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Date: Wed, 14 Jul 2021 18:38:41 +1000
From: Alexey Kardashevskiy <aik@...abs.ru>
To: Leonardo Brás <leobras.c@...il.com>,
Michael Ellerman <mpe@...erman.id.au>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>,
Joel Stanley <joel@....id.au>,
Christophe Leroy <christophe.leroy@....fr>,
Nicolin Chen <nicoleotsuka@...il.com>,
Niklas Schnelle <schnelle@...ux.ibm.com>
Cc: linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 10/11] powerpc/pseries/iommu: Make use of DDW for
indirect mapping
On 13/07/2021 14:36, Leonardo Brás wrote:
> On Tue, 2021-05-11 at 17:57 +1000, Alexey Kardashevskiy wrote:
>>
>>
>> On 01/05/2021 02:31, Leonardo Bras wrote:
>>> [...]
>>> pmem_present = dn != NULL;
>>> @@ -1218,8 +1224,12 @@ static bool enable_ddw(struct pci_dev *dev,
>>> struct device_node *pdn)
>>>
>>> mutex_lock(&direct_window_init_mutex);
>>>
>>> - if (find_existing_ddw(pdn, &dev->dev.archdata.dma_offset,
>>> &len))
>>> - goto out_unlock;
>>> + if (find_existing_ddw(pdn, &dev->dev.archdata.dma_offset,
>>> &len)) {
>>> + direct_mapping = (len >= max_ram_len);
>>> +
>>> + mutex_unlock(&direct_window_init_mutex);
>>> + return direct_mapping;
>>
>> Does not this break the existing case when direct_mapping==true by
>> skipping setting dev->dev.bus_dma_limit before returning?
>>
>
> Yes, it does. Good catch!
> I changed it to use a flag instead of win64 for return, and now I can
> use the same success exit path for both the new config and the config
> found in list. (out_unlock)
>
>>
>>
>>> + }
>>>
>>> /*
>>> * If we already went through this for a previous function of
>>> @@ -1298,7 +1308,6 @@ static bool enable_ddw(struct pci_dev *dev,
>>> struct device_node *pdn)
>>> goto out_failed;
>>> }
>>> /* verify the window * number of ptes will map the partition
>>> */
>>> - /* check largest block * page size > max memory hotplug addr
>>> */
>>> /*
>>> * The "ibm,pmemory" can appear anywhere in the address
>>> space.
>>> * Assuming it is still backed by page structs, try
>>> MAX_PHYSMEM_BITS
>>> @@ -1320,6 +1329,17 @@ static bool enable_ddw(struct pci_dev *dev,
>>> struct device_node *pdn)
>>> 1ULL << len,
>>> query.largest_available_block,
>>> 1ULL << page_shift);
>>> +
>>> + len = order_base_2(query.largest_available_block <<
>>> page_shift);
>>> + win_name = DMA64_PROPNAME;
>>
>> [1] ....
>>
>>
>>> + } else {
>>> + direct_mapping = true;
>>> + win_name = DIRECT64_PROPNAME;
>>> + }
>>> +
>>> + /* DDW + IOMMU on single window may fail if there is any
>>> allocation */
>>> + if (default_win_removed && !direct_mapping &&
>>> iommu_table_in_use(tbl)) {
>>> + dev_dbg(&dev->dev, "current IOMMU table in use, can't
>>> be replaced.\n");
>>
>>
>> ... remove !direct_mapping and move to [1]?
>
>
> sure, done!
