[Question] mm/resource: a mistake to use IORESOURCE_SYSRAM instead of IORESOURCE_SYSTEM_RAM?
From: Eric Ren <hidden>
Date: 2021-12-21 10:14:34
Hi David, I feel confused on this piece of code:
void release_mem_region_adjustable(resource_size_t start,
resource_size_t size)
{
... snip
/*
* All memory regions added from memory-hotplug path have the
* flag IORESOURCE_SYSTEM_RAM. If the resource does not have
* this flag, we know that we are dealing with a resource coming
* from HMM/devm. HMM/devm use another mechanism to add/release
* a resource. This goes via devm_request_mem_region and
* devm_release_mem_region.
* HMM/devm take care to release their resources when they want,
* so if we are dealing with them, let us just back off here.
*/
if (!(res->flags & IORESOURCE_SYSRAM)) {
break;
}
The comment says IORESOURCE_SYSTEM_RAM while IORESOURCE_SYSRAM is actually used. Is this a mistake? The reason why I come to read about this is that, I got -EEXIST error from add_memory_driver_managed() when I want to virtio_mem regions sitting on Reserved memory region like this in /proc/iomem:
fffc0000-183fffffff : Reserved
100000000-183fffffff : System RAM (virtio_mem)
1820000000-183fffffff : System RAM (virtio_mem) // --> plugged MB
EEXIST error happens after plug -> unplug -> plug testing, because the hot-added region remains after unplug. The hot-added region is under Reserved region. The IORESOURCE_SYSRAM flag check will skips to handle children of the Reserved region. Thanks in advance! Eric