How can I use the 'no-map' property of reserved-memory in device tree? Still accessed with virtual address - memory-management

Question

I have this device tree.
reserved-memory {
#address-cells = <2>;
#size-cells = <2>;
ranges;
axpu_reserved_mem: axpursvd#90000000 {
no-map;
reg = <0x0 0x90000000 0x0 0x30000000>;
};
};
axpu#50000000 {
compatible = "ab21-axpu";
reg = <0 0x50000000 0 0x10000000>;
...
memory-region = <&axpu_reserved_mem>;
};
With simple test, in the probe function, I did something like this (reduced).
struct axpu_dev {
struct device *dev;
void __iomem *base;
u64 paddr;
u64 vaddr;
};
static int axpu_probe(struct platform_device *pdev)
{
struct device *dev = &pdev->dev;
struct resource *res;
struct axpu_dev *axpu;
struct device_node *np;
int rc;
int ret;
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
axpu = devm_kzalloc(dev, sizeof(*axpu), GFP_KERNEL);
axpu->dev = dev;
axpu->base = devm_ioremap(dev, res->start, resource_size(res));
res = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
devm_request_irq(dev, res->start, axpu_irq_handler, IRQF_TRIGGER_HIGH, "axpu_irq", axpu);
np = of_parse_phandle(dev->of_node, "memory-region", 0);
rc = of_address_to_resource(np, 0, res);
axpu->paddr = res->start;
axpu->vaddr = memremap(res->start, resource_size(res), MEMREMAP_WB);
platform_set_drvdata(pdev, axpu);
axpu_init(axpu);
return sysfs_create_group(&dev->kobj, &axpu_attr_group);
}
and in the axpu_init function, I access it with virtual address.
static void axpu_init(struct axpu_dev *axpu)
{
printk("testing reserved memory ..\n");
writel_relaxed(0x12345678, axpu->vaddr + 0);
writel_relaxed(0x23456789, axpu->vaddr + 8);
printk("read-back data = %llx, %llx\n", readl_relaxed(axpu->vaddr + 0), readl_relaxed(axpu->vaddr + 8));
}
When I execute it, it runs ok.
/ # insmod axpu.ko
axpu_probe called!
MEM : res->start = 50000000, res->end = 5fffffff, res->name = axpu#50000000
axpu->base = ffffffc010000000
IRQ : res->start = 15, res->end = 15, res->name = axpu#50000000
axpu_dev 50000000.axpu: Allocated reserved memory, vaddr: 0xFFFFFFC080000000, paddr: 0x90000000
writing 0x12345678 at non-mapped reserved memory 0x90000000, 0x90000008 ..
read-back data = 12345678, 23456789
I have put no-map in the reserved memory sub-node. But is accessible with virtual address.
But if I try it with physical address, it crashes as below.
------------[ cut here ]------------
Ignoring spurious kernel translation fault at virtual address 0000000090000000
WARNING: CPU: 0 PID: 27 at arch/arm64/mm/fault.c:311 __do_kernel_fault+0x108/0x150
odules linked in: axpu(+)
CPU: 0 PID: 27 Comm: insmod Not tainted 5.10.0-rc5 #548
Hardware name: ETRI ab21m (DT)
pstate: 60400009 (nZCv daif +PAN -UAO -TCO BTYPE=--)
pc : __do_kernel_fault+0x108/0x150
lr : __do_kernel_fault+0x108/0x150
The document says about no-map :
no-map (optional) - empty property
- Indicates the operating system must not create a virtual mapping
of the region as part of its standard mapping of system memory,
nor permit speculative access to it under any circumstances other
than under the control of the device driver using the region.
Then what is wrong with my device tree?