>
>>
>>
>>> goto out_failed;
>>> }
>>>
>>> @@ -1331,8 +1351,7 @@ static bool enable_ddw(struct pci_dev *dev,
>>> struct device_node *pdn)
>>> create.liobn, dn);
>>>
>>> win_addr = ((u64)create.addr_hi << 32) | create.addr_lo;
>>> - win64 = ddw_property_create(DIRECT64_PROPNAME, create.liobn,
>>> win_addr,
>>> - page_shift, len);
>>> + win64 = ddw_property_create(win_name, create.liobn, win_addr,
>>> page_shift, len);
>>> if (!win64) {
>>> dev_info(&dev->dev,
>>> "couldn't allocate property, property name,
>>> or value\n");
>>> @@ -1350,12 +1369,47 @@ static bool enable_ddw(struct pci_dev *dev,
>>> struct device_node *pdn)
>>> if (!window)
>>> goto out_del_prop;
>>>
>>> - ret = walk_system_ram_range(0, memblock_end_of_DRAM() >>
>>> PAGE_SHIFT,
>>> - win64->value,
>>> tce_setrange_multi_pSeriesLP_walk);
>>> - if (ret) {
>>> - dev_info(&dev->dev, "failed to map direct window for
>>> %pOF: %d\n",
>>> - dn, ret);
>>> - goto out_del_list;
>>> + 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,
>>> + win64->value,
>>> tce_setrange_multi_pSeriesLP_walk);
>>> + if (ret) {
>>> + dev_info(&dev->dev, "failed to map direct
>>> window for %pOF: %d\n",
>>> + dn, ret);
>>> + goto out_del_list;
>>> + }
>>> + } else {
>>> + struct iommu_table *newtbl;
>>> + int i;
>>> +
>>> + /* New table for using DDW instead of the default DMA
>>> window */
>>> + newtbl = iommu_pseries_alloc_table(pci->phb->node);
>>> + if (!newtbl) {
>>> + dev_dbg(&dev->dev, "couldn't create new IOMMU
>>> table\n");
>>> + goto out_del_list;
>>> + }
>>> +
>>> + for (i = 0; i < ARRAY_SIZE(pci->phb->mem_resources);
>>> i++) {
>>> + const unsigned long mask = IORESOURCE_MEM_64
>>> | IORESOURCE_MEM;
>>> +
>>> + /* Look for MMIO32 */
>>> + if ((pci->phb->mem_resources[i].flags & mask)
>>> == IORESOURCE_MEM)
>>> + break;
>>
>> What if there is no IORESOURCE_MEM? pci->phb->mem_resources[i].start
>> below will have garbage.
>
>
>
> Yeah, that makes sense. I will add this lines after 'for':
>
> if (i == ARRAY_SIZE(pci->phb->mem_resources)) {
> iommu_tce_table_put(newtbl);
> goto out_del_list;
> }
>
> What do you think?
Move this and that "for" before iommu_pseries_alloc_table() so you won't
need to free if there is no IORESOURCE_MEM.
>
>
>>
>>
>>> + }
>>> +
>>> + _iommu_table_setparms(newtbl, pci->phb->bus->number,
>>> create.liobn, win_addr,
>>> + 1UL << len, page_shift, 0,
>>> &iommu_table_lpar_multi_ops);
>>> + iommu_init_table(newtbl, pci->phb->node, pci->phb-
>>>> mem_resources[i].start,
>>> + pci->phb->mem_resources[i].end);
>>> +
>>> + if (default_win_removed)
>>> + iommu_tce_table_put(tbl);
>>
>>
>> iommu_tce_table_put() should have been called when the window was
>> removed.
>>
>> Also after some thinking - what happens if there were 2 devices in the
>> PE and one requested 64bit DMA? This will only update
>> set_iommu_table_base() for the 64bit one but not for the other.
>>
>> I think the right thing to do is:
>>
>> 1. check if table[0] is in use, if yes => fail (which this does
>> already)
>>
>> 2. remove default dma window but keep the iommu_table struct with one
>> change - set it_size to 0 (and free it_map) so the 32bit device won't
>> look at a stale structure and think there is some window (imaginery
>> situation for phyp but easy to recreate in qemu).
>>
>> 3. use table[1] for newly created indirect DDW window.
>>
>> 4. change get_iommu_table_base() to return a usable table (or may be
>> not
>> needed?).
>>
>> If this sounds reasonable (does it?),
>
> Looks ok, I will try your suggestion.
> I was not aware of how pci->table_group->tables[] worked, so I replaced
> pci->table_group->tables[0] with the new tbl, while moving the older in
> pci->table_group->tables[1].
pci->table_group->tables[0] is window#0 at @0.
pci->table_group->tables[1] is window#1 at 0x0800.0000.0000.0000. That
is all :)
pseries does not use tables[1] but powernv does (by VFIO only though).
> (4) get_iommu_table_base() does not seem to need update, as it returns
> the tlb set by set_iommu_table_base() which is already called in the
> !direct_mapping path in current patch.
Sounds right.
>
>> the question is now if you have
>> time to do that and the hardware to test that, or I'll have to finish
>> the work :)
>
> Sorry, for some reason part of this got lost in Evolution mail client.
>
> If possible, I do want to finish this work, and I am talking to IBM
> Virt people in order to get testing HW.
Even I struggle to find a powervm machine :)
>>
>>
>>> + else
>>> + pci->table_group->tables[1] = tbl;
>>
>>
>> What is this for?
>
> I was thinking of adding the older table to pci->table_group->tables[1]
> while keeping the newer table on pci->table_group->tables[0].
> This did work, but I think your suggestion may work better.
>
> Best regards,
> Leonardo Bras
>
>
--
Alexey
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