kernel/arch/arm64/kvm/mmu.c, branch linux-6.2.y

KVM: arm64: Check for kvm_vma_mte_allowed in the critical section

2023-04-06T10:12:47Z

commit 8c2e8ac8ad4be68409e806ce1cc78fc7a04539f3 upstream. On page fault, we find about the VMA that backs the page fault early on, and quickly release the mmap_read_lock. However, using the VMA pointer after the critical section is pretty dangerous, as a teardown may happen in the meantime and the VMA be long gone. Move the sampling of the MTE permission early, and NULL-ify the VMA pointer after that, just to be on the safe side. Signed-off-by: Marc Zyngier Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20230316174546.3777507-3-maz@kernel.org Signed-off-by: Oliver Upton Signed-off-by: Greg Kroah-Hartman

KVM: arm64: Disable interrupts while walking userspace PTs

2023-04-06T10:12:47Z

commit e86fc1a3a3e9b4850fe74d738e3cfcf4297d8bba upstream. We walk the userspace PTs to discover what mapping size was used there. However, this can race against the userspace tables being freed, and we end-up in the weeds. Thankfully, the mm code is being generous and will IPI us when doing so. So let's implement our part of the bargain and disable interrupts around the walk. This ensures that nothing terrible happens during that time. We still need to handle the removal of the page tables before the walk. For that, allow get_user_mapping_size() to return an error, and make sure this error can be propagated all the way to the the exit handler. Signed-off-by: Marc Zyngier Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20230316174546.3777507-2-maz@kernel.org Signed-off-by: Oliver Upton Signed-off-by: Greg Kroah-Hartman

KVM: arm64: Retry fault if vma_lookup() results become invalid

2023-04-06T10:12:47Z

commit 13ec9308a85702af7c31f3638a2720863848a7f2 upstream. Read mmu_invalidate_seq before dropping the mmap_lock so that KVM can detect if the results of vma_lookup() (e.g. vma_shift) become stale before it acquires kvm->mmu_lock. This fixes a theoretical bug where a VMA could be changed by userspace after vma_lookup() and before KVM reads the mmu_invalidate_seq, causing KVM to install page table entries based on a (possibly) no-longer-valid vma_shift. Re-order the MMU cache top-up to earlier in user_mem_abort() so that it is not done after KVM has read mmu_invalidate_seq (i.e. so as to avoid inducing spurious fault retries). This bug has existed since KVM/ARM's inception. It's unlikely that any sane userspace currently modifies VMAs in such a way as to trigger this race. And even with directed testing I was unable to reproduce it. But a sufficiently motivated host userspace might be able to exploit this race. Fixes: 94f8e6418d39 ("KVM: ARM: Handle guest faults in KVM") Cc: stable@vger.kernel.org Reported-by: Sean Christopherson Signed-off-by: David Matlack Reviewed-by: Marc Zyngier Link: https://lore.kernel.org/r/20230313235454.2964067-1-dmatlack@google.com Signed-off-by: Oliver Upton Signed-off-by: Greg Kroah-Hartman

KVM: arm64: Convert FSC_* over to ESR_ELx_FSC_*

2023-01-03T10:01:52Z

The former is an AArch32 legacy, so let's move over to the verbose (and strictly identical) version. This involves moving some of the #defines that were private to KVM into the more generic esr.h. Signed-off-by: Marc Zyngier

Merge tag 'kvmarm-6.2' of https://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm into HEAD

