kernel.git/virt/kvm/arm/arm.c, branch linux-4.14.y

KVM: arm/arm64: Sync ICH_VMCR_EL2 back when about to block

2019-08-25T08:50:18Z

commit 5eeaf10eec394b28fad2c58f1f5c3a5da0e87d1c upstream. Since commit commit 328e56647944 ("KVM: arm/arm64: vgic: Defer touching GICH_VMCR to vcpu_load/put"), we leave ICH_VMCR_EL2 (or its GICv2 equivalent) loaded as long as we can, only syncing it back when we're scheduled out. There is a small snag with that though: kvm_vgic_vcpu_pending_irq(), which is indirectly called from kvm_vcpu_check_block(), needs to evaluate the guest's view of ICC_PMR_EL1. At the point were we call kvm_vcpu_check_block(), the vcpu is still loaded, and whatever changes to PMR is not visible in memory until we do a vcpu_put(). Things go really south if the guest does the following: mov x0, #0 // or any small value masking interrupts msr ICC_PMR_EL1, x0 [vcpu preempted, then rescheduled, VMCR sampled] mov x0, #ff // allow all interrupts msr ICC_PMR_EL1, x0 wfi // traps to EL2, so samping of VMCR [interrupt arrives just after WFI] Here, the hypervisor's view of PMR is zero, while the guest has enabled its interrupts. kvm_vgic_vcpu_pending_irq() will then say that no interrupts are pending (despite an interrupt being received) and we'll block for no reason. If the guest doesn't have a periodic interrupt firing once it has blocked, it will stay there forever. To avoid this unfortuante situation, let's resync VMCR from kvm_arch_vcpu_blocking(), ensuring that a following kvm_vcpu_check_block() will observe the latest value of PMR. This has been found by booting an arm64 Linux guest with the pseudo NMI feature, and thus using interrupt priorities to mask interrupts instead of the usual PSTATE masking. Cc: stable@vger.kernel.org # 4.12 Fixes: 328e56647944 ("KVM: arm/arm64: vgic: Defer touching GICH_VMCR to vcpu_load/put") Signed-off-by: Marc Zyngier Signed-off-by: Greg Kroah-Hartman

KVM: s390: Do not report unusabled IDs via KVM_CAP_MAX_VCPU_ID

2019-06-09T07:18:16Z

commit a86cb413f4bf273a9d341a3ab2c2ca44e12eb317 upstream. KVM_CAP_MAX_VCPU_ID is currently always reporting KVM_MAX_VCPU_ID on all architectures. However, on s390x, the amount of usable CPUs is determined during runtime - it is depending on the features of the machine the code is running on. Since we are using the vcpu_id as an index into the SCA structures that are defined by the hardware (see e.g. the sca_add_vcpu() function), it is not only the amount of CPUs that is limited by the hard- ware, but also the range of IDs that we can use. Thus KVM_CAP_MAX_VCPU_ID must be determined during runtime on s390x, too. So the handling of KVM_CAP_MAX_VCPU_ID has to be moved from the common code into the architecture specific code, and on s390x we have to return the same value here as for KVM_CAP_MAX_VCPUS. This problem has been discovered with the kvm_create_max_vcpus selftest. With this change applied, the selftest now passes on s390x, too. Reviewed-by: Andrew Jones Reviewed-by: Cornelia Huck Reviewed-by: David Hildenbrand Signed-off-by: Thomas Huth Message-Id: <20190523164309.13345-9-thuth@redhat.com> Cc: stable@vger.kernel.org Signed-off-by: Christian Borntraeger Signed-off-by: Greg Kroah-Hartman

KVM: arm/arm64: Ensure vcpu target is unset on reset failure

2019-05-25T16:25:35Z

[ Upstream commit 811328fc3222f7b55846de0cd0404339e2e1e6d7 ] A failed KVM_ARM_VCPU_INIT should not set the vcpu target, as the vcpu target is used by kvm_vcpu_initialized() to determine if other vcpu ioctls may proceed. We need to set the target before calling kvm_reset_vcpu(), but if that call fails, we should then unset it and clear the feature bitmap while we're at it. Signed-off-by: Andrew Jones [maz: Simplified patch, completed commit message] Signed-off-by: Marc Zyngier Signed-off-by: Sasha Levin

KVM: arm/arm64: Fix VMID alloc race by reverting to lock-less

2019-01-16T21:07:13Z

commit fb544d1ca65a89f7a3895f7531221ceeed74ada7 upstream. We recently addressed a VMID generation race by introducing a read/write lock around accesses and updates to the vmid generation values. However, kvm_arch_vcpu_ioctl_run() also calls need_new_vmid_gen() but does so without taking the read lock. As far as I can tell, this can lead to the same kind of race: VM 0, VCPU 0 VM 0, VCPU 1 ------------ ------------ update_vttbr (vmid 254) update_vttbr (vmid 1) // roll over read_lock(kvm_vmid_lock); force_vm_exit() local_irq_disable need_new_vmid_gen == false //because vmid gen matches enter_guest (vmid 254) kvm_arch.vttbr = : read_unlock(kvm_vmid_lock); enter_guest (vmid 1) Which results in running two VCPUs in the same VM with different VMIDs and (even worse) other VCPUs from other VMs could now allocate clashing VMID 254 from the new generation as long as VCPU 0 is not exiting. Attempt to solve this by making sure vttbr is updated before another CPU can observe the updated VMID generation. Cc: stable@vger.kernel.org Fixes: f0cf47d939d0 "KVM: arm/arm64: Close VMID generation race" Reviewed-by: Julien Thierry Signed-off-by: Christoffer Dall Signed-off-by: Marc Zyngier Signed-off-by: Greg Kroah-Hartman

