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Date: Tue, 23 Jun 2020 11:12:10 +1000
From: Alexey Kardashevskiy <aik@...abs.ru>
To: Leonardo Bras <leobras.c@...il.com>
Cc: Michael Ellerman <mpe@...erman.id.au>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>,
Thiago Jung Bauermann <bauerman@...ux.ibm.com>,
Ram Pai <linuxram@...ibm.com>, linuxppc-dev@...ts.ozlabs.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] powerpc/pseries/iommu: Update call to
ibm,query-pe-dma-windows
On 23/06/2020 04:58, Leonardo Bras wrote:
> Hello Alexey, thank you for the feedback!
>
> On Mon, 2020-06-22 at 20:02 +1000, Alexey Kardashevskiy wrote:
>>
>> On 19/06/2020 15:06, Leonardo Bras wrote:
>>> From LoPAR level 2.8, "ibm,ddw-extensions" index 3 can make the number of
>>> outputs from "ibm,query-pe-dma-windows" go from 5 to 6.
>>>
>>> This change of output size is meant to expand the address size of
>>> largest_available_block PE TCE from 32-bit to 64-bit, which ends up
>>> shifting page_size and migration_capable.
>>>
>>> This ends up requiring the update of
>>> ddw_query_response->largest_available_block from u32 to u64, and manually
>>> assigning the values from the buffer into this struct, according to
>>> output size.
>>>
>>> Signed-off-by: Leonardo Bras <leobras.c@...il.com>
>>> ---
>>> arch/powerpc/platforms/pseries/iommu.c | 57 +++++++++++++++++++++-----
>>> 1 file changed, 46 insertions(+), 11 deletions(-)
>>>
>>> diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
>>> index 6d47b4a3ce39..e5a617738c8b 100644
>>> --- a/arch/powerpc/platforms/pseries/iommu.c
>>> +++ b/arch/powerpc/platforms/pseries/iommu.c
>>> @@ -334,7 +334,7 @@ struct direct_window {
>>> /* Dynamic DMA Window support */
>>> struct ddw_query_response {
>>> u32 windows_available;
>>> - u32 largest_available_block;
>>> + u64 largest_available_block;
>>> u32 page_size;
>>> u32 migration_capable;
>>> };
>>> @@ -869,14 +869,32 @@ static int find_existing_ddw_windows(void)
>>> }
>>> machine_arch_initcall(pseries, find_existing_ddw_windows);
>>>
>>> +/*
>>> + * From LoPAR level 2.8, "ibm,ddw-extensions" index 3 can rule how many output
>>> + * parameters ibm,query-pe-dma-windows will have, ranging from 5 to 6.
>>> + */
>>> +
>>> +static int query_ddw_out_sz(struct device_node *par_dn)
>>
>> Can easily be folded into query_ddw().
>
> Sure, but it will get inlined by the compiler, and I think it reads
> better this way.
> I mean, I understand you have a reason to think it's better to fold it
> in query_ddw(), and I would like to better understand that to improve
> my code in the future.
You have numbers 5 and 6 (the number of parameters) twice in the file,
this is why I brought it up. query_ddw_out_sz() can potentially return
something else than 5 or 6 and you will have to change the callsite(s)
then, since these are not macros, this allows to think there may be more
places with 5 and 6. Dunno. A single function will simplify things imho.
>
>>> +{
>>> + int ret;
>>> + u32 ddw_ext[3];
>>> +
>>> + ret = of_property_read_u32_array(par_dn, "ibm,ddw-extensions",
>>> + &ddw_ext[0], 3);
>>> + if (ret || ddw_ext[0] < 2 || ddw_ext[2] != 1)
>>
>> Oh that PAPR thing again :-/
>>
>> ===
>> The “ibm,ddw-extensions” property value is a list of integers the first
>> integer indicates the number of extensions implemented and subsequent
>> integers, one per extension, provide a value associated with that
>> extension.
>> ===
>>
>> So ddw_ext[0] is length.
>> Listindex==2 is for "reset" says PAPR and
>> Listindex==3 is for this new 64bit "largest_available_block".
>>
>> So I'd expect ddw_ext[2] to have the "reset" token and ddw_ext[3] to
>> have "1" for this new feature but indexes are smaller. I am confused.
