int fd, uint64_t addr, uint32_t val, bool assign, uint32_t size, bool datamatch) "fd: %d @0x%" PRIx64 " val=0x%x assign: %d size: %d match: %d"
>  kvm_set_ioeventfd_pio(int fd, uint16_t addr, uint32_t val, bool assign, uint32_t size, bool datamatch) "fd: %d @0x%x val=0x%x assign: %d size: %d match: %d"
> -kvm_set_user_memory(uint16_t as, uint16_t slot, uint32_t flags, uint64_t guest_phys_addr, uint64_t memory_size, uint64_t userspace_addr, int ret) "AddrSpace#%d Slot#%d flags=0x%x gpa=0x%"PRIx64 " size=0x%"PRIx64 " ua=0x%"PRIx64 " ret=%d"
> +kvm_set_user_memory(uint16_t as, uint16_t slot, uint32_t flags, uint64_t guest_phys_addr, uint64_t memory_size, uint64_t userspace_addr, uint32_t fd, uint64_t fd_offset, int ret) "AddrSpace#%d Slot#%d flags=0x%x gpa=0x%"PRIx64 " size=0x%"PRIx64 " ua=0x%"PRIx64 " gmem_fd=%d" " gmem_fd_offset=0x%" PRIx64 " ret=%d"
>  kvm_clear_dirty_log(uint32_t slot, uint64_t start, uint32_t size) "slot#%"PRId32" start 0x%"PRIx64" size 0x%"PRIx32
>  kvm_resample_fd_notify(int gsi) "gsi %d"
>  kvm_dirty_ring_full(int id) "vcpu %d"
> diff --git a/include/sysemu/kvm_int.h b/include/sysemu/kvm_int.h
> index 511b42bde5c4..48220c0793ac 100644
> --- a/include/sysemu/kvm_int.h
> +++ b/include/sysemu/kvm_int.h
> @@ -30,6 +30,8 @@ typedef struct KVMSlot
>      int as_id;
>      /* Cache of the offset in ram address space */
>      ram_addr_t ram_start_offset;
> +    int fd;
> +    hwaddr ofs;
>  } KVMSlot;
>  
>  typedef struct KVMMemoryUpdate {
Xiaoyao Li Aug. 3, 2023, 8:43 a.m. UTC | #2 
On 8/2/2023 1:10 AM, Claudio Fontana wrote:
> On 7/31/23 18:21, Xiaoyao Li wrote:
>> From: Chao Peng <chao.p.peng@linux.intel.com>
>>
>> Switch to KVM_SET_USER_MEMORY_REGION2 when supported by KVM.
>>
>> With KVM_SET_USER_MEMORY_REGION2, QEMU can set up memory region that
>> backen'ed both by hva-based shared memory and gmem fd based private
>> memory.
>>
>> Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
>> Codeveloped-by: Xiaoyao Li <xiaoyao.li@intel.com>
>> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
>> ---
>>   accel/kvm/kvm-all.c      | 57 +++++++++++++++++++++++++++++++++-------
>>   accel/kvm/trace-events   |  2 +-
>>   include/sysemu/kvm_int.h |  2 ++
>>   3 files changed, 51 insertions(+), 10 deletions(-)
>>
>> diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
>> index d8eee405de24..7b1818334ba7 100644
>> --- a/accel/kvm/kvm-all.c
>> +++ b/accel/kvm/kvm-all.c
>> @@ -288,35 +288,68 @@ int kvm_physical_memory_addr_from_host(KVMState *s, void *ram,
>>   static int kvm_set_user_memory_region(KVMMemoryListener *kml, KVMSlot *slot, bool new)
>>   {
>>       KVMState *s = kvm_state;
>> -    struct kvm_userspace_memory_region mem;
>> +    struct kvm_userspace_memory_region2 mem;
>> +    static int cap_user_memory2 = -1;
>>       int ret;
>>   
>> +    if (cap_user_memory2 == -1) {
>> +        cap_user_memory2 = kvm_check_extension(s, KVM_CAP_USER_MEMORY2);
>> +    }
>> +
>> +    if (!cap_user_memory2 && slot->fd >= 0) {
>> +        error_report("%s, KVM doesn't support gmem!", __func__);
>> +        exit(1);
>> +    }
> 
> We handle this special error case here,
> while the existing callers of kvm_set_user_memory_region handle the other error cases in different places.
> 
> Not that the rest of kvm-all does an excellent job at error handling, but maybe we can avoid compounding on the issue.

