Re: [PATCH v3 05/70] kvm: Enable KVM_SET_USER_MEMORY_REGION2 for memslot

[Xiaoyao Li]

On 11/18/2023 4:50 AM, Isaku Yamahata wrote:

On Wed, Nov 15, 2023 at 02:14:14AM -0500,
Xiaoyao Li  wrote:


From: Chao Peng 

Switch to KVM_SET_USER_MEMORY_REGION2 when supported by KVM.

With KVM_SET_USER_MEMORY_REGION2, QEMU can set up memory region that
backend'ed both by hva-based shared memory and guest memfd based private
memory.

Signed-off-by: Chao Peng 
Co-developed-by: Xiaoyao Li 
Signed-off-by: Xiaoyao Li 
---
  accel/kvm/kvm-all.c  | 56 ++--
  accel/kvm/trace-events   |  2 +-
  include/sysemu/kvm_int.h |  2 ++
  3 files changed, 51 insertions(+), 9 deletions(-)

diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index 9f751d4971f8..69afeb47c9c0 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -293,35 +293,69 @@ 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->guest_memfd >= 0) {
+error_report("%s, KVM doesn't support KVM_CAP_USER_MEMORY2,"
+ " which is required by guest memfd!", __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.guest_memfd = slot->guest_memfd;
+mem.guest_memfd_offset = slot->guest_memfd_offset;
  
  if (slot->memory_size && !new && (mem.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.guest_memfd,
+  mem.guest_memfd_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 ", guest_memfd=%" PRId32 ","
+" guest_memfd_offset=0x%" PRIx64 ": %s",
+__func__, mem.slot, slot->start_addr,
+(uint64_t)mem.memory_size, mem.flags,
+mem.guest_memfd, (uint64_t)mem.guest_memfd_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;
  }
@@ -477,6 +511,9 @@ static int kvm_mem_flags(MemoryRegion *mr)
  if (readonly && kvm_readonly_mem_allowed) {
  flags |= KVM_MEM_READONLY;
  }
+if (memory_region_has_guest_memfd(mr)) {
+flags |= KVM_MEM_PRIVATE;
+}


Nitpick: it was renamed to KVM_MEM_GUEST_MEMFD
As long as the value is defined to same value, it doesn't matter, though.


thanks for the reminder!

Will update the headers and switch to KVM_MEM_GUEST_MEMFD.

Re: [PATCH v3 05/70] kvm: Enable KVM_SET_USER_MEMORY_REGION2 for memslot

[Isaku Yamahata]

On Wed, Nov 15, 2023 at 02:14:14AM -0500,
Xiaoyao Li  wrote:

> From: Chao Peng 
> 
> Switch to KVM_SET_USER_MEMORY_REGION2 when supported by KVM.
> 
> With KVM_SET_USER_MEMORY_REGION2, QEMU can set up memory region that
> backend'ed both by hva-based shared memory and guest memfd based private
> memory.
> 
> Signed-off-by: Chao Peng 
> Co-developed-by: Xiaoyao Li 
> Signed-off-by: Xiaoyao Li 
> ---
>  accel/kvm/kvm-all.c  | 56 ++--
>  accel/kvm/trace-events   |  2 +-
>  include/sysemu/kvm_int.h |  2 ++
>  3 files changed, 51 insertions(+), 9 deletions(-)
> 
> diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
> index 9f751d4971f8..69afeb47c9c0 100644
> --- a/accel/kvm/kvm-all.c
> +++ b/accel/kvm/kvm-all.c
> @@ -293,35 +293,69 @@ 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->guest_memfd >= 0) {
> +error_report("%s, KVM doesn't support KVM_CAP_USER_MEMORY2,"
> + " which is required by guest memfd!", __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.guest_memfd = slot->guest_memfd;
> +mem.guest_memfd_offset = slot->guest_memfd_offset;
>  
>  if (slot->memory_size && !new && (mem.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.guest_memfd,
> +  mem.guest_memfd_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 ", guest_memfd=%" PRId32 ","
> +" guest_memfd_offset=0x%" PRIx64 ": %s",
> +__func__, mem.slot, slot->start_addr,
> +(uint64_t)mem.memory_size, mem.flags,
> +mem.guest_memfd, (uint64_t)mem.guest_memfd_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;
>  }
> @@ -477,6 +511,9 @@ static int kvm_mem_flags(MemoryRegion *mr)
>  if (readonly && kvm_readonly_mem_allowed) {
>  flags |= KVM_MEM_READONLY;
>  }
> +if (memory_region_has_guest_memfd(mr)) {
> +flags |= KVM_MEM_PRIVATE;
> +}

Nitpick: it was renamed to KVM_MEM_GUEST_MEMFD
As long as the value is defined to same value, it doesn't matter, though.
-- 
Isaku Yamahata