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KVM: s390: fake memslot for ucontrol VMs

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Create a fake memslot for ucontrol VMs. The fake memslot identity-maps
userspace.

Now memslots will always be present, and ucontrol is not a special case
anymore.

Suggested-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
Link: https://lore.kernel.org/r/20250123144627.312456-4-imbrenda@linux.ibm.com
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Message-ID: <20250123144627.312456-4-imbrenda@linux.ibm.com>
This commit is contained in:
Claudio Imbrenda 2025-01-23 15:46:15 +01:00
parent decff09adb
commit 413c98f24c
4 changed files with 21 additions and 2 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
Documentation/virt/kvm/api.rst
View file

@ -1419,7 +1419,7 @@ fetch) is injected in the guest.
S390:
^^^^^
Returns -EINVAL if the VM has the KVM_VM_S390_UCONTROL flag set.
Returns -EINVAL or -EEXIST if the VM has the KVM_VM_S390_UCONTROL flag set.
Returns -EINVAL if called on a protected VM.
4.36 KVM_SET_TSS_ADDR

2
arch/s390/include/asm/kvm_host.h
View file

@ -30,6 +30,8 @@
#define KVM_S390_ESCA_CPU_SLOTS 248
#define KVM_MAX_VCPUS 255
#define KVM_INTERNAL_MEM_SLOTS 1
/*
* These seem to be used for allocating ->chip in the routing table, which we
* don't use. 1 is as small as we can get to reduce the needed memory. If we

17
arch/s390/kvm/kvm-s390.c
View file

@ -3428,8 +3428,20 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
VM_EVENT(kvm, 3, "vm created with type %lu", type);
if (type & KVM_VM_S390_UCONTROL) {
struct kvm_userspace_memory_region2 fake_memslot = {
.slot = KVM_S390_UCONTROL_MEMSLOT,
.guest_phys_addr = 0,
.userspace_addr = 0,
.memory_size = ALIGN_DOWN(TASK_SIZE, _SEGMENT_SIZE),
.flags = 0,
};
kvm->arch.gmap = NULL;
kvm->arch.mem_limit = KVM_S390_NO_MEM_LIMIT;
/* one flat fake memslot covering the whole address-space */
mutex_lock(&kvm->slots_lock);
KVM_BUG_ON(kvm_set_internal_memslot(kvm, &fake_memslot), kvm);
mutex_unlock(&kvm->slots_lock);
} else {
if (sclp.hamax == U64_MAX)
kvm->arch.mem_limit = TASK_SIZE_MAX;
@ -5854,7 +5866,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
{
gpa_t size;
if (kvm_is_ucontrol(kvm))
if (kvm_is_ucontrol(kvm) && new->id < KVM_USER_MEM_SLOTS)
return -EINVAL;
/* When we are protected, we should not change the memory slots */
@ -5906,6 +5918,9 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
{
int rc = 0;
if (kvm_is_ucontrol(kvm))
return;
switch (change) {
case KVM_MR_DELETE:
rc = gmap_unmap_segment(kvm->arch.gmap, old->base_gfn * PAGE_SIZE,

2
arch/s390/kvm/kvm-s390.h
View file

@ -20,6 +20,8 @@
#include <asm/processor.h>
#include <asm/sclp.h>
#define KVM_S390_UCONTROL_MEMSLOT (KVM_USER_MEM_SLOTS + 0)
static inline void kvm_s390_fpu_store(struct kvm_run *run)
{
fpu_stfpc(&run->s.regs.fpc);