[PATCH] powerpc/pseries/iommu: memory notifier incorrectly adds TCEs for pmemory
Donet Tom
donettom at linux.ibm.com
Thu Feb 6 17:15:15 AEDT 2025
On 2/5/25 19:28, Gaurav Batra wrote:
>
> On 2/5/25 6:43 AM, Donet Tom wrote:
>>
>> On 1/31/25 00:08, Gaurav Batra wrote:
>>> iommu_mem_notifier() is invoked when RAM is dynamically
>>> added/removed. This
>>> notifier call is responsible to add/remove TCEs from the Dynamic DMA
>>> Window
>>> (DDW) when TCEs are pre-mapped. TCEs are pre-mapped only for RAM and
>>> not
>>> for persistent memory (pmemory). For DMA buffers in pmemory, TCEs are
>>> dynamically mapped when the device driver instructs to do so.
>>>
>>> The issue is 'daxctl' command is capable of adding pmemory as
>>> "System RAM"
>>> after LPAR boot. The command to do so is -
>>>
>>> daxctl reconfigure-device --mode=system-ram dax0.0 --force
>>>
>>> This will dynamically add pmemory range to LPAR RAM eventually invoking
>>> iommu_mem_notifier(). The address range of pmemory is way beyond the
>>> Max
>>> RAM that the LPAR can have. Which means, this range is beyond the DDW
>>> created for the device, at device initialization time.
>>>
>>> As a result when TCEs are pre-mapped for the pmemory range, by
>>> iommu_mem_notifier(), PHYP HCALL returns H_PARAMETER. This failed the
>>> command, daxctl, to add pmemory as RAM.
>>>
>>> The solution is to not pre-map TCEs for pmemory.
>>>
>>> Signed-off-by: Gaurav Batra <gbatra at linux.ibm.com>
>>> ---
>>> arch/powerpc/include/asm/mmzone.h | 1 +
>>> arch/powerpc/mm/numa.c | 2 +-
>>> arch/powerpc/platforms/pseries/iommu.c | 29
>>> ++++++++++++++------------
>>> 3 files changed, 18 insertions(+), 14 deletions(-)
>>>
>>> diff --git a/arch/powerpc/include/asm/mmzone.h
>>> b/arch/powerpc/include/asm/mmzone.h
>>> index d99863cd6cde..049152f8d597 100644
>>> --- a/arch/powerpc/include/asm/mmzone.h
>>> +++ b/arch/powerpc/include/asm/mmzone.h
>>> @@ -29,6 +29,7 @@ extern cpumask_var_t node_to_cpumask_map[];
>>> #ifdef CONFIG_MEMORY_HOTPLUG
>>> extern unsigned long max_pfn;
>>> u64 memory_hotplug_max(void);
>>> +u64 hot_add_drconf_memory_max(void);
>>> #else
>>> #define memory_hotplug_max() memblock_end_of_DRAM()
>>> #endif
>>> diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
>>> index 3c1da08304d0..603a0f652ba6 100644
>>> --- a/arch/powerpc/mm/numa.c
>>> +++ b/arch/powerpc/mm/numa.c
>>> @@ -1336,7 +1336,7 @@ int hot_add_scn_to_nid(unsigned long scn_addr)
>>> return nid;
>>> }
>>> -static u64 hot_add_drconf_memory_max(void)
>>> +u64 hot_add_drconf_memory_max(void)
>>> {
>>> struct device_node *memory = NULL;
>>> struct device_node *dn = NULL;
>>> diff --git a/arch/powerpc/platforms/pseries/iommu.c
>>> b/arch/powerpc/platforms/pseries/iommu.c
>>> index 29f1a0cc59cd..abd9529a8f41 100644
>>> --- a/arch/powerpc/platforms/pseries/iommu.c
>>> +++ b/arch/powerpc/platforms/pseries/iommu.c
>>> @@ -1284,17 +1284,13 @@ static LIST_HEAD(failed_ddw_pdn_list);
>>> static phys_addr_t ddw_memory_hotplug_max(void)
>>> {
>>> - resource_size_t max_addr = memory_hotplug_max();
>>> - struct device_node *memory;
>>> + resource_size_t max_addr;
>>> - for_each_node_by_type(memory, "memory") {
>>> - struct resource res;
>>> -
>>> - if (of_address_to_resource(memory, 0, &res))