I'm not sure how to align them. Do you have any suggestion?

>> +
>>       mem.slot = slot->slot | (kml->as_id << 16);
>>       mem.guest_phys_addr = slot->start_addr;
>>       mem.userspace_addr = (unsigned long)slot->ram;
>>       mem.flags = slot->flags;
>> +    mem.gmem_fd = slot->fd;
>> +    mem.gmem_offset = slot->ofs;
>>   
>> -    if (slot->memory_size && !new && (mem.flags ^ slot->old_flags) & KVM_MEM_READONLY) {
>> +    if (slot->memory_size && !new && (slot->flags ^ slot->old_flags) & KVM_MEM_READONLY) {
> 
> Why the change if mem.flags == slot->flags ?

I guess the goal is to make it clearer that it's comparing the (new) 
flags with old_flags of the slot.

Anyway, if this change is annoying, I can drop it. :)

>>           /* Set the slot size to 0 before setting the slot to the desired
>>            * value. This is needed based on KVM commit 75d61fbc. */
>>           mem.memory_size = 0;
>> -        ret = kvm_vm_ioctl(s, KVM_SET_USER_MEMORY_REGION, &mem);
>> +
>> +        if (cap_user_memory2) {
>> +            ret = kvm_vm_ioctl(s, KVM_SET_USER_MEMORY_REGION2, &mem);
>> +        } else {
>> +            ret = kvm_vm_ioctl(s, KVM_SET_USER_MEMORY_REGION, &mem);
>> +	    }
>>           if (ret < 0) {
>>               goto err;
>>           }
>>       }
>>       mem.memory_size = slot->memory_size;
>> -    ret = kvm_vm_ioctl(s, KVM_SET_USER_MEMORY_REGION, &mem);
>> +    if (cap_user_memory2) {
>> +        ret = kvm_vm_ioctl(s, KVM_SET_USER_MEMORY_REGION2, &mem);
>> +    } else {
>> +        ret = kvm_vm_ioctl(s, KVM_SET_USER_MEMORY_REGION, &mem);
>> +    }
>>       slot->old_flags = mem.flags;
>>   err:
>>       trace_kvm_set_user_memory(mem.slot >> 16, (uint16_t)mem.slot, mem.flags,
>>                                 mem.guest_phys_addr, mem.memory_size,
>> -                              mem.userspace_addr, ret);
>> +                              mem.userspace_addr, mem.gmem_fd,
>> +			      mem.gmem_offset, ret);
>>       if (ret < 0) {
>> -        error_report("%s: KVM_SET_USER_MEMORY_REGION failed, slot=%d,"
>> -                     " start=0x%" PRIx64 ", size=0x%" PRIx64 ": %s",
>> -                     __func__, mem.slot, slot->start_addr,
>> -                     (uint64_t)mem.memory_size, strerror(errno));
>> +        if (cap_user_memory2) {
>> +                error_report("%s: KVM_SET_USER_MEMORY_REGION2 failed, slot=%d,"
>> +                        " start=0x%" PRIx64 ", size=0x%" PRIx64 ","
>> +                        " flags=0x%" PRIx32 ","
>> +                        " gmem_fd=%" PRId32 ", gmem_offset=0x%" PRIx64 ": %s",
>> +                        __func__, mem.slot, slot->start_addr,
>> +                (uint64_t)mem.memory_size, mem.flags,
>> +                        mem.gmem_fd, (uint64_t)mem.gmem_offset,
>> +                        strerror(errno));
>> +        } else {
>> +                error_report("%s: KVM_SET_USER_MEMORY_REGION failed, slot=%d,"
