[dpdk-dev] [PATCH v2] pci_vfio: Support 64KB kernel page_size with vfio-pci driver
Burakov, Anatoly
anatoly.burakov at intel.com
Fri Nov 16 11:36:31 CET 2018
On 16-Nov-18 2:34 AM, Tone Zhang (Arm Technology China) wrote:
> Hi Anatoly,
>
> I have some comments.
>
>> -----Original Message-----
>> From: Tone Zhang (Arm Technology China)
>> Sent: Thursday, November 15, 2018 8:49 AM
>> To: Burakov, Anatoly <anatoly.burakov at intel.com>; dev at dpdk.org
>> Cc: Gavin Hu (Arm Technology China) <Gavin.Hu at arm.com>; Honnappa
>> Nagarahalli <Honnappa.Nagarahalli at arm.com>; Steve Capper
>> <Steve.Capper at arm.com>; nd <nd at arm.com>
>> Subject: RE: [PATCH v2] pci_vfio: Support 64KB kernel page_size with vfio-pci
>> driver
>>
>> Hi Anatoly,
>>
>> Sorry for the late response.
>>
>>> -----Original Message-----
>>> From: Burakov, Anatoly <anatoly.burakov at intel.com>
>>> Sent: Friday, November 9, 2018 8:15 PM
>>> To: Tone Zhang (Arm Technology China) <Tone.Zhang at arm.com>;
>>> dev at dpdk.org
>>> Cc: Gavin Hu (Arm Technology China) <Gavin.Hu at arm.com>; Honnappa
>>> Nagarahalli <Honnappa.Nagarahalli at arm.com>; Steve Capper
>>> <Steve.Capper at arm.com>; nd <nd at arm.com>
>>> Subject: Re: [PATCH v2] pci_vfio: Support 64KB kernel page_size with
>>> vfio-pci driver
>>>
>>> On 09-Nov-18 5:57 AM, tone.zhang wrote:
>>>> With a larger PAGE_SIZE it is possible for the MSI table to very
>>>> close to the end of the BAR s.t. when we align the start and end of
>>>> the MSI table to the PAGE_SIZE, the end offset of the MSI table is
>>>> out of the PCI BAR boundary.
>>>>
>>>> This patch addresses the issue by comparing both the start and the
>>>> end offset of the MSI table with the BAR size, and skip the mapping
>>>> if it is out of Bar scope.
>>>>
>>>> The patch fixes the debug log as below:
>>>> EAL: Skipping BAR0
>>>>
>>>> Signed-off-by: tone.zhang <tone.zhang at arm.com>
>>>> Reviewed-by: Gavin Hu <Gavin.Hu at arm.com>
>>>> Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli at arm.com>
>>>> Reviewed-by: Steve Capper <Steve.Capper at arm.com>
>>>> Reviewed-by: Burakov Anatoly <anatoly.burakov at intel.com>
>>>
>>> In the future, please don't include my Reviewed tag unless i actually
>>> sent one :)
>>
>> Thanks a lot! Will keep in mind. 😊
>>
>>>
>>>> ---
>>>> drivers/bus/pci/linux/pci_vfio.c | 36
>>>> +++++++++++++++++++++++++++++++---
>>> --
>>>> 1 file changed, 31 insertions(+), 5 deletions(-)
>>>>
>>>> diff --git a/drivers/bus/pci/linux/pci_vfio.c
>>>> b/drivers/bus/pci/linux/pci_vfio.c
>>>> index 305cc06..9a0affe 100644
>>>> --- a/drivers/bus/pci/linux/pci_vfio.c
>>>> +++ b/drivers/bus/pci/linux/pci_vfio.c
>>>> @@ -445,9 +445,11 @@ pci_vfio_mmap_bar(int vfio_dev_fd, struct
>>> mapped_pci_resource *vfio_res,
>>>> struct pci_msix_table *msix_table = &vfio_res->msix_table;
>>>> struct pci_map *bar = &vfio_res->maps[bar_index];
>>>>
>>>> - if (bar->size == 0)
>>>> + if (bar->size == 0) {
>>>> /* Skip this BAR */
>>>> + RTE_LOG(INFO, EAL, "Skipping BAR%d\n", bar_index);
>>>> return 0;
>>>> + }
>>>>
>>>> if (msix_table->bar_index == bar_index) {
>>>> /*
>>>> @@ -456,8 +458,22 @@ pci_vfio_mmap_bar(int vfio_dev_fd, struct
>>> mapped_pci_resource *vfio_res,
>>>> */
>>>> uint32_t table_start = msix_table->offset;
>>>> uint32_t table_end = table_start + msix_table->size;
>>>> - table_end = (table_end + ~PAGE_MASK) & PAGE_MASK;
>>>> - table_start &= PAGE_MASK;
>>>> + table_end = RTE_ALIGN(table_end, PAGE_SIZE);
>>>> + table_start = RTE_ALIGN(table_start, PAGE_SIZE);
>>>> + /* after rounding to PAGE_SIZE, it is over the bar->size,
>>>> + * fall back to the MSI-X table offset in the bar and
>>>> + * align with PAGE_SIZE.