>>> - continue;
>>> -
>>> - max_addr = max_t(resource_size_t, max_addr, res.end + 1);
>>> - }
>>> +#if defined(CONFIG_NUMA) && defined(CONFIG_MEMORY_HOTPLUG)
>>> + max_addr = hot_add_drconf_memory_max();
>>> +#else
>>> + max_addr = memblock_end_of_DRAM();
>>> +#endif
>>> return max_addr;
>>> }
>>> @@ -1600,7 +1596,7 @@ static bool enable_ddw(struct pci_dev *dev,
>>> struct device_node *pdn)
>>> if (direct_mapping) {
>>> /* DDW maps the whole partition, so enable direct DMA
>>> mapping */
>>> - ret = walk_system_ram_range(0, memblock_end_of_DRAM() >>
>>> PAGE_SHIFT,
>>> + ret = walk_system_ram_range(0, ddw_memory_hotplug_max() >>
>>> PAGE_SHIFT,
>>> win64->value,
>>> tce_setrange_multi_pSeriesLP_walk);
>>> if (ret) {
>>> dev_info(&dev->dev, "failed to map DMA window for
>>> %pOF: %d\n",
>>> @@ -2346,11 +2342,17 @@ static int iommu_mem_notifier(struct
>>> notifier_block *nb, unsigned long action,
>>> struct memory_notify *arg = data;
>>> int ret = 0;
>>> + /* This notifier can get called when onlining persistent
>>> memory as well.
>>> + * TCEs are not pre-mapped for persistent memory. Persistent
>>> memory will
>>> + * always be above ddw_memory_hotplug_max()
>>> + */
>>> +
>>> switch (action) {
>>> case MEM_GOING_ONLINE:
>>> spin_lock(&dma_win_list_lock);
>>> list_for_each_entry(window, &dma_win_list, list) {
>>> - if (window->direct) {
>>> + if (window->direct && (arg->start_pfn << PAGE_SHIFT) <
>>> + ddw_memory_hotplug_max()) {
>> Hi Gaurav,
>>
>> Since the pmem_start will be greater than ddw_memory_hotplug_max(),
>> and we have not created DDW beyond ddw_memory_hotplug_max(), we are
>> not adding TCE for this range, right?
>>
> That is correct
>
Thank you.
This looks good to me. feel free to add
Tested-by: Donet Tom <donettom at linux.ibm.com>
Reviewed-by: Donet Tom <donettom at linux.ibm.com>
>
>> I have tested this patch on my system, and daxctl reconfigure-device
>> is able to reconfigure PMEM to system RAM.
>>
>> ~# daxctl reconfigure-device --mode=system-ram dax1.0 --force
>> [
>> {
>> "chardev":"dax1.0",
>> "size":5362417664,
>> "target_node":4,
>> "align":65536,
>> "mode":"system-ram",
>> "online_memblocks":4,
>> "total_memblocks":4,
>> "movable":true
>> }
>> ]
>> reconfigured 1 device
>> ~#
>> ~# lsmem
>> RANGE SIZE STATE REMOVABLE BLOCK
>> 0x0000000000000000-0x000000697fffffff 422G online yes 0-421
>> 0x0000040380000000-0x000004047fffffff 4G online yes 4110-4113
>>
>> Memory block size: 1G
>> Total online memory: 426G
>> Total offline memory: 0B
>> root at ltcden14-lp2:~#
>>
>> Thanks
>> Donet
>>> ret |= tce_setrange_multi_pSeriesLP(arg->start_pfn,
>>> arg->nr_pages, window->prop);
>>> }
>>> @@ -2362,7 +2364,8 @@ static int iommu_mem_notifier(struct
>>> notifier_block *nb, unsigned long action,
>>> case MEM_OFFLINE:
>>> spin_lock(&dma_win_list_lock);
>>> list_for_each_entry(window, &dma_win_list, list) {
>>> - if (window->direct) {
>>> + if (window->direct && (arg->start_pfn << PAGE_SHIFT) <
>>> + ddw_memory_hotplug_max()) {
>>> ret |= tce_clearrange_multi_pSeriesLP(arg->start_pfn,
>>> arg->nr_pages, window->prop);
>>> }
>>>
>>> base-commit: 95ec54a420b8f445e04a7ca0ea8deb72c51fe1d3
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