>> +                            " start=0x%" PRIx64 ", size=0x%" PRIx64 ": %s",
>> +                __func__, mem.slot, slot->start_addr,
>> +                (uint64_t)mem.memory_size, strerror(errno));
>> +        }
>>       }
>>       return ret;
>>   }
>> @@ -472,6 +505,9 @@ static int kvm_mem_flags(MemoryRegion *mr)
>>       if (readonly && kvm_readonly_mem_allowed) {
>>           flags |= KVM_MEM_READONLY;
>>       }
>> +    if (memory_region_can_be_private(mr)) {
>> +        flags |= KVM_MEM_PRIVATE;
>> +    }
>>       return flags;
>>   }
>>   
>> @@ -1402,6 +1438,9 @@ static void kvm_set_phys_mem(KVMMemoryListener *kml,
>>           mem->ram_start_offset = ram_start_offset;
>>           mem->ram = ram;
>>           mem->flags = kvm_mem_flags(mr);
>> +        mem->fd = mr->ram_block->gmem_fd;
>> +        mem->ofs = (uint8_t*)ram - mr->ram_block->host;
>> +
>>           kvm_slot_init_dirty_bitmap(mem);
>>           err = kvm_set_user_memory_region(kml, mem, true);
>>           if (err) {
>> diff --git a/accel/kvm/trace-events b/accel/kvm/trace-events
>> index 14ebfa1b991c..80694683acea 100644
>> --- a/accel/kvm/trace-events
>> +++ b/accel/kvm/trace-events
>> @@ -15,7 +15,7 @@ kvm_irqchip_update_msi_route(int virq) "Updating MSI route virq=%d"
>>   kvm_irqchip_release_virq(int virq) "virq %d"
>>   kvm_set_ioeventfd_mmio(int fd, uint64_t addr, uint32_t val, bool assign, uint32_t size, bool datamatch) "fd: %d @0x%" PRIx64 " val=0x%x assign: %d size: %d match: %d"
>>   kvm_set_ioeventfd_pio(int fd, uint16_t addr, uint32_t val, bool assign, uint32_t size, bool datamatch) "fd: %d @0x%x val=0x%x assign: %d size: %d match: %d"
>> -kvm_set_user_memory(uint16_t as, uint16_t slot, uint32_t flags, uint64_t guest_phys_addr, uint64_t memory_size, uint64_t userspace_addr, int ret) "AddrSpace#%d Slot#%d flags=0x%x gpa=0x%"PRIx64 " size=0x%"PRIx64 " ua=0x%"PRIx64 " ret=%d"
>> +kvm_set_user_memory(uint16_t as, uint16_t slot, uint32_t flags, uint64_t guest_phys_addr, uint64_t memory_size, uint64_t userspace_addr, uint32_t fd, uint64_t fd_offset, int ret) "AddrSpace#%d Slot#%d flags=0x%x gpa=0x%"PRIx64 " size=0x%"PRIx64 " ua=0x%"PRIx64 " gmem_fd=%d" " gmem_fd_offset=0x%" PRIx64 " ret=%d"
>>   kvm_clear_dirty_log(uint32_t slot, uint64_t start, uint32_t size) "slot#%"PRId32" start 0x%"PRIx64" size 0x%"PRIx32
>>   kvm_resample_fd_notify(int gsi) "gsi %d"
>>   kvm_dirty_ring_full(int id) "vcpu %d"
>> diff --git a/include/sysemu/kvm_int.h b/include/sysemu/kvm_int.h
>> index 511b42bde5c4..48220c0793ac 100644
>> --- a/include/sysemu/kvm_int.h
>> +++ b/include/sysemu/kvm_int.h
>> @@ -30,6 +30,8 @@ typedef struct KVMSlot
>>       int as_id;
>>       /* Cache of the offset in ram address space */
>>       ram_addr_t ram_start_offset;
>> +    int fd;
>> +    hwaddr ofs;
>>   } KVMSlot;
>>   
>>   typedef struct KVMMemoryUpdate {
>
diff mbox series

