KVM: s390: Make huge pages unavailable in ucontrol VMs (40ebdb8e) · Commits · 戴 / test

We currently do not notify all gmaps when using gmap_pmdp_xchg(), due to locking constraints. This makes ucontrol VMs, which is the only VM type that creates multiple gmaps, incompatible with huge pages. Also we would need to hold the guest_table_lock of all gmaps that have this vmaddr maped to synchronize access to the pmd. ucontrol VMs are rather exotic and creating a new locking concept is no easy task. Hence we return EINVAL when trying to active KVM_CAP_S390_HPAGE_1M and report it as being not available when checking for it. Fixes: ("KVM: s390: Add huge page enablement control") Signed-off-by:

Janosch Frank <frankja@linux.ibm.com> Reviewed-by:

David Hildenbrand <david@redhat.com> Reviewed-by:

Claudio Imbrenda <imbrenda@linux.ibm.com> Message-Id: <20180801112508.138159-1-frankja@linux.ibm.com> Signed-off-by:

Janosch Frank <frankja@linux.ibm.com>

Documentation/virtual/kvm/api.txt

+2 −1

Original line number	Diff line number	Diff line
		@@ -4510,7 +4510,8 @@ Do not enable KVM_FEATURE_PV_UNHALT if you disable HLT exits.
		Architectures: s390
		Parameters: none
		Returns: 0 on success, -EINVAL if hpage module parameter was not set
		or cmma is enabled
		or cmma is enabled, or the VM has the KVM_VM_S390_UCONTROL
		flag set

		With this capability the KVM support for memory backing with 1m pages
		through hugetlbfs can be enabled for a VM. After the capability is

arch/s390/kvm/kvm-s390.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -481,7 +481,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
		break;
		case KVM_CAP_S390_HPAGE_1M:
		r = 0;
		if (hpage)
		if (hpage && !kvm_is_ucontrol(kvm))
		r = 1;
		break;
		case KVM_CAP_S390_MEM_OP:
		@@ -691,7 +691,7 @@ static int kvm_vm_ioctl_enable_cap(struct kvm kvm, struct kvm_enable_cap cap)
		mutex_lock(&kvm->lock);
		if (kvm->created_vcpus)
		r = -EBUSY;
		else if (!hpage \|\| kvm->arch.use_cmma)
		else if (!hpage \|\| kvm->arch.use_cmma \|\| kvm_is_ucontrol(kvm))
		r = -EINVAL;
		else {
		r = 0;

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