If we cannot allocate the XIVE VPs in OPAL, the creation of a XIVE or XICS-on-XIVE device is aborted as expected, but we leave kvm->arch.xive set forever since the release method isn't called in this case. Any subsequent tentative to create a XIVE or XICS-on-XIVE for this VM will thus always fail (DoS). This is a problem for QEMU since it destroys and re-creates these devices when the VM is reset: the VM would be restricted to using the much slower emulated XIVE or XICS forever.
As an alternative to adding rollback, do not assign kvm->arch.xive before making sure the XIVE VPs are allocated in OPAL.
Cc: stable@vger.kernel.org # v5.2 Fixes: 5422e95103cf ("KVM: PPC: Book3S HV: XIVE: Replace the 'destroy' method by a 'release' method") Signed-off-by: Greg Kurz groug@kaod.org Reviewed-by: Cédric Le Goater clg@kaod.org --- arch/powerpc/kvm/book3s_xive.c | 11 +++++------ arch/powerpc/kvm/book3s_xive_native.c | 2 +- 2 files changed, 6 insertions(+), 7 deletions(-)
diff --git a/arch/powerpc/kvm/book3s_xive.c b/arch/powerpc/kvm/book3s_xive.c index 591bfb4bfd0f..99884662facb 100644 --- a/arch/powerpc/kvm/book3s_xive.c +++ b/arch/powerpc/kvm/book3s_xive.c @@ -1997,6 +1997,10 @@ static int kvmppc_xive_create(struct kvm_device *dev, u32 type)
pr_devel("Creating xive for partition\n");
+ /* Already there ? */ + if (kvm->arch.xive) + return -EEXIST; + xive = kvmppc_xive_get_device(kvm, type); if (!xive) return -ENOMEM; @@ -2006,12 +2010,6 @@ static int kvmppc_xive_create(struct kvm_device *dev, u32 type) xive->kvm = kvm; mutex_init(&xive->lock);
- /* Already there ? */ - if (kvm->arch.xive) - ret = -EEXIST; - else - kvm->arch.xive = xive; - /* We use the default queue size set by the host */ xive->q_order = xive_native_default_eq_shift(); if (xive->q_order < PAGE_SHIFT) @@ -2031,6 +2029,7 @@ static int kvmppc_xive_create(struct kvm_device *dev, u32 type) if (ret) return ret;
+ kvm->arch.xive = xive; return 0; }
diff --git a/arch/powerpc/kvm/book3s_xive_native.c b/arch/powerpc/kvm/book3s_xive_native.c index 248c1ea9e788..6b91c74839d5 100644 --- a/arch/powerpc/kvm/book3s_xive_native.c +++ b/arch/powerpc/kvm/book3s_xive_native.c @@ -1079,7 +1079,6 @@ static int kvmppc_xive_native_create(struct kvm_device *dev, u32 type) dev->private = xive; xive->dev = dev; xive->kvm = kvm; - kvm->arch.xive = xive; mutex_init(&xive->mapping_lock); mutex_init(&xive->lock);
@@ -1100,6 +1099,7 @@ static int kvmppc_xive_native_create(struct kvm_device *dev, u32 type) if (ret) return ret;
+ kvm->arch.xive = xive; return 0; }