Patch

diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index d8eee405de24..7b1818334ba7 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -288,35 +288,68 @@  int kvm_physical_memory_addr_from_host(KVMState *s, void *ram,
 static int kvm_set_user_memory_region(KVMMemoryListener *kml, KVMSlot *slot, bool new)
 {
     KVMState *s = kvm_state;
-    struct kvm_userspace_memory_region mem;
+    struct kvm_userspace_memory_region2 mem;
+    static int cap_user_memory2 = -1;
     int ret;
 
+    if (cap_user_memory2 == -1) {
+        cap_user_memory2 = kvm_check_extension(s, KVM_CAP_USER_MEMORY2);
+    }
+
+    if (!cap_user_memory2 && slot->fd >= 0) {
+        error_report("%s, KVM doesn't support gmem!", __func__);
+        exit(1);
+    }
+
     mem.slot = slot->slot | (kml->as_id << 16);
     mem.guest_phys_addr = slot->start_addr;
     mem.userspace_addr = (unsigned long)slot->ram;
     mem.flags = slot->flags;
+    mem.gmem_fd = slot->fd;
+    mem.gmem_offset = slot->ofs;
 
-    if (slot->memory_size && !new && (mem.flags ^ slot->old_flags) & KVM_MEM_READONLY) {
+    if (slot->memory_size && !new && (slot->flags ^ slot->old_flags) & KVM_MEM_READONLY) {
         /* Set the slot size to 0 before setting the slot to the desired
          * value. This is needed based on KVM commit 75d61fbc. */
         mem.memory_size = 0;
-        ret = kvm_vm_ioctl(s, KVM_SET_USER_MEMORY_REGION, &mem);
+
+        if (cap_user_memory2) {
+            ret = kvm_vm_ioctl(s, KVM_SET_USER_MEMORY_REGION2, &mem);
+        } else {
+            ret = kvm_vm_ioctl(s, KVM_SET_USER_MEMORY_REGION, &mem);
+	    }
         if (ret < 0) {
             goto err;
         }
     }
     mem.memory_size = slot->memory_size;
-    ret = kvm_vm_ioctl(s, KVM_SET_USER_MEMORY_REGION, &mem);
+    if (cap_user_memory2) {
+        ret = kvm_vm_ioctl(s, KVM_SET_USER_MEMORY_REGION2, &mem);
+    } else {
+        ret = kvm_vm_ioctl(s, KVM_SET_USER_MEMORY_REGION, &mem);
+    }
     slot->old_flags = mem.flags;
 err:
     trace_kvm_set_user_memory(mem.slot >> 16, (uint16_t)mem.slot, mem.flags,
                               mem.guest_phys_addr, mem.memory_size,
-                              mem.userspace_addr, ret);
+                              mem.userspace_addr, mem.gmem_fd,
+			      mem.gmem_offset, ret);
     if (ret < 0) {
-        error_report("%s: KVM_SET_USER_MEMORY_REGION failed, slot=%d,"
-                     " start=0x%" PRIx64 ", size=0x%" PRIx64 ": %s",
-                     __func__, mem.slot, slot->start_addr,
-                     (uint64_t)mem.memory_size, strerror(errno));
+        if (cap_user_memory2) {
+                error_report("%s: KVM_SET_USER_MEMORY_REGION2 failed, slot=%d,"
+                        " start=0x%" PRIx64 ", size=0x%" PRIx64 ","
+                        " flags=0x%" PRIx32 ","
+                        " gmem_fd=%" PRId32 ", gmem_offset=0x%" PRIx64 ": %s",
+                        __func__, mem.slot, slot->start_addr,
+                (uint64_t)mem.memory_size, mem.flags,
+                        mem.gmem_fd, (uint64_t)mem.gmem_offset,
+                        strerror(errno));
+        } else {
+                error_report("%s: KVM_SET_USER_MEMORY_REGION failed, slot=%d,"
+                            " start=0x%" PRIx64 ", size=0x%" PRIx64 ": %s",
+                __func__, mem.slot, slot->start_addr,
+                (uint64_t)mem.memory_size, strerror(errno));
+        }
     }
     return ret;
 }
@@ -472,6 +505,9 @@  static int kvm_mem_flags(MemoryRegion *mr)
     if (readonly && kvm_readonly_mem_allowed) {
         flags |= KVM_MEM_READONLY;
     }
+    if (memory_region_can_be_private(mr)) {
+        flags |= KVM_MEM_PRIVATE;
+    }
     return flags;
 }
 