2022-12-09T08:12:12Z

KVM/arm64 updates for 6.2 - Enable the per-vcpu dirty-ring tracking mechanism, together with an option to keep the good old dirty log around for pages that are dirtied by something other than a vcpu. - Switch to the relaxed parallel fault handling, using RCU to delay page table reclaim and giving better performance under load. - Relax the MTE ABI, allowing a VMM to use the MAP_SHARED mapping option, which multi-process VMMs such as crosvm rely on. - Merge the pKVM shadow vcpu state tracking that allows the hypervisor to have its own view of a vcpu, keeping that state private. - Add support for the PMUv3p5 architecture revision, bringing support for 64bit counters on systems that support it, and fix the no-quite-compliant CHAIN-ed counter support for the machines that actually exist out there. - Fix a handful of minor issues around 52bit VA/PA support (64kB pages only) as a prefix of the oncoming support for 4kB and 16kB pages. - Add/Enable/Fix a bunch of selftests covering memslots, breakpoints, stage-2 faults and access tracking. You name it, we got it, we probably broke it. - Pick a small set of documentation and spelling fixes, because no good merge window would be complete without those. As a side effect, this tag also drags: - The 'kvmarm-fixes-6.1-3' tag as a dependency to the dirty-ring series - A shared branch with the arm64 tree that repaints all the system registers to match the ARM ARM's naming, and resulting in interesting conflicts

Merge branch kvm-arm64/mte-map-shared into kvmarm-master/next

2022-12-05T14:38:24Z

* kvm-arm64/mte-map-shared: : . : Update the MTE support to allow the VMM to use shared mappings : to back the memslots exposed to MTE-enabled guests. : : Patches courtesy of Catalin Marinas and Peter Collingbourne. : . : Fix a number of issues with MTE, such as races on the tags : being initialised vs the PG_mte_tagged flag as well as the : lack of support for VM_SHARED when KVM is involved. : : Patches from Catalin Marinas and Peter Collingbourne. : . Documentation: document the ABI changes for KVM_CAP_ARM_MTE KVM: arm64: permit all VM_MTE_ALLOWED mappings with MTE enabled KVM: arm64: unify the tests for VMAs in memslots when MTE is enabled arm64: mte: Lock a page for MTE tag initialisation mm: Add PG_arch_3 page flag KVM: arm64: Simplify the sanitise_mte_tags() logic arm64: mte: Fix/clarify the PG_mte_tagged semantics mm: Do not enable PG_arch_2 for all 64-bit architectures Signed-off-by: Marc Zyngier

Merge branch kvm-arm64/pkvm-vcpu-state into kvmarm-master/next

2022-12-05T14:37:23Z

* kvm-arm64/pkvm-vcpu-state: (25 commits) : . : Large drop of pKVM patches from Will Deacon and co, adding : a private vm/vcpu state at EL2, managed independently from : the EL1 state. From the cover letter: : : "This is version six of the pKVM EL2 state series, extending the pKVM : hypervisor code so that it can dynamically instantiate and manage VM : data structures without the host being able to access them directly. : These structures consist of a hyp VM, a set of hyp vCPUs and the stage-2 : page-table for the MMU. The pages used to hold the hypervisor structures : are returned to the host when the VM is destroyed." : . KVM: arm64: Use the pKVM hyp vCPU structure in handle___kvm_vcpu_run() KVM: arm64: Don't unnecessarily map host kernel sections at EL2 KVM: arm64: Explicitly map 'kvm_vgic_global_state' at EL2 KVM: arm64: Maintain a copy of 'kvm_arm_vmid_bits' at EL2 KVM: arm64: Unmap 'kvm_arm_hyp_percpu_base' from the host KVM: arm64: Return guest memory from EL2 via dedicated teardown memcache KVM: arm64: Instantiate guest stage-2 page-tables at EL2 KVM: arm64: Consolidate stage-2 initialisation into a single function KVM: arm64: Add generic hyp_memcache helpers KVM: arm64: Provide I-cache invalidation by virtual address at EL2 KVM: arm64: Initialise hypervisor copies of host symbols unconditionally KVM: arm64: Add per-cpu fixmap infrastructure at EL2 KVM: arm64: Instantiate pKVM hypervisor VM and vCPU structures from EL1 KVM: arm64: Add infrastructure to create and track pKVM instances at EL2 KVM: arm64: Rename 'host_kvm' to 'host_mmu' KVM: arm64: Add hyp_spinlock_t static initializer KVM: arm64: Include asm/kvm_mmu.h in nvhe/mem_protect.h KVM: arm64: Add helpers to pin memory shared with the hypervisor at EL2 KVM: arm64: Prevent the donation of no-map pages KVM: arm64: Implement do_donate() helper for donating memory ... Signed-off-by: Marc Zyngier

