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From: Alexey Kardashevskiy <aik@ozlabs.ru>
To: "Leonardo Brás" <leobras.c@gmail.com>,
"Frederic Barrat" <fbarrat@linux.ibm.com>,
"Michael Ellerman" <mpe@ellerman.id.au>,
"Benjamin Herrenschmidt" <benh@kernel.crashing.org>,
"Paul Mackerras" <paulus@samba.org>,
"David Gibson" <david@gibson.dropbear.id.au>,
"kernel test robot" <lkp@intel.com>,
"Nicolin Chen" <nicoleotsuka@gmail.com>
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 02/11] powerpc/kernel/iommu: Add new iommu_table_in_use() helper
Date: Tue, 20 Jul 2021 19:41:02 +1000 [thread overview]
Message-ID: <cd309d68-65ac-0ce9-c941-520ac6402f8e@ozlabs.ru> (raw)
In-Reply-To: <283e44591010dcb0690769afaef147add3b36978.camel@gmail.com>
On 20/07/2021 15:38, Leonardo Brás wrote:
> Hello Fred, thanks for this feedback!
>
> Sorry if I miss anything, this snippet was written for v1 over an year
> ago, and I have not taken a look at it ever since.
>
> On Mon, 2021-07-19 at 15:53 +0200, Frederic Barrat wrote:
>>
>>
>> On 16/07/2021 10:27, Leonardo Bras wrote:
>>> @@ -1099,18 +1105,13 @@ int iommu_take_ownership(struct iommu_table
>>> *tbl)
>>> for (i = 0; i < tbl->nr_pools; i++)
>>> spin_lock_nest_lock(&tbl->pools[i].lock, &tbl-
>>>> large_pool.lock);
>>>
>>> - iommu_table_release_pages(tbl);
>>> -
>>> - if (!bitmap_empty(tbl->it_map, tbl->it_size)) {
>>> + if (iommu_table_in_use(tbl)) {
>>> pr_err("iommu_tce: it_map is not empty");
>>> ret = -EBUSY;
>>> - /* Undo iommu_table_release_pages, i.e. restore
>>> bit#0, etc */
>>> - iommu_table_reserve_pages(tbl, tbl-
>>>> it_reserved_start,
>>> - tbl->it_reserved_end);
>>> - } else {
>>> - memset(tbl->it_map, 0xff, sz);
>>> }
>>>
>>> + memset(tbl->it_map, 0xff, sz);
>>> +
>>
>>
>> So if the table is not empty, we fail (EBUSY) but we now also
>> completely
>> overwrite the bitmap. It was in an unexpected state, but we're making
>> it
>> worse. Or am I missing something?
>
> IIRC there was a reason to do that at the time, but TBH I don't really
> remember it, and by looking at the code right now you seem to be
> correct about this causing trouble.
>
> I will send a v6 fixing it soon.
> Please review the remaining patches for some issue I may be missing.
>
> Alexey, any comments on that?
Agree with Fred, this is a bug, EBUSY is not that unexpected :-/ Thanks,
>
>>
>> Fred
>>
>
> Again, thank you for reviewing Fred!
> Best regards,
> Leonardo Bras
>
>
>
>
>
--
Alexey
next prev parent reply other threads:[~2021-07-20 9:42 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-16 8:27 [PATCH v5 00/11] DDW + Indirect Mapping Leonardo Bras
2021-07-16 8:27 ` [PATCH v5 01/11] powerpc/pseries/iommu: Replace hard-coded page shift Leonardo Bras
2021-07-19 13:48 ` Frederic Barrat
2021-07-19 18:43 ` Leonardo Brás
2021-07-16 8:27 ` [PATCH v5 02/11] powerpc/kernel/iommu: Add new iommu_table_in_use() helper Leonardo Bras
2021-07-19 13:53 ` Frederic Barrat
2021-07-20 5:38 ` Leonardo Brás
2021-07-20 9:41 ` Alexey Kardashevskiy [this message]
2021-07-16 8:27 ` [PATCH v5 03/11] powerpc/pseries/iommu: Add iommu_pseries_alloc_table() helper Leonardo Bras
2021-07-19 14:04 ` Frederic Barrat
2021-07-19 18:47 ` Leonardo Brás
2021-07-16 8:27 ` [PATCH v5 04/11] powerpc/pseries/iommu: Add ddw_list_new_entry() helper Leonardo Bras
2021-07-19 14:14 ` Frederic Barrat
2021-07-19 18:47 ` Leonardo Brás
2021-07-16 8:27 ` [PATCH v5 05/11] powerpc/pseries/iommu: Allow DDW windows starting at 0x00 Leonardo Bras
2021-07-20 17:44 ` Frederic Barrat
2021-07-16 8:27 ` [PATCH v5 06/11] powerpc/pseries/iommu: Add ddw_property_create() and refactor enable_ddw() Leonardo Bras
2021-07-20 17:49 ` Frederic Barrat
2021-08-17 5:59 ` Leonardo Brás
2021-07-16 8:27 ` [PATCH v5 07/11] powerpc/pseries/iommu: Reorganize iommu_table_setparms*() with new helper Leonardo Bras
2021-07-20 17:50 ` Frederic Barrat
2021-07-16 8:27 ` [PATCH v5 08/11] powerpc/pseries/iommu: Update remove_dma_window() to accept property name Leonardo Bras
2021-07-20 17:51 ` Frederic Barrat
2021-08-17 5:59 ` Leonardo Brás
2021-08-17 6:12 ` Leonardo Brás
2021-08-24 6:31 ` Alexey Kardashevskiy
2021-07-16 8:27 ` [PATCH v5 09/11] powerpc/pseries/iommu: Find existing DDW with given " Leonardo Bras
2021-07-20 17:52 ` Frederic Barrat
2021-07-16 8:27 ` [PATCH v5 10/11] powerpc/pseries/iommu: Make use of DDW for indirect mapping Leonardo Bras
2021-07-20 18:12 ` Frederic Barrat
2021-07-21 3:32 ` Alexey Kardashevskiy
2021-07-21 15:04 ` Frederic Barrat
2021-07-23 5:34 ` Alexey Kardashevskiy
2021-08-17 5:59 ` Leonardo Brás
2021-08-17 5:59 ` Leonardo Brás
2021-07-16 8:27 ` [PATCH v5 11/11] powerpc/pseries/iommu: Rename "direct window" to "dma window" Leonardo Bras
2021-07-20 18:12 ` Frederic Barrat
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