From: Yi Liu <yi.l.liu@intel.com>
To: Alex Williamson <alex.williamson@redhat.com>
Cc: <jgg@nvidia.com>, <kevin.tian@intel.com>, <joro@8bytes.org>,
<robin.murphy@arm.com>, <eric.auger@redhat.com>,
<nicolinc@nvidia.com>, <kvm@vger.kernel.org>,
<chao.p.peng@linux.intel.com>, <iommu@lists.linux.dev>,
<baolu.lu@linux.intel.com>, <zhenzhong.duan@intel.com>,
<jacob.jun.pan@intel.com>, Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH v2 1/4] ida: Add ida_get_lowest()
Date: Thu, 18 Apr 2024 15:02:46 +0800 [thread overview]
Message-ID: <e3531550-8644-4a7e-94bd-75bdb52182be@intel.com> (raw)
In-Reply-To: <20240416100329.35cede17.alex.williamson@redhat.com>
On 2024/4/17 00:03, Alex Williamson wrote:
> On Fri, 12 Apr 2024 01:21:18 -0700
> Yi Liu <yi.l.liu@intel.com> wrote:
>
>> There is no helpers for user to check if a given ID is allocated or not,
>> neither a helper to loop all the allocated IDs in an IDA and do something
>> for cleanup. With the two needs, a helper to get the lowest allocated ID
>> of a range can help to achieve it.
>>
>> Caller can check if a given ID is allocated or not by:
>> int id = 200, rc;
>>
>> rc = ida_get_lowest(&ida, id, id);
>> if (rc == id)
>> //id 200 is used
>> else
>> //id 200 is not used
>>
>> Caller can iterate all allocated IDs by:
>> int id = 0;
>>
>> while (!ida_is_empty(&pasid_ida)) {
>> id = ida_get_lowest(pasid_ida, id, INT_MAX);
>> if (id < 0)
>> break;
>> //anything to do with the allocated ID
>> ida_free(pasid_ida, pasid);
>> }
>>
>> Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
>> Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
>> Signed-off-by: Yi Liu <yi.l.liu@intel.com>
>> ---
>> include/linux/idr.h | 1 +
>> lib/idr.c | 67 +++++++++++++++++++++++++++++++++++++++++++++
>> 2 files changed, 68 insertions(+)
>>
>> diff --git a/include/linux/idr.h b/include/linux/idr.h
>> index da5f5fa4a3a6..1dae71d4a75d 100644
>> --- a/include/linux/idr.h
>> +++ b/include/linux/idr.h
>> @@ -257,6 +257,7 @@ struct ida {
>> int ida_alloc_range(struct ida *, unsigned int min, unsigned int max, gfp_t);
>> void ida_free(struct ida *, unsigned int id);
>> void ida_destroy(struct ida *ida);
>> +int ida_get_lowest(struct ida *ida, unsigned int min, unsigned int max);
>>
>> /**
>> * ida_alloc() - Allocate an unused ID.
>> diff --git a/lib/idr.c b/lib/idr.c
>> index da36054c3ca0..03e461242fe2 100644
>> --- a/lib/idr.c
>> +++ b/lib/idr.c
>> @@ -476,6 +476,73 @@ int ida_alloc_range(struct ida *ida, unsigned int min, unsigned int max,
>> }
>> EXPORT_SYMBOL(ida_alloc_range);
>>
>> +/**
>> + * ida_get_lowest - Get the lowest used ID.
>> + * @ida: IDA handle.
>> + * @min: Lowest ID to get.
>> + * @max: Highest ID to get.
>> + *
>> + * Get the lowest used ID between @min and @max, inclusive. The returned
>> + * ID will not exceed %INT_MAX, even if @max is larger.
>> + *
>> + * Context: Any context. Takes and releases the xa_lock.
>> + * Return: The lowest used ID, or errno if no used ID is found.
