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kvm: handle KVM_EXIT_MEMORY_FAULT

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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.peng@linux.intel.com>
Co-developed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>

Message-ID: <20240320083945.991426-13-michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Chao Peng 2024-03-20 03:39:08 -05:00 committed by Paolo Bonzini
parent b2e9426c04
commit c15e568407
3 changed files with 92 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

78
accel/kvm/kvm-all.c
View File

@ -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;
@ -2967,6 +3030,7 @@ int kvm_cpu_exec(CPUState *cpu)
ret = EXCP_INTERRUPT;
break;
}
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
@ -2980,6 +3044,7 @@ int kvm_cpu_exec(CPUState *cpu)
ret = -1;
break;
}
}
trace_kvm_run_exit(cpu->cpu_index, run->exit_reason);
switch (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;

2
accel/kvm/trace-events
View File

@ -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
include/sysemu/kvm.h
View File

@ -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