• Oliver Upton's avatar
    KVM: arm64: Limit stage2_apply_range() batch size to largest block · 5994bc9e
    Oliver Upton authored
    Presently stage2_apply_range() works on a batch of memory addressed by a
    stage 2 root table entry for the VM. Depending on the IPA limit of the
    VM and PAGE_SIZE of the host, this could address a massive range of
    memory. Some examples:
    
      4 level, 4K paging -> 512 GB batch size
    
      3 level, 64K paging -> 4TB batch size
    
    Unsurprisingly, working on such a large range of memory can lead to soft
    lockups. When running dirty_log_perf_test:
    
      ./dirty_log_perf_test -m -2 -s anonymous_thp -b 4G -v 48
    
      watchdog: BUG: soft lockup - CPU#0 stuck for 45s! [dirty_log_perf_:16703]
      Modules linked in: vfat fat cdc_ether usbnet mii xhci_pci xhci_hcd sha3_generic gq(O)
      CPU: 0 PID: 16703 Comm: dirty_log_perf_ Tainted: G           O       6.0.0-smp-DEV #1
      pstate: 80400009 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
      pc : dcache_clean_inval_poc+0x24/0x38
      lr : clean_dcache_guest_page+0x28/0x4c
      sp : ffff800021763990
      pmr_save: 000000e0
      x29: ffff800021763990 x28: 0000000000000005 x27: 0000000000000de0
      x26: 0000000000000001 x25: 00400830b13bc77f x24: ffffad4f91ead9c0
      x23: 0000000000000000 x22: ffff8000082ad9c8 x21: 0000fffafa7bc000
      x20: ffffad4f9066ce50 x19: 0000000000000003 x18: ffffad4f92402000
      x17: 000000000000011b x16: 000000000000011b x15: 0000000000000124
      x14: ffff07ff8301d280 x13: 0000000000000000 x12: 00000000ffffffff
      x11: 0000000000010001 x10: fffffc0000000000 x9 : ffffad4f9069e580
      x8 : 000000000000000c x7 : 0000000000000000 x6 : 000000000000003f
      x5 : ffff07ffa2076980 x4 : 0000000000000001 x3 : 000000000000003f
      x2 : 0000000000000040 x1 : ffff0830313bd000 x0 : ffff0830313bcc40
      Call trace:
       dcache_clean_inval_poc+0x24/0x38
       stage2_unmap_walker+0x138/0x1ec
       __kvm_pgtable_walk+0x130/0x1d4
       __kvm_pgtable_walk+0x170/0x1d4
       __kvm_pgtable_walk+0x170/0x1d4
       __kvm_pgtable_walk+0x170/0x1d4
       kvm_pgtable_stage2_unmap+0xc4/0xf8
       kvm_arch_flush_shadow_memslot+0xa4/0x10c
       kvm_set_memslot+0xb8/0x454
       __kvm_set_memory_region+0x194/0x244
       kvm_vm_ioctl_set_memory_region+0x58/0x7c
       kvm_vm_ioctl+0x49c/0x560
       __arm64_sys_ioctl+0x9c/0xd4
       invoke_syscall+0x4c/0x124
       el0_svc_common+0xc8/0x194
       do_el0_svc+0x38/0xc0
       el0_svc+0x2c/0xa4
       el0t_64_sync_handler+0x84/0xf0
       el0t_64_sync+0x1a0/0x1a4
    
    Use the largest supported block mapping for the configured page size as
    the batch granularity. In so doing the walker is guaranteed to visit a
    leaf only once.
    Signed-off-by: default avatarOliver Upton <oliver.upton@linux.dev>
    Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
    Link: https://lore.kernel.org/r/20221007234151.461779-3-oliver.upton@linux.dev
    5994bc9e
mmu.c 48.6 KB