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KVM: s390: Implement KVM_PRE_FAULT_MEMORY

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Implement and enable the KVM_PRE_FAULT_MEMORY ioctl for s390.

Faulted-in pages will be marked as accessed, unlike x86, otherwise they
will trigger a minor fault when accessed. Avoiding such faults is one of
the points of KVM_PRE_FAULT_MEMORY.

Reviewed-by: Steffen Eiden <seiden@linux.ibm.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Message-ID: <20260527144358.186359-3-imbrenda@linux.ibm.com>
This commit is contained in:
Claudio Imbrenda 2026-05-27 16:43:55 +02:00
parent 499d2e4b75
commit bea77e83c0
2 changed files with 46 additions and 0 deletions
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1
arch/s390/kvm/Kconfig
View File

@ -30,6 +30,7 @@ config KVM
select KVM_VFIO
select VIRT_XFER_TO_GUEST_WORK
select KVM_MMU_LOCKLESS_AGING
select KVM_GENERIC_PRE_FAULT_MEMORY
help
Support hosting paravirtualized guest machines using the SIE
virtualization capability on the mainframe. This should work

45
arch/s390/kvm/kvm-s390.c
View File

@ -630,6 +630,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
case KVM_CAP_S390_USER_OPEREXEC:
case KVM_CAP_S390_KEYOP:
case KVM_CAP_S390_VSIE_ESAMODE:
case KVM_CAP_PRE_FAULT_MEMORY:
r = 1;
break;
case KVM_CAP_SET_GUEST_DEBUG2:
@ -5736,6 +5737,50 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
return;
}
/**
* kvm_arch_vcpu_pre_fault_memory() -- pre-fault and link gmap dat tables
* @vcpu: the vcpu that shall appear to have generated the fault-in.
* @range: the range that needs to be faulted in.
*
* The first page of the given range is faulted in and the corresponding gmap
* page tables are created, as if the given vCPU had performed a read
* operation.
* If the range starts outside any memslots, an error is returned. An error is
* also returned for UCONTROL VMs, which should instead use the
* KVM_S390_VCPU_FAULT ioctl.
*
* Return:
* * %-ENOENT if the range lies outside of a memslot.
* * %-EINVAL in case of invalid state (for example if the VM is UCONTROL).
* * %-EIO if errors happen while faulting-in the page (will trigger a warning
* in the caller).
* * other error codes < 0 in case of other errors.
* * otherwise a number > 0 of bytes that have been faulted in successfully.
*/
long kvm_arch_vcpu_pre_fault_memory(struct kvm_vcpu *vcpu, struct kvm_pre_fault_memory *range)
{
struct guest_fault f = { .gfn = gpa_to_gfn(range->gpa), };
gpa_t end;
int rc;
if (kvm_is_ucontrol(vcpu->kvm))
return -EINVAL;
rc = kvm_s390_faultin_gfn(vcpu, NULL, &f);
if (rc == PGM_ADDRESSING)
return -ENOENT;
if (rc > 0)
return -EIO;
if (rc < 0)
return rc;
if (f.ptep)
return PAGE_SIZE;
end = ALIGN(range->gpa + PAGE_SIZE, f.crste_region3 ? _REGION3_SIZE : HPAGE_SIZE);
return min(range->size, end - range->gpa);
}
/**
* kvm_test_age_gfn() - test young
* @kvm: the kvm instance