[GIT PULL 3/3] kvm: s390: Reject memory region operations for ucontrol VMs

Janosch Frank
2024-07-11T11:08:38Z

From: Christoph Schlameuss <schlameuss@linux.ibm.com>

This change rejects the KVM_SET_USER_MEMORY_REGION and
KVM_SET_USER_MEMORY_REGION2 ioctls when called on a ucontrol VM.
This is necessary since ucontrol VMs have kvm->arch.gmap set to 0 and
would thus result in a null pointer dereference further in.
Memory management needs to be performed in userspace and using the
ioctls KVM_S390_UCAS_MAP and KVM_S390_UCAS_UNMAP.

Also improve s390 specific documentation for KVM_SET_USER_MEMORY_REGION
and KVM_SET_USER_MEMORY_REGION2.

Signed-off-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
Fixes: 27e0393f15fc ("KVM: s390: ucontrol: per vcpu address spaces")
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Link: https://lore.kernel.org/r/20240624095902.29375-1-schlameuss@linux.ibm.com
Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
[frankja@linux.ibm.com: commit message spelling fix, subject prefix fix]
Message-ID: <20240624095902.29375-1-schlameuss@linux.ibm.com>
---
Documentation/virt/kvm/api.rst | 12 ++++++++++++
arch/s390/kvm/kvm-s390.c | 3 +++
2 files changed, 15 insertions(+)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index a71d91978d9e..eec8df1dde06 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -1403,6 +1403,12 @@ Instead, an abort (data abort if the cause of the page-table update
was a load or a store, instruction abort if it was an instruction
fetch) is injected in the guest.

+S390:
+^^^^^
+
+Returns -EINVAL 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
---------------------

@@ -6273,6 +6279,12 @@ state. At VM creation time, all memory is shared, i.e. the PRIVATE attribute
is '0' for all gfns. Userspace can control whether memory is shared/private by
toggling KVM_MEMORY_ATTRIBUTE_PRIVATE via KVM_SET_MEMORY_ATTRIBUTES as needed.

+S390:
+^^^^^
+
+Returns -EINVAL if the VM has the KVM_VM_S390_UCONTROL flag set.
+Returns -EINVAL if called on a protected VM.
+
4.141 KVM_SET_MEMORY_ATTRIBUTES
-------------------------------

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 82e9631cd9ef..854d0d1410be 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -5748,6 +5748,9 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
{
gpa_t size;

+ if (kvm_is_ucontrol(kvm))
+ return -EINVAL;
+
/* When we are protected, we should not change the memory slots */
if (kvm_s390_pv_get_handle(kvm))
return -EINVAL;
--
2.45.2