On 7/21/20 7:15 AM, Michael Ellerman wrote:
Nathan Lynch <nath...@linux.ibm.com> writes:
"Aneesh Kumar K.V" <aneesh.ku...@linux.ibm.com> writes:
This is the next version of the fixes for memory unplug on radix.
The issues and the fix are described in the actual patches.
I guess this isn't actually causing problems at runtime right now, but I
notice calls to resize_hpt_for_hotplug() from arch_add_memory() and
arch_remove_memory(), which ought to be mmu-agnostic:
int __ref arch_add_memory(int nid, u64 start, u64 size,
struct mhp_params *params)
{
unsigned long start_pfn = start >> PAGE_SHIFT;
unsigned long nr_pages = size >> PAGE_SHIFT;
int rc;
resize_hpt_for_hotplug(memblock_phys_mem_size());
start = (unsigned long)__va(start);
rc = create_section_mapping(start, start + size, nid,
params->pgprot);
...
Hmm well spotted.
That does return early if the ops are not setup:
int resize_hpt_for_hotplug(unsigned long new_mem_size)
{
unsigned target_hpt_shift;
if (!mmu_hash_ops.resize_hpt)
return 0;
And:
void __init hpte_init_pseries(void)
{
...
if (firmware_has_feature(FW_FEATURE_HPT_RESIZE))
mmu_hash_ops.resize_hpt = pseries_lpar_resize_hpt;
And that comes in via ibm,hypertas-functions:
{FW_FEATURE_HPT_RESIZE, "hcall-hpt-resize"},
But firmware is not necessarily going to add/remove that call based on
whether we're using hash/radix.
We are good there because hpte_init_pseries is only called for hash
translation.
early_init_mmu()
-> hash__early_init_mmu
-> hpte_init_pseries
-> mmu_hash_ops.resize_hpt = pseries_lpar_resize_hpt;
So I think a follow-up patch is needed to make this more robust.
Aneesh/Bharata what platform did you test this series on? I'm curious
how this didn't break.
All the changes are tested with kvm.
-aneesh
