From: Chao Peng <chao.p.p...@linux.intel.com>
Upon an KVM_EXIT_MEMORY_FAULT exit, userspace needs to do the memory
conversion on the RAMBlock to turn the memory into desired attribute,
switching between private and shared.
Currently only KVM_MEMORY_EXIT_FLAG_PRIVATE in flags is valid when
KVM_EXIT_MEMORY_FAULT happens.
Note, KVM_EXIT_MEMORY_FAULT makes sense only when the RAMBlock has
guest_memfd memory backend.
Note, KVM_EXIT_MEMORY_FAULT returns with -EFAULT, so special handling is
added.
When page is converted from shared to private, the original shared
memory can be discarded via ram_block_discard_range(). Note, shared
memory can be discarded only when it's not back'ed by hugetlb because
hugetlb is supposed to be pre-allocated and no need for discarding.
Signed-off-by: Chao Peng <chao.p.p...@linux.intel.com>
Co-developed-by: Xiaoyao Li <xiaoyao...@intel.com>
Signed-off-by: Xiaoyao Li <xiaoyao...@intel.com>
Message-ID: <20240320083945.991426-13-michael.r...@amd.com>
Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
---
include/sysemu/kvm.h | 2 +
accel/kvm/kvm-all.c | 98 +++++++++++++++++++++++++++++++++++++-----
accel/kvm/trace-events | 2 +
3 files changed, 92 insertions(+), 10 deletions(-)
diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
index 217f3fe17ba..47f9e8be1b3 100644
--- a/include/sysemu/kvm.h
+++ b/include/sysemu/kvm.h
@@ -542,4 +542,6 @@ 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);
+int kvm_convert_memory(hwaddr start, hwaddr size, bool to_private);
+
#endif
diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index f49b2b95b54..9eef2c64003 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -2900,6 +2900,69 @@ static void kvm_eat_signals(CPUState *cpu)
} while (sigismember(&chkset, SIG_IPI));
}
+int kvm_convert_memory(hwaddr start, hwaddr size, bool to_private)
+{
+ MemoryRegionSection section;
+ ram_addr_t offset;
+ MemoryRegion *mr;
+ RAMBlock *rb;
+ void *addr;
+ int ret = -1;
+
+ trace_kvm_convert_memory(start, size, to_private ? "shared_to_private" :
"private_to_shared");
+
+ if (!QEMU_PTR_IS_ALIGNED(start, qemu_real_host_page_size()) ||
+ !QEMU_PTR_IS_ALIGNED(size, qemu_real_host_page_size())) {
+ return -1;
+ }
+
+ if (!size) {
+ return -1;
+ }
+
+ section = memory_region_find(get_system_memory(), start, size);
+ mr = section.mr;
+ if (!mr) {
+ return -1;
+ }
+
+ if (!memory_region_has_guest_memfd(mr)) {
+ error_report("Converting non guest_memfd backed memory region "
+ "(0x%"HWADDR_PRIx" ,+ 0x%"HWADDR_PRIx") to %s",
+ start, size, to_private ? "private" : "shared");
+ goto out_unref;
+ }
+
+ if (to_private) {
+ ret = kvm_set_memory_attributes_private(start, size);
+ } else {
+ ret = kvm_set_memory_attributes_shared(start, size);
+ }
+ if (ret) {
+ goto out_unref;
+ }
+
+ addr = memory_region_get_ram_ptr(mr) + section.offset_within_region;
+ rb = qemu_ram_block_from_host(addr, false, &offset);
+
+ if (to_private) {
+ if (rb->page_size != qemu_real_host_page_size()) {
+ /*
+ * shared memory is backed by hugetlb, which is supposed to be
+ * pre-allocated and doesn't need to be discarded
+ */
+ goto out_unref;
+ }
+ ret = ram_block_discard_range(rb, offset, size);
+ } else {
+ ret = ram_block_discard_guest_memfd_range(rb, offset, size);
+ }
+
+out_unref:
+ memory_region_unref(mr);
+ return ret;
+}
+
int kvm_cpu_exec(CPUState *cpu)
{
struct kvm_run *run = cpu->kvm_run;
@@ -2967,18 +3030,20 @@ int kvm_cpu_exec(CPUState *cpu)
ret = EXCP_INTERRUPT;
break;
}
- fprintf(stderr, "error: kvm run failed %s\n",
- strerror(-run_ret));
+ if (!(run_ret == -EFAULT && run->exit_reason ==
KVM_EXIT_MEMORY_FAULT)) {
+ fprintf(stderr, "error: kvm run failed %s\n",
+ strerror(-run_ret));
#ifdef TARGET_PPC
- if (run_ret == -EBUSY) {
- fprintf(stderr,
- "This is probably because your SMT is enabled.\n"
- "VCPU can only run on primary threads with all "
- "secondary threads offline.\n");
- }
+ if (run_ret == -EBUSY) {
+ fprintf(stderr,
+ "This is probably because your SMT is enabled.\n"
+ "VCPU can only run on primary threads with all "
+ "secondary threads offline.\n");
+ }
#endif
- ret = -1;
- break;
+ ret = -1;
+ break;
+ }
}
trace_kvm_run_exit(cpu->cpu_index, run->exit_reason);
@@ -3061,6 +3126,19 @@ int kvm_cpu_exec(CPUState *cpu)
break;
}
break;
+ case KVM_EXIT_MEMORY_FAULT:
+ trace_kvm_memory_fault(run->memory_fault.gpa,
+ run->memory_fault.size,
+ run->memory_fault.flags);
+ if (run->memory_fault.flags & ~KVM_MEMORY_EXIT_FLAG_PRIVATE) {
+ error_report("KVM_EXIT_MEMORY_FAULT: Unknown flag 0x%" PRIx64,
+ (uint64_t)run->memory_fault.flags);
+ ret = -1;
+ break;
+ }
+ ret = kvm_convert_memory(run->memory_fault.gpa,
run->memory_fault.size,
+ run->memory_fault.flags &
KVM_MEMORY_EXIT_FLAG_PRIVATE);
+ break;
default:
ret = kvm_arch_handle_exit(cpu, run);
break;
diff --git a/accel/kvm/trace-events b/accel/kvm/trace-events
index e8c52cb9e7a..681ccb667d6 100644
--- a/accel/kvm/trace-events
+++ b/accel/kvm/trace-events
@@ -31,3 +31,5 @@ kvm_cpu_exec(void) ""
kvm_interrupt_exit_request(void) ""
kvm_io_window_exit(void) ""
kvm_run_exit_system_event(int cpu_index, uint32_t event_type) "cpu_index %d,
system_even_type %"PRIu32
+kvm_convert_memory(uint64_t start, uint64_t size, const char *msg) "start 0x%"
PRIx64 " size 0x%" PRIx64 " %s"
+kvm_memory_fault(uint64_t start, uint64_t size, uint64_t flags) "start 0x%"
PRIx64 " size 0x%" PRIx64 " flags 0x%" PRIx64
--
2.44.0
