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

Xiaoyao Li
2023-12-04T06:48:41Z

On 11/18/2023 4:50 AM, Isaku Yamahata wrote:
> On Wed, Nov 15, 2023 at 02:14:14AM -0500,
> Xiaoyao Li <xiaoyao.li@intel.com> 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
>> backend'ed both by hva-based shared memory and guest memfd based private
>> memory.
>>
>> Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
>> Co-developed-by: Xiaoyao Li <xiaoyao.li@intel.com>
>> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
>> ---
>> 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.