Revert "KVM: arm64: Reschedule as needed when destroying the stage-2 page-tables"

This reverts commit e9abe31.

syzkaller has managed to tease out multiple bugs in this change and
fixing-forward didn't remedy the situation. Considering newly-introduced
memory safety issues the potential for scheduler stalls don't seem that
bad in comparison

Link: https://lore.kernel.org/kvmarm/[email protected]/
Message-ID: <[email protected]>
Signed-off-by: Oliver Upton <[email protected]>

Author: oupton

arch/arm64/kvm/mmu.c

@@ -904,35 +904,11 @@ static int kvm_init_ipa_range(struct kvm_s2_mmu *mmu, unsigned long type)
 	return 0;
 }
 
-/*
- * Assume that @pgt is valid and unlinked from the KVM MMU to free the
- * page-table without taking the kvm_mmu_lock and without performing any
- * TLB invalidations.
- *
- * Also, the range of addresses can be large enough to cause need_resched
- * warnings, for instance on CONFIG_PREEMPT_NONE kernels. Hence, invoke
- * cond_resched() periodically to prevent hogging the CPU for a long time
- * and schedule something else, if required.
- */
-static void stage2_destroy_range(struct kvm_pgtable *pgt, phys_addr_t addr,
-				   phys_addr_t end)
-{
-	u64 next;
-
-	do {
-		next = stage2_range_addr_end(addr, end);
-		KVM_PGT_FN(kvm_pgtable_stage2_destroy_range)(pgt, addr,
-								next - addr);
-		if (next != end)
-			cond_resched();
-	} while (addr = next, addr != end);
-}
-
 static void kvm_stage2_destroy(struct kvm_pgtable *pgt)
 {
 	unsigned int ia_bits = VTCR_EL2_IPA(pgt->mmu->vtcr);
 
-	stage2_destroy_range(pgt, 0, BIT(ia_bits));
+	KVM_PGT_FN(kvm_pgtable_stage2_destroy_range)(pgt, 0, BIT(ia_bits));
 	KVM_PGT_FN(kvm_pgtable_stage2_destroy_pgd)(pgt);
 }