>> + */
>> +int ida_get_lowest(struct ida *ida, unsigned int min, unsigned int max)
>> +{
>> + unsigned long index = min / IDA_BITMAP_BITS;
>> + unsigned int offset = min % IDA_BITMAP_BITS;
>> + unsigned long *addr, size, bit;
>> + unsigned long flags;
>> + void *entry;
>> + int ret;
>> +
>> + if (min >= INT_MAX)
>> + return -EINVAL;
>> + if (max >= INT_MAX)
>> + max = INT_MAX;
>> +
>
> Could these be made consistent with the test in ida_alloc_range(), ie:
>
> if ((int)min < 0)
> return -EINVAL;
> if ((int)max < 0)
> max = INT_MAX;
>
sure.
>> + xa_lock_irqsave(&ida->xa, flags);
>> +
>> + entry = xa_find(&ida->xa, &index, max / IDA_BITMAP_BITS, XA_PRESENT);
>> + if (!entry) {
>> + ret = -ENOTTY;
>
> -ENOENT? Same for all below too.
I see.
>> + goto err_unlock;
>> + }
>> +
>> + if (index > min / IDA_BITMAP_BITS)
>> + offset = 0;
>> + if (index * IDA_BITMAP_BITS + offset > max) {
>> + ret = -ENOTTY;
>> + goto err_unlock;
>> + }
>> +
>> + if (xa_is_value(entry)) {
>> + unsigned long tmp = xa_to_value(entry);
>> +
>> + addr = &tmp;
>> + size = BITS_PER_XA_VALUE;
>> + } else {
>> + addr = ((struct ida_bitmap *)entry)->bitmap;
>> + size = IDA_BITMAP_BITS;
>> + }
>> +
>> + bit = find_next_bit(addr, size, offset);
>> +
>> + xa_unlock_irqrestore(&ida->xa, flags);
>> +
>> + if (bit == size ||
>> + index * IDA_BITMAP_BITS + bit > max)
>> + return -ENOTTY;
>> +
>> + return index * IDA_BITMAP_BITS + bit;
>> +
>> +err_unlock:
>> + xa_unlock_irqrestore(&ida->xa, flags);
>> + return ret;
>> +}
>> +EXPORT_SYMBOL(ida_get_lowest);
>
> The API is a bit awkward to me, I wonder if it might be helped with
> some renaming and wrappers...
>
> int ida_find_first_range(struct ida *ida, unsigned int min, unsigned int max);
ok.
> bool ida_exists(struct ida *ida, unsigned int id)
> {
> return ida_find_first_range(ida, id, id) == id;
> }
this does helps in next patch.
>
> int ida_find_first(struct ida *ida)
> {
> return ida_find_first_range(ida, 0, ~0);
> }
>
perhaps it can be added in future. This series has two usages. One is to
check if a given ID is allocated. This can be covered by your ida_exists().
Another usage is to loop each IDs, do detach and free. This can still use
the ida_find_first_range() like the example in the commit message. The
first loop starts from 0, and next would start from the last found ID.
This may be more efficient than starts from 0 in every loop.
> _min and _max variations of the latter would align with existing
> ida_alloc variants, but maybe no need to add them preemptively.
yes.
> Possibly an ida_for_each() could be useful in the use case of
> disassociating each id, but not required for the brute force iterative
> method. Thanks,
yep. maybe we can start with the below code, no need for ida_for_each()
today.
int id = 0;
while (!ida_is_empty(&pasid_ida)) {
id = ida_find_first_range(pasid_ida, id, INT_MAX);
if (unlikely(WARN_ON(id < 0))
break;
iommufd_device_pasid_detach();
ida_free(pasid_ida, pasid);
}
>
>> +
>> /**
>> * ida_free() - Release an allocated ID.
>> * @ida: IDA handle.