@@ -1402,6 +1438,9 @@  static void kvm_set_phys_mem(KVMMemoryListener *kml,
         mem->ram_start_offset = ram_start_offset;
         mem->ram = ram;
         mem->flags = kvm_mem_flags(mr);
+        mem->fd = mr->ram_block->gmem_fd;
+        mem->ofs = (uint8_t*)ram - mr->ram_block->host;
+
         kvm_slot_init_dirty_bitmap(mem);
         err = kvm_set_user_memory_region(kml, mem, true);
         if (err) {
diff --git a/accel/kvm/trace-events b/accel/kvm/trace-events
index 14ebfa1b991c..80694683acea 100644
--- a/accel/kvm/trace-events
+++ b/accel/kvm/trace-events
@@ -15,7 +15,7 @@  kvm_irqchip_update_msi_route(int virq) "Updating MSI route virq=%d"
 kvm_irqchip_release_virq(int virq) "virq %d"
 kvm_set_ioeventfd_mmio(int fd, uint64_t addr, uint32_t val, bool assign, uint32_t size, bool datamatch) "fd: %d @0x%" PRIx64 " val=0x%x assign: %d size: %d match: %d"
 kvm_set_ioeventfd_pio(int fd, uint16_t addr, uint32_t val, bool assign, uint32_t size, bool datamatch) "fd: %d @0x%x val=0x%x assign: %d size: %d match: %d"
-kvm_set_user_memory(uint16_t as, uint16_t slot, uint32_t flags, uint64_t guest_phys_addr, uint64_t memory_size, uint64_t userspace_addr, int ret) "AddrSpace#%d Slot#%d flags=0x%x gpa=0x%"PRIx64 " size=0x%"PRIx64 " ua=0x%"PRIx64 " ret=%d"
+kvm_set_user_memory(uint16_t as, uint16_t slot, uint32_t flags, uint64_t guest_phys_addr, uint64_t memory_size, uint64_t userspace_addr, uint32_t fd, uint64_t fd_offset, int ret) "AddrSpace#%d Slot#%d flags=0x%x gpa=0x%"PRIx64 " size=0x%"PRIx64 " ua=0x%"PRIx64 " gmem_fd=%d" " gmem_fd_offset=0x%" PRIx64 " ret=%d"
 kvm_clear_dirty_log(uint32_t slot, uint64_t start, uint32_t size) "slot#%"PRId32" start 0x%"PRIx64" size 0x%"PRIx32
 kvm_resample_fd_notify(int gsi) "gsi %d"
 kvm_dirty_ring_full(int id) "vcpu %d"
diff --git a/include/sysemu/kvm_int.h b/include/sysemu/kvm_int.h
index 511b42bde5c4..48220c0793ac 100644
--- a/include/sysemu/kvm_int.h
+++ b/include/sysemu/kvm_int.h
@@ -30,6 +30,8 @@  typedef struct KVMSlot
     int as_id;
     /* Cache of the offset in ram address space */
     ram_addr_t ram_start_offset;
+    int fd;
+    hwaddr ofs;
 } KVMSlot;
 
 typedef struct KVMMemoryUpdate {