>>>> + */
>>>
>>> Minor nitpick - wording of comment could be better, for example:
>>>
>>> if page-aligned start of MSI-X table is beyond BAR size, shrink the
>>> mapping size to MSI-X table start address.
>>>
>>> Also, probably needs newline before comment.
>>>
>>
>> Will update the code in next version. Thanks!
>>
>>>> + if (table_start >= bar->size) {
>>>> + table_start = RTE_ALIGN_FLOOR(msix_table->offset,
>>>> + PAGE_SIZE);
>>>> + /* after aligning with PAGE_SIZE, if it is less than
>>>> + * the MSI-X table offset, continue falling back to
>>>> + * the actual MSI-X table offset in the bar.
>>>> + */
>>>
>>> Same here, wording could probably be improved. Suggested rewording:
>>>
>>> If MSI-X table address, floor-aligned by page size, is lower than
>>> actual MSI-X table offset, fall back to using MSI-X table offset as table start.
>>>
>>> Now that i think of it, this could really be expressed like this:
>>>
>>> uint32_t aligned = RTE_ALIGN_FLOOR(msix_table->offset, PAGE_SIZE);
>>> table_start = RTE_MAX(aligned, msix_table_offset);
>>>
>>> I believe this would be much clearer.
>>>
>>
>> Will update the patch.
>>
>
> When enter the judgement, it implies the "msix_table->offset" is NOT page size aligned, I think we can replace the code in the judgement with one line: table_start = msix_table->offset;
> It looks more simple. What's your opinion? Thanks!
Agree, what was i thinking :D
>
>>>> + if (table_start < msix_table->offset)
>>>> + table_start = msix_table->offset;
>>>> + }
>>>>
>>>> if (table_start == 0 && table_end >= bar->size) {
>>>> /* Cannot map this BAR */
>>>> @@ -469,8 +485,18 @@ pci_vfio_mmap_bar(int vfio_dev_fd, struct
>>>> mapped_pci_resource *vfio_res,
>>>>
>>>> memreg[0].offset = bar->offset;
>>>> memreg[0].size = table_start;
>>>> - memreg[1].offset = bar->offset + table_end;
>>>> - memreg[1].size = bar->size - table_end;
>>>> + if (bar->size < table_end) {
>>>> + /*
>>>> + * after rounding to PAGE_SIZE we don't have any space
>>>> + * left after the MSI table, so don't try and map it.
>>>> + */
>>>
>>> Suggested rewording:
>>>
>>> If MSI-X table end is beyond BAR end, don't attempt to perform second
>> mapping.
>>>
>>
>> Thanks a lot. Will update.
>>
>>>> + memreg[1].offset = 0;
>>>> + memreg[1].size = 0;
>>>> + }
>>>> + else {
>>>> + memreg[1].offset = bar->offset + table_end;
>>>> + memreg[1].size = bar->size - table_end;
>>>> + }
>>>>
>>>> RTE_LOG(DEBUG, EAL,
>>>> "Trying to map BAR%d that contains the MSI-X "
>>>>
>>>
>>> However, the patch can go in as is if needed, so
>>>
>>> Reviewed-by: Anatoly Burakov <anatoly.burakov at intel.com>
>>>
>>
>> Thanks! 😉
>>
>>> --
>>> Thanks,
>>> Anatoly
>>
>> Br,
>> Tone
>
> Br,
> Tone
>
--
Thanks,
Anatoly
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