Re: PCIE Memory Information

[Aditya Gupta <adityag@linux.ibm.com>]

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Hi Ashraf,

On 04/05/24 12:45, Muzammil Ashraf wrote:
> Hi All,
>
> I am debugging a PCI subsystem. I saw callbacks registered here to
> catch the pcie config read/write request at hw/pci/pci_host.c:201. How
> can I make my subregion to overlap this area and How to receive those
> pcie config read/write requests to my callbacks?
>
Can go through this doc: 
https://www.qemu.org/docs/master/devel/memory.html#overlapping-regions-and-priority

Normally the callbacks you mentioned will be registered on a 
MemoryRegion. You can create your own MemoryRegion, and set your custom 
.read, .write callbacks.

And setting the MemoryRegion's priority as a big positive number.


FWIW, had did something like this in past:


+static uint64_t adi_region_read(void *chip10, hwaddr addr, unsigned size) {
+ // your code
+}
+
+static void adi_region_write(void *chip10, hwaddr addr, uint64_t value, 
unsigned size) {
+ // your code
+}
+
+static const MemoryRegionOps adi_region_ops = {
+    .read = adi_region_read,
+    .write = adi_region_write,
+        .endianness = DEVICE_BIG_ENDIAN,
+    .impl = {
+        .min_access_size = 4,
+        .max_access_size = 4,
+    },
+};
+

+    static hwaddr ADI_REGION_BASE = 0x0006010000000000ull + 0x100;
+

+    memory_region_init_io(&chip10->adi_region, OBJECT(chip10), 
&adi_region_ops, chip10, "custom region: adityag", 0x100);
+    memory_region_add_subregion(get_system_memory(), ADI_REGION_BASE, 
&chip10->adi_region);

Instead of 'get_system_memory', you will have to see what is the PCI 
config region a subregion of.


Then, set the MemoryRegion's priority to some big number.

Then, you can verify if your overlapping was successful, with something 
like this:


+    MemoryRegion *mr = address_space_translate(&address_space_memory, 
ADI_REGION_BASE, &xlat, &l, false, MEMTXATTRS_UNSPECIFIED);

or

+    cpu_physical_memory_read(ADI_REGION_BASE, &val, 4);


1st should return your MemoryRegion, and second one should call your 
.read callback.


Thanks,

Aditya Gupta

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