LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Auger Eric <eric.auger@redhat.com>
To: Lu Baolu <baolu.lu@linux.intel.com>,
	eric.auger.pro@gmail.com, joro@8bytes.org,
	iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
	dwmw2@infradead.org, robin.murphy@arm.com
Cc: alex.williamson@redhat.com, shameerali.kolothum.thodi@huawei.com,
	jean-philippe.brucker@arm.com
Subject: Re: [PATCH v5 7/7] iommu/vt-d: Differentiate relaxable and non relaxable RMRRs
Date: Wed, 29 May 2019 17:43:41 +0200	[thread overview]
Message-ID: <1f2a7039-04be-383e-b054-d0dba99b9bdf@redhat.com> (raw)
In-Reply-To: <13a77738-5e85-ea62-aab1-384c75bde8bd@linux.intel.com>

Hi Lu,

On 5/29/19 4:34 AM, Lu Baolu wrote:
> Hi,
> 
> On 5/28/19 7:50 PM, Eric Auger wrote:
>> Now we have a new IOMMU_RESV_DIRECT_RELAXABLE reserved memory
>> region type, let's report USB and GFX RMRRs as relaxable ones.
>>
>> We introduce a new device_rmrr_is_relaxable() helper to check
>> whether the rmrr belongs to the relaxable category.
>>
>> This allows to have a finer reporting at IOMMU API level of
>> reserved memory regions. This will be exploitable by VFIO to
>> define the usable IOVA range and detect potential conflicts
>> between the guest physical address space and host reserved
>> regions.
>>
>> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>>
>> ---
>>
>> v3 -> v4:
>> - introduce device_rmrr_is_relaxable and reshuffle the comments
>> ---
>>   drivers/iommu/intel-iommu.c | 55 +++++++++++++++++++++++++++----------
>>   1 file changed, 40 insertions(+), 15 deletions(-)
>>
>> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
>> index 9302351818ab..01c82f848470 100644
>> --- a/drivers/iommu/intel-iommu.c
>> +++ b/drivers/iommu/intel-iommu.c
>> @@ -2920,6 +2920,36 @@ static bool device_has_rmrr(struct device *dev)
>>       return false;
>>   }
>>   +/*
>> + * device_rmrr_is_relaxable - Test whether the RMRR of this device
>> + * is relaxable (ie. is allowed to be not enforced under some
>> conditions)
>> + *
>> + * @dev: device handle
>> + *
>> + * We assume that PCI USB devices with RMRRs have them largely
>> + * for historical reasons and that the RMRR space is not actively
>> used post
>> + * boot.  This exclusion may change if vendors begin to abuse it.
>> + *
>> + * The same exception is made for graphics devices, with the
>> requirement that
>> + * any use of the RMRR regions will be torn down before assigning the
>> device
>> + * to a guest.
>> + *
>> + * Return: true if the RMRR is relaxable
>> + */
>> +static bool device_rmrr_is_relaxable(struct device *dev)
>> +{
>> +    struct pci_dