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+id = 1078
+title = "qemu-system-arm: unable to use LPAE"
+state = "closed"
+created_at = "2022-06-16T11:56:50.844Z"
+closed_at = "2022-06-27T22:55:20.002Z"
+labels = ["Closed::Fixed", "target: arm"]
+url = "https://gitlab.com/qemu-project/qemu/-/issues/1078"
+host-os = "Ubuntu 18.04.6 LTS"
+host-arch = "x86_64"
+qemu-version = "QEMU emulator version 7.0.50 (v7.0.0-1865-g9ac873a469-dirty)"
+guest-os = "irrelevant"
+guest-arch = "qemuarm cortex-a15"
+description = """Failed to run qemu: qemu-system-arm: Addressing limited to 32 bits,
+but memory exceeds it by 1073741824 bytes"""
+reproduce = """1. ./configure --target-list=arm-softmmu
+2. make
+3.
+./qemu-system-arm \\
+-machine virt,highmem=on \\
+-cpu cortex-a15 -smp 4 \\
+-m 4096 \\
+-kernel ./zImage \\
+-drive id=disk0,file=./rootfs.ext4,if=none,format=raw \\
+-object rng-random,filename=/dev/urandom,id=rng0 \\
+-device virtio-rng-pci,rng=rng0 \\
+-device virtio-blk-device,drive=disk0 \\
+-device virtio-gpu-pci \\
+-serial mon:stdio -serial null \\
+-nographic \\
+-append 'root=/dev/vda rw mem=4096M ip=dhcp console=ttyAMA0 console=hvc0'"""
+additional = """We set physical address bits to 40 if ARM_FEATURE_LPAE is enabled. But ARM_FEATURE_V7VE also implies ARM_FEATURE_LPAE as set later in arm_cpu_realizefn.
+
+We should add condition for ARM_FEATURE_V7VE, otherwise we would not be able to use highmem larger than 3GB even though we have enabled highmem, since we would fail and return right from machvirt_init. 
+
+I have already made a patch to fix this issue.
+https://gitlab.com/realhezhe/qemu/-/commit/4dad8167c1c1a7695af88d8929e8d7f6399177de
+`hw/arm/virt.c`
+```c
+        if (object_property_get_bool(cpuobj, "aarch64", NULL)) {
+            pa_bits = arm_pamax(armcpu);
+        } else if (arm_feature(&armcpu->env, ARM_FEATURE_LPAE)) {
+        } else if (arm_feature(&armcpu->env, ARM_FEATURE_LPAE)
+                || arm_feature(&armcpu->env, ARM_FEATURE_V7VE)) {
+            /* v7 with LPAE */
+            pa_bits = 40;
+        } else {
+```
+
+After applying the patch, I can make sure that the pa_bits has already been set to 40, but qemu hangs later. By bisecting I found if the following commit is reverted qemu can boot up successfully..
+39a1fd2528 ("target/arm: Fix handling of LPAE block descriptors")
+
+It can't be quickly determined what's going on here at my side. Maybe the author can help give some hints. Thanks."""