Merge branch kvm-arm64/parallel-faults into kvmarm-master/next

2022-12-05T14:22:55Z

* kvm-arm64/parallel-faults: : . : Parallel stage-2 fault handling, courtesy of Oliver Upton. : From the cover letter: : : "Presently KVM only takes a read lock for stage 2 faults if it believes : the fault can be fixed by relaxing permissions on a PTE (write unprotect : for dirty logging). Otherwise, stage 2 faults grab the write lock, which : predictably can pile up all the vCPUs in a sufficiently large VM. : : Like the TDP MMU for x86, this series loosens the locking around : manipulations of the stage 2 page tables to allow parallel faults. RCU : and atomics are exploited to safely build/destroy the stage 2 page : tables in light of multiple software observers." : . KVM: arm64: Reject shared table walks in the hyp code KVM: arm64: Don't acquire RCU read lock for exclusive table walks KVM: arm64: Take a pointer to walker data in kvm_dereference_pteref() KVM: arm64: Handle stage-2 faults in parallel KVM: arm64: Make table->block changes parallel-aware KVM: arm64: Make leaf->leaf PTE changes parallel-aware KVM: arm64: Make block->table PTE changes parallel-aware KVM: arm64: Split init and set for table PTE KVM: arm64: Atomically update stage 2 leaf attributes in parallel walks KVM: arm64: Protect stage-2 traversal with RCU KVM: arm64: Tear down unlinked stage-2 subtree after break-before-make KVM: arm64: Use an opaque type for pteps KVM: arm64: Add a helper to tear down unlinked stage-2 subtrees KVM: arm64: Don't pass kvm_pgtable through kvm_pgtable_walk_data KVM: arm64: Pass mm_ops through the visitor context KVM: arm64: Stash observed pte value in visitor context KVM: arm64: Combine visitor arguments into a context structure Signed-off-by: Marc Zyngier

KVM: arm64: Fix benign bug with incorrect use of VA_BITS

2022-12-05T14:17:53Z

get_user_mapping_size() uses kvm's pgtable library to walk a user space page table created by the kernel, and in doing so, passes metadata that the library needs, including ia_bits, which defines the size of the input address. For the case where the kernel is compiled for 52 VA bits but runs on HW that does not support LVA, it will fall back to 48 VA bits at runtime. Therefore we must use vabits_actual rather than VA_BITS to get the true address size. This is benign in the current code base because the pgtable library only uses it for error checking. Fixes: 6011cf68c885 ("KVM: arm64: Walk userspace page tables to compute the THP mapping size") Signed-off-by: Ryan Roberts Signed-off-by: Marc Zyngier Link: https://lore.kernel.org/r/20221205114031.3972780-1-ryan.roberts@arm.com

KVM: arm64: permit all VM_MTE_ALLOWED mappings with MTE enabled

2022-11-29T09:26:07Z

Certain VMMs such as crosvm have features (e.g. sandboxing) that depend on being able to map guest memory as MAP_SHARED. The current restriction on sharing MAP_SHARED pages with the guest is preventing the use of those features with MTE. Now that the races between tasks concurrently clearing tags on the same page have been fixed, remove this restriction. Note that this is a relaxation of the ABI. Signed-off-by: Peter Collingbourne Reviewed-by: Catalin Marinas Reviewed-by: Steven Price Reviewed-by: Cornelia Huck Signed-off-by: Marc Zyngier Link: https://lore.kernel.org/r/20221104011041.290951-8-pcc@google.com