This series adds support for using the Arm Memory Tagging Extensions (MTE) in a KVM guest.
Changes since v11[1]: * Series is prefixed with a bug fix for a potential race synchronising tags. This is basically race as was recently[2] fixed for PG_dcache_clean where the update of the page flag cannot be done atomically with the work that flag represents. For the PG_dcache_clean case the problem is easier because extra cache maintenance isn't a problem, but here restoring the tags twice could cause data loss. The current solution is a global spinlock for mte_sync_page_tags(). If we hit scalability problems that other solutions such as potentially using another page flag as a lock will need to be investigated. * The second patch is from Catalin to mitigate the performance impact of the first - by handling the page zeroing case explicitly we can avoid entering mte_sync_page_tags() at all in most cases. Peter Collingbourne has a patch which similarly improves this case using the DC GZVA instruction. So this patch may be dropped in favour of Peter's, however Catalin's is likely easier to backport. * Use pte_access_permitted() in set_pte_at() to identify pages which may be accessed by the user rather than open-coding a check for PTE_USER. Also add a comment documenting what's going on. There's also some short-cuts added in mte_sync_tags() compared to the previous post, to again mitigate the performance impact of the first patch. * Move the code to sanitise tags out of user_mem_abort() into its own function. Also call this new function from kvm_set_spte_gfn() as that path was missing the sanitising. Originally I was going to move the code all the way down to kvm_pgtable_stage2_map(). Sadly as that also part of the EL2 hypervisor this breaks nVHE as the code needs to perform actions in the host. * Drop the union in struct kvm_vcpu_events - it served no purpose and was confusing. * Update CAP number (again) and other minor conflict resolutions. [1] https://lore.kernel.org/r/20210416154309.22129-1-steven.pr...@arm.com/ [2] https://lore.kernel.org/r/20210514095001.13236-1-catalin.mari...@arm.com/ [3] https://lore.kernel.org/r/de812a02fd94a0dba07d43606bd893c564aa4528.1620849613.git....@google.com/ Catalin Marinas (1): arm64: Handle MTE tags zeroing in __alloc_zeroed_user_highpage() Steven Price (7): arm64: mte: Handle race when synchronising tags arm64: mte: Sync tags for pages where PTE is untagged arm64: kvm: Introduce MTE VM feature arm64: kvm: Save/restore MTE registers arm64: kvm: Expose KVM_ARM_CAP_MTE KVM: arm64: ioctl to fetch/store tags in a guest KVM: arm64: Document MTE capability and ioctl Documentation/virt/kvm/api.rst | 53 +++++++++++++++ arch/arm64/include/asm/kvm_emulate.h | 3 + arch/arm64/include/asm/kvm_host.h | 9 +++ arch/arm64/include/asm/kvm_mte.h | 66 ++++++++++++++++++ arch/arm64/include/asm/page.h | 6 +- arch/arm64/include/asm/pgtable.h | 9 ++- arch/arm64/include/asm/sysreg.h | 3 +- arch/arm64/include/uapi/asm/kvm.h | 11 +++ arch/arm64/kernel/asm-offsets.c | 3 + arch/arm64/kernel/mte.c | 37 ++++++++-- arch/arm64/kvm/arm.c | 78 ++++++++++++++++++++++ arch/arm64/kvm/hyp/entry.S | 7 ++ arch/arm64/kvm/hyp/exception.c | 3 +- arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 21 ++++++ arch/arm64/kvm/mmu.c | 37 +++++++++- arch/arm64/kvm/sys_regs.c | 28 ++++++-- arch/arm64/mm/fault.c | 21 ++++++ include/uapi/linux/kvm.h | 2 + 18 files changed, 381 insertions(+), 16 deletions(-) create mode 100644 arch/arm64/include/asm/kvm_mte.h -- 2.20.1