>> Either way these "2" and "3" needs to be defined in macros, "0" probably
>> too.
>
> Remember these indexes are not C-like 0-starting indexes, where the
> size would be Listindex==1.
Yeah I can see that is the assumption but out of curiosity - is it
written anywhere? Across PAPR, they index bytes from 1 but bits from 0 :-/
Either way make them macros.
> Basically, in C-like array it's :
> a[0] == size,
> a[1] == reset_token,
> a[2] == new 64bit "largest_available_block"
>
>> Please post 'lsprop "ibm,ddw-extensions"' here. Thanks,
>
> Sure:
> [root@...t pci@...000029004005]# lsprop "ibm,ddw-extensions"
> ibm,dd
> w-extensions
> 00000002 00000056 00000000
Right, good. Thanks,
>
>
>>
>>> + return 5;
>>> + return 6;
>>> +}
>>> +
>>> static int query_ddw(struct pci_dev *dev, const u32 *ddw_avail,
>>> - struct ddw_query_response *query)
>>> + struct ddw_query_response *query,
>>> + struct device_node *par_dn)
>>> {
>>> struct device_node *dn;
>>> struct pci_dn *pdn;
>>> - u32 cfg_addr;
>>> + u32 cfg_addr, query_out[5];
>>> u64 buid;
>>> - int ret;
>>> + int ret, out_sz;
>>>
>>> /*
>>> * Get the config address and phb buid of the PE window.
>>> @@ -888,12 +906,29 @@ static int query_ddw(struct pci_dev *dev, const u32 *ddw_avail,
>>> pdn = PCI_DN(dn);
>>> buid = pdn->phb->buid;
>>> cfg_addr = ((pdn->busno << 16) | (pdn->devfn << 8));
>>> + out_sz = query_ddw_out_sz(par_dn);
>>> +
>>> + ret = rtas_call(ddw_avail[0], 3, out_sz, query_out,
>>> + cfg_addr, BUID_HI(buid), BUID_LO(buid));
>>> + dev_info(&dev->dev, "ibm,query-pe-dma-windows(%x) %x %x %x returned %d\n",
>>> + ddw_avail[0], cfg_addr, BUID_HI(buid), BUID_LO(buid), ret);
>>> +
>>> + switch (out_sz) {
>>> + case 5:
>>> + query->windows_available = query_out[0];
>>> + query->largest_available_block = query_out[1];
>>> + query->page_size = query_out[2];
>>> + query->migration_capable = query_out[3];
>>> + break;
>>> + case 6:
>>> + query->windows_available = query_out[0];
>>> + query->largest_available_block = ((u64)query_out[1] << 32) |
>>> + query_out[2];
>>> + query->page_size = query_out[3];
>>> + query->migration_capable = query_out[4];
>>> + break;
>>> + }
>>>
>>> - ret = rtas_call(ddw_avail[0], 3, 5, (u32 *)query,
>>> - cfg_addr, BUID_HI(buid), BUID_LO(buid));
>>> - dev_info(&dev->dev, "ibm,query-pe-dma-windows(%x) %x %x %x"
>>> - " returned %d\n", ddw_avail[0], cfg_addr, BUID_HI(buid),
>>> - BUID_LO(buid), ret);
>>> return ret;
>>> }
>>>
>>> @@ -1040,7 +1075,7 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
>>> * of page sizes: supported and supported for migrate-dma.
>>> */
>>> dn = pci_device_to_OF_node(dev);
>>> - ret = query_ddw(dev, ddw_avail, &query);
>>> + ret = query_ddw(dev, ddw_avail, &query, pdn);
>>> if (ret != 0)
>>> goto out_failed;
>>>
>>> @@ -1068,7 +1103,7 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
>>> /* check largest block * page size > max memory hotplug addr */
>>> max_addr = ddw_memory_hotplug_max();
>>> if (query.largest_available_block < (max_addr >> page_shift)) {
>>> - dev_dbg(&dev->dev, "can't map partition max 0x%llx with %u "
>>> + dev_dbg(&dev->dev, "can't map partition max 0x%llx with %llu "
>>> "%llu-sized pages\n", max_addr, query.largest_available_block,
>>> 1ULL << page_shift);
>>> goto out_failed;
>>>
>
> Best regards,
> Leonardo
>
--
Alexey
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