From: Xiaoyao Li <[email protected]> With the mmap support of guest memfd, KVM allows userspace to create guest memfd serving as normal non-private memory for X86 DEFAULT VM. However, KVM doesn't support private memory attribute for X86 DEFAULT VM.
Make kvm_guest_memfd_supported not rely on KVM_MEMORY_ATTRIBUTE_PRIVATE and check KVM_MEMORY_ATTRIBUTE_PRIVATE separately when the machine requires guest_memfd to serve as private memory. This allows QEMU to create guest memfd with mmap to serve as the memory backend for X86 DEFAULT VM. Signed-off-by: Xiaoyao Li <[email protected]> Signed-off-by: Peter Xu <[email protected]> Reviewed-by: Fabiano Rosas <[email protected]> Reviewed-by: Michael Roth <[email protected]> Signed-off-by: Michael Roth <[email protected]> --- accel/kvm/kvm-all.c | 8 ++++++-- accel/stubs/kvm-stub.c | 5 +++++ include/system/kvm.h | 1 + system/physmem.c | 8 ++++++++ 4 files changed, 20 insertions(+), 2 deletions(-) diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c index 83cbd120a8..cdc7554082 100644 --- a/accel/kvm/kvm-all.c +++ b/accel/kvm/kvm-all.c @@ -1627,6 +1627,11 @@ int kvm_set_memory_attributes_shared(hwaddr start, uint64_t size) return kvm_set_memory_attributes(start, size, 0); } +bool kvm_private_memory_attribute_supported(void) +{ + return !!(kvm_supported_memory_attributes & KVM_MEMORY_ATTRIBUTE_PRIVATE); +} + /* Called with KVMMemoryListener.slots_lock held */ static void kvm_set_phys_mem(KVMMemoryListener *kml, MemoryRegionSection *section, bool add) @@ -3058,8 +3063,7 @@ static int kvm_init(AccelState *as, MachineState *ms) kvm_supported_memory_attributes = kvm_vm_check_extension(s, KVM_CAP_MEMORY_ATTRIBUTES); kvm_guest_memfd_supported = kvm_vm_check_extension(s, KVM_CAP_GUEST_MEMFD) && - kvm_vm_check_extension(s, KVM_CAP_USER_MEMORY2) && - (kvm_supported_memory_attributes & KVM_MEMORY_ATTRIBUTE_PRIVATE); + kvm_vm_check_extension(s, KVM_CAP_USER_MEMORY2); kvm_pre_fault_memory_supported = kvm_vm_check_extension(s, KVM_CAP_PRE_FAULT_MEMORY); if (s->kernel_irqchip_split == ON_OFF_AUTO_AUTO) { diff --git a/accel/stubs/kvm-stub.c b/accel/stubs/kvm-stub.c index 32b4b07403..3d34e3b99d 100644 --- a/accel/stubs/kvm-stub.c +++ b/accel/stubs/kvm-stub.c @@ -143,3 +143,8 @@ int kvm_create_guest_memfd(uint64_t size, uint64_t flags, Error **errp) { return -ENOSYS; } + +bool kvm_private_memory_attribute_supported(void) +{ + return false; +} diff --git a/include/system/kvm.h b/include/system/kvm.h index 714b8c7b01..d29624034c 100644 --- a/include/system/kvm.h +++ b/include/system/kvm.h @@ -551,6 +551,7 @@ int kvm_create_guest_memfd(uint64_t size, uint64_t flags, Error **errp); int kvm_set_memory_attributes_private(hwaddr start, uint64_t size); int kvm_set_memory_attributes_shared(hwaddr start, uint64_t size); +bool kvm_private_memory_attribute_supported(void); int kvm_convert_memory(hwaddr start, hwaddr size, bool to_private); diff --git a/system/physmem.c b/system/physmem.c index c21ea92915..406338f165 100644 --- a/system/physmem.c +++ b/system/physmem.c @@ -2192,6 +2192,14 @@ static void ram_block_add(RAMBlock *new_block, Error **errp) object_get_typename(OBJECT(current_machine->cgs))); goto out_free; } + + if (!kvm_private_memory_attribute_supported()) { + error_setg(errp, "cannot set up private guest memory for %s: " + "KVM does not support private memory attribute", + object_get_typename(OBJECT(current_machine->cgs))); + goto out_free; + } + assert(new_block->guest_memfd < 0); ret = ram_block_coordinated_discard_require(true); -- 2.43.0
