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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 3/20/24 09:39, Michael Roth wrote: > + 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); > + } It's easier and more robust (for error reporting purposes) to check both KVM_CAP_GUEST_MEMFD and KVM_CAP_USER_MEMORY2 at once in the earlier patches: - kvm_guest_memfd_supported = kvm_check_extension(s, KVM_CAP_GUEST_MEMFD); + kvm_guest_memfd_supported = + kvm_check_extension(s, KVM_CAP_GUEST_MEMFD) && + kvm_check_extension(s, KVM_CAP_USER_MEMORY2); since KVM cannot really support guest_memfd if it cannot then use it to create private memory slots. And then, this one can be changed to also use kvm_guest_memfd_supported: diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c index e83429b31eb..afcf6f87045 100644 --- a/accel/kvm/kvm-all.c +++ b/accel/kvm/kvm-all.c @@ -284,19 +284,8 @@ static int kvm_set_user_memory_region(KVMMemoryListener *kml, KVMSlot *slot, boo { KVMState *s = kvm_state; 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; @@ -309,7 +298,7 @@ static int kvm_set_user_memory_region(KVMMemoryListener *kml, KVMSlot *slot, boo * value. This is needed based on KVM commit 75d61fbc. */ mem.memory_size = 0; - if (cap_user_memory2) { + if (kvm_guest_memfd_supported) { ret = kvm_vm_ioctl(s, KVM_SET_USER_MEMORY_REGION2, &mem); } else { ret = kvm_vm_ioctl(s, KVM_SET_USER_MEMORY_REGION, &mem); @@ -319,7 +308,7 @@ static int kvm_set_user_memory_region(KVMMemoryListener *kml, KVMSlot *slot, boo } } mem.memory_size = slot->memory_size; - if (cap_user_memory2) { + if (kvm_guest_memfd_supported) { ret = kvm_vm_ioctl(s, KVM_SET_USER_MEMORY_REGION2, &mem); } else { ret = kvm_vm_ioctl(s, KVM_SET_USER_MEMORY_REGION, &mem); @@ -331,7 +320,7 @@ err: mem.userspace_addr, mem.guest_memfd, mem.guest_memfd_offset, ret); if (ret < 0) { - if (cap_user_memory2) { + if (kvm_guest_memfd_supported) { error_report("%s: KVM_SET_USER_MEMORY_REGION2 failed, slot=%d," " start=0x%" PRIx64 ", size=0x%" PRIx64 "," " flags=0x%" PRIx32 ", guest_memfd=%" PRId32 "," @@ -501,6 +490,7 @@ static int kvm_mem_flags(MemoryRegion *mr) flags |= KVM_MEM_READONLY; } if (memory_region_has_guest_memfd(mr)) { + assert(kvm_guest_memfd_supported); flags |= KVM_MEM_GUEST_MEMFD; } return flags;