KVM: arm64: Fix caching of host MDCR_EL2 value

2018-11-13T19:15:08Z

commit da5a3ce66b8bb51b0ea8a89f42aac153903f90fb upstream. At boot time, KVM stashes the host MDCR_EL2 value, but only does this when the kernel is not running in hyp mode (i.e. is non-VHE). In these cases, the stashed value of MDCR_EL2.HPMN happens to be zero, which can lead to CONSTRAINED UNPREDICTABLE behaviour. Since we use this value to derive the MDCR_EL2 value when switching to/from a guest, after a guest have been run, the performance counters do not behave as expected. This has been observed to result in accesses via PMXEVTYPER_EL0 and PMXEVCNTR_EL0 not affecting the relevant counters, resulting in events not being counted. In these cases, only the fixed-purpose cycle counter appears to work as expected. Fix this by always stashing the host MDCR_EL2 value, regardless of VHE. Cc: Christopher Dall Cc: James Morse Cc: Will Deacon Cc: stable@vger.kernel.org Fixes: 1e947bad0b63b351 ("arm64: KVM: Skip HYP setup when already running in HYP") Tested-by: Robin Murphy Signed-off-by: Mark Rutland Signed-off-by: Marc Zyngier Signed-off-by: Greg Kroah-Hartman

arm64: KVM: Add ARCH_WORKAROUND_2 support for guests

2018-07-22T12:28:51Z

commit 55e3748e8902ff641e334226bdcb432f9a5d78d3 upstream. In order to offer ARCH_WORKAROUND_2 support to guests, we need a bit of infrastructure. Let's add a flag indicating whether or not the guest uses SSBD mitigation. Depending on the state of this flag, allow KVM to disable ARCH_WORKAROUND_2 before entering the guest, and enable it when exiting it. Reviewed-by: Christoffer Dall Reviewed-by: Mark Rutland Signed-off-by: Marc Zyngier Signed-off-by: Catalin Marinas Signed-off-by: Marc Zyngier Signed-off-by: Greg Kroah-Hartman

KVM: arm/arm64: Convert kvm_host_cpu_state to a static per-cpu allocation

2018-07-22T12:28:50Z

Commit 36989e7fd386a9a5822c48691473863f8fbb404d upstream. kvm_host_cpu_state is a per-cpu allocation made from kvm_arch_init() used to store the host EL1 registers when KVM switches to a guest. Make it easier for ASM to generate pointers into this per-cpu memory by making it a static allocation. Signed-off-by: James Morse Acked-by: Christoffer Dall Signed-off-by: Catalin Marinas Signed-off-by: Marc Zyngier Signed-off-by: Greg Kroah-Hartman

KVM: arm/arm64: Close VMID generation race

2018-05-01T19:58:22Z

commit f0cf47d939d0b4b4f660c5aaa4276fa3488f3391 upstream. Before entering the guest, we check whether our VMID is still part of the current generation. In order to avoid taking a lock, we start with checking that the generation is still current, and only if not current do we take the lock, recheck, and update the generation and VMID. This leaves open a small race: A vcpu can bump up the global generation number as well as the VM's, but has not updated the VMID itself yet. At that point another vcpu from the same VM comes in, checks the generation (and finds it not needing anything), and jumps into the guest. At this point, we end-up with two vcpus belonging to the same VM running with two different VMIDs. Eventually, the VMID used by the second vcpu will get reassigned, and things will really go wrong... A simple solution would be to drop this initial check, and always take the lock. This is likely to cause performance issues. A middle ground is to convert the spinlock to a rwlock, and only take the read lock on the fast path. If the check fails at that point, drop it and acquire the write lock, rechecking the condition. This ensures that the above scenario doesn't occur. Cc: stable@vger.kernel.org Reported-by: Mark Rutland Tested-by: Shannon Zhao Signed-off-by: Marc Zyngier Signed-off-by: Greg Kroah-Hartman

kvm: arm: don't treat unavailable HYP mode as an error

2018-02-25T10:07:55Z

[ Upstream commit 58d0d19a204604ca0da26058828a53558b265da3 ] Since it is perfectly legal to run the kernel at EL1, it is not actually an error if HYP mode is not available when attempting to initialize KVM, given that KVM support cannot be built as a module. So demote the kvm_err() to kvm_info(), which prevents the error from appearing on an otherwise 'quiet' console. Acked-by: Marc Zyngier Acked-by: Christoffer Dall Signed-off-by: Ard Biesheuvel Signed-off-by: Christoffer Dall Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

KVM: arm/arm64: Handle CPU_PM_ENTER_FAILED

2018-02-16T19:23:03Z

commit 58d6b15e9da5042a99c9c30ad725792e4569150e upstream. cpu_pm_enter() calls the pm notifier chain with CPU_PM_ENTER, then if there is a failure: CPU_PM_ENTER_FAILED. When KVM receives CPU_PM_ENTER it calls cpu_hyp_reset() which will return us to the hyp-stub. If we subsequently get a CPU_PM_ENTER_FAILED, KVM does nothing, leaving the CPU running with the hyp-stub, at odds with kvm_arm_hardware_enabled. Add CPU_PM_ENTER_FAILED as a fallthrough for CPU_PM_EXIT, this reloads KVM based on kvm_arm_hardware_enabled. This is safe even if CPU_PM_ENTER never gets as far as KVM, as cpu_hyp_reinit() calls cpu_hyp_reset() to make sure the hyp-stub is loaded before reloading KVM. Fixes: 67f691976662 ("arm64: kvm: allows kvm cpu hotplug") CC: Lorenzo Pieralisi Reviewed-by: Christoffer Dall Signed-off-by: James Morse Signed-off-by: Christoffer Dall Signed-off-by: Greg Kroah-Hartman