>
--
Regards,
Yi Liu
next prev parent reply other threads:[~2024-04-18 6:59 UTC|newest]
Thread overview: 72+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-12 8:21 [PATCH v2 0/4] vfio-pci support pasid attach/detach Yi Liu
2024-04-12 8:21 ` [PATCH v2 1/4] ida: Add ida_get_lowest() Yi Liu
2024-04-16 16:03 ` Alex Williamson
2024-04-18 7:02 ` Yi Liu [this message]
2024-04-18 16:23 ` Alex Williamson
2024-04-18 17:12 ` Jason Gunthorpe
2024-04-19 13:43 ` Yi Liu
2024-04-19 13:55 ` Alex Williamson
2024-04-19 14:00 ` Jason Gunthorpe
2024-04-23 7:19 ` Yi Liu
2024-04-19 13:40 ` Yi Liu
2024-04-12 8:21 ` [PATCH v2 2/4] vfio-iommufd: Support pasid [at|de]tach for physical VFIO devices Yi Liu
2024-04-16 9:01 ` Tian, Kevin
2024-04-16 9:24 ` Yi Liu
2024-04-16 9:47 ` Tian, Kevin
2024-04-18 7:04 ` Yi Liu
2024-04-23 12:43 ` Jason Gunthorpe
2024-04-24 0:33 ` Tian, Kevin
2024-04-24 4:48 ` Yi Liu
2024-04-12 8:21 ` [PATCH v2 3/4] vfio: Add VFIO_DEVICE_PASID_[AT|DE]TACH_IOMMUFD_PT Yi Liu
2024-04-16 9:13 ` Tian, Kevin
2024-04-16 9:36 ` Yi Liu
2024-04-23 12:45 ` Jason Gunthorpe
2024-04-12 8:21 ` [PATCH v2 4/4] vfio: Report PASID capability via VFIO_DEVICE_FEATURE ioctl Yi Liu
2024-04-16 9:40 ` Tian, Kevin
2024-04-16 17:57 ` Alex Williamson
2024-04-17 7:09 ` Tian, Kevin
2024-04-17 20:25 ` Alex Williamson
2024-04-18 0:21 ` Tian, Kevin
2024-04-18 8:23 ` Yi Liu
2024-04-18 16:34 ` Alex Williamson
2024-04-23 12:39 ` Jason Gunthorpe
2024-04-24 0:24 ` Tian, Kevin
2024-04-24 13:59 ` Jason Gunthorpe
2024-04-16 8:38 ` [PATCH v2 0/4] vfio-pci support pasid attach/detach Tian, Kevin
2024-04-16 17:50 ` Jason Gunthorpe
2024-04-17 7:16 ` Tian, Kevin
2024-04-17 12:20 ` Jason Gunthorpe
2024-04-17 23:02 ` Alex Williamson
2024-04-18 0:06 ` Tian, Kevin
2024-04-18 9:03 ` Yi Liu
2024-04-18 20:37 ` Alex Williamson
2024-04-19 5:52 ` Tian, Kevin
2024-04-19 16:35 ` Alex Williamson
2024-04-23 7:43 ` Tian, Kevin
2024-04-23 12:01 ` Jason Gunthorpe
2024-04-23 23:47 ` Tian, Kevin
2024-04-24 0:12 ` Jason Gunthorpe
2024-04-24 2:57 ` Tian, Kevin
2024-04-24 12:29 ` Baolu Lu
2024-04-24 14:04 ` Jason Gunthorpe
2024-04-24 5:19 ` Tian, Kevin
2024-04-24 14:15 ` Jason Gunthorpe
2024-04-24 18:38 ` Alex Williamson
2024-04-24 18:45 ` Jason Gunthorpe
2024-04-24 18:24 ` Alex Williamson
2024-04-24 18:36 ` Jason Gunthorpe
2024-04-24 20:13 ` Alex Williamson
2024-04-26 14:11 ` Jason Gunthorpe
2024-04-26 20:13 ` Alex Williamson
2024-04-28 6:19 ` Tian, Kevin
2024-04-29 7:43 ` Yi Liu
2024-04-29 17:15 ` Jason Gunthorpe
2024-04-29 17:44 ` Jason Gunthorpe
2024-04-27 5:05 ` Christoph Hellwig
2024-04-25 9:26 ` Yi Liu
2024-04-25 12:58 ` Alex Williamson
2024-04-26 9:01 ` Yi Liu
2024-04-19 13:59 ` Jason Gunthorpe
2024-04-23 7:58 ` Yi Liu
2024-04-23 12:05 ` Jason Gunthorpe
2024-04-19 13:34 ` Jason Gunthorpe
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