KVM: arm64: Limit stage2_apply_range() batch size to largest block

Bugzilla: https://bugzilla.redhat.com/2128973

commit 5994bc9
Author: Oliver Upton <oliver.upton@linux.dev>
Date:   Fri Oct 7 23:41:51 2022 +0000

    KVM: arm64: Limit stage2_apply_range() batch size to largest block

    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 ctrliq#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: Oliver Upton <oliver.upton@linux.dev>
    Signed-off-by: Marc Zyngier <maz@kernel.org>
    Link: https://lore.kernel.org/r/20221007234151.461779-3-oliver.upton@linux.dev

Signed-off-by: Cornelia Huck <cohuck@redhat.com>

Author: cohuck

arch/arm64/include/asm/stage2_pgtable.h

@@ -10,13 +10,6 @@
 
 #include <linux/pgtable.h>
 
-/*
- * PGDIR_SHIFT determines the size a top-level page table entry can map
- * and depends on the number of levels in the page table. Compute the
- * PGDIR_SHIFT for a given number of levels.
- */
-#define pt_levels_pgdir_shift(lvls)	ARM64_HW_PGTABLE_LEVEL_SHIFT(4 - (lvls))
-
 /*
  * The hardware supports concatenation of up to 16 tables at stage2 entry
  * level and we use the feature whenever possible, which means we resolve 4
@@ -30,24 +23,11 @@
 #define stage2_pgtable_levels(ipa)	ARM64_HW_PGTABLE_LEVELS((ipa) - 4)
 #define kvm_stage2_levels(kvm)		VTCR_EL2_LVLS(kvm->arch.vtcr)
 
-/* stage2_pgdir_shift() is the size mapped by top-level stage2 entry for the VM */
-#define stage2_pgdir_shift(kvm)		pt_levels_pgdir_shift(kvm_stage2_levels(kvm))
-#define stage2_pgdir_size(kvm)		(1ULL << stage2_pgdir_shift(kvm))
-#define stage2_pgdir_mask(kvm)		~(stage2_pgdir_size(kvm) - 1)
-
 /*
  * kvm_mmmu_cache_min_pages() is the number of pages required to install
  * a stage-2 translation. We pre-allocate the entry level page table at
  * the VM creation.
  */
 #define kvm_mmu_cache_min_pages(kvm)	(kvm_stage2_levels(kvm) - 1)
 
-static inline phys_addr_t
-stage2_pgd_addr_end(struct kvm *kvm, phys_addr_t addr, phys_addr_t end)
-{
-	phys_addr_t boundary = (addr + stage2_pgdir_size(kvm)) & stage2_pgdir_mask(kvm);
-
-	return (boundary - 1 < end - 1) ? boundary : end;
-}
-
 #endif	/* __ARM64_S2_PGTABLE_H_ */

arch/arm64/kvm/mmu.c

@@ -31,6 +31,13 @@ static phys_addr_t hyp_idmap_vector;
 
 static unsigned long io_map_base;
 
+static phys_addr_t stage2_range_addr_end(phys_addr_t addr, phys_addr_t end)
+{
+	phys_addr_t size = kvm_granule_size(KVM_PGTABLE_MIN_BLOCK_LEVEL);
+	phys_addr_t boundary = ALIGN_DOWN(addr + size, size);
+
+	return (boundary - 1 < end - 1) ? boundary : end;
+}
 
 /*
  * Release kvm_mmu_lock periodically if the memory region is large. Otherwise,
@@ -52,7 +59,7 @@ static int stage2_apply_range(struct kvm *kvm, phys_addr_t addr,
 		if (!pgt)
 			return -EINVAL;
 
-		next = stage2_pgd_addr_end(kvm, addr, end);
+		next = stage2_range_addr_end(addr, end);
 		ret = fn(pgt, addr, next - addr);
 		if (ret)
 			break;