From: Auger Eric <eric.auger@redhat.com>
To: Joerg Roedel <joro@8bytes.org>
Cc: alex.williamson@redhat.com, dwmw2@infradead.org,
will.deacon@arm.com, linux-kernel@vger.kernel.org,
iommu@lists.linux-foundation.org, sudeep.holla@arm.com,
robin.murphy@arm.com, eric.auger.pro@gmail.com
Subject: Re: [PATCH v4 3/8] iommu/vt-d: Duplicate iommu_resv_region objects per device list
Date: Tue, 28 May 2019 13:51:12 +0200 [thread overview]
Message-ID: <26e14927-0ec5-2472-54a2-4498a2145c19@redhat.com> (raw)
In-Reply-To: <20190527152303.GD12745@8bytes.org>
Hi Joerg,
On 5/27/19 5:23 PM, Joerg Roedel wrote:
> On Mon, May 27, 2019 at 10:55:36AM +0200, Eric Auger wrote:
>> - list_add_tail(&rmrr->resv->list, head);
>> + length = rmrr->end_address - rmrr->base_address + 1;
>> + resv = iommu_alloc_resv_region(rmrr->base_address,
>> + length, prot,
>> + IOMMU_RESV_DIRECT,
>> + GFP_ATOMIC);
>> + if (!resv)
>> + break;
>> +
>> + list_add_tail(&resv->list, head);
>
> Okay, so this happens in a rcu_read_locked section and must be atomic,
> but I don't like this extra parameter to iommu_alloc_resv_region().
>
> How about replacing the rcu-lock with the dmar_global_lock, which
> protects against changes to the global rmrr list? This will make this
> loop preemptible and taking the global lock is okay because this
> function is in no way performance relevant.
After studying in more details the for_each_active_dev_scope macro and
rcu_dereference_check it looks OK to me. I respinned accordingly.
Thanks
Eric
>
> Regards,
>
> Joerg
>
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next prev parent reply other threads:[~2019-05-28 11:52 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-27 8:55 [PATCH v4 0/8] RMRR related fixes and enhancements Eric Auger
2019-05-27 8:55 ` [PATCH v4 1/8] iommu: Fix a leak in iommu_insert_resv_region Eric Auger
2019-05-27 8:55 ` [PATCH v4 2/8] iommu: Pass a GFP flag parameter to iommu_alloc_resv_region() Eric Auger
2019-05-27 8:55 ` [PATCH v4 3/8] iommu/vt-d: Duplicate iommu_resv_region objects per device list Eric Auger
2019-05-27 15:23 ` Joerg Roedel
2019-05-28 11:51 ` Auger Eric [this message]
2019-05-27 8:55 ` [PATCH v4 4/8] iommu/vt-d: Introduce is_downstream_to_pci_bridge helper Eric Auger
2019-05-27 8:55 ` [PATCH v4 5/8] iommu/vt-d: Handle RMRR with PCI bridge device scopes Eric Auger
2019-05-27 8:55 ` [PATCH v4 6/8] iommu/vt-d: Handle PCI bridge RMRR device scopes in intel_iommu_get_resv_regions Eric Auger
2019-05-27 8:55 ` [PATCH v4 7/8] iommu: Introduce IOMMU_RESV_DIRECT_RELAXABLE reserved memory regions Eric Auger
2019-05-27 8:55 ` [PATCH v4 8/8] iommu/vt-d: Differentiate relaxable and non relaxable RMRRs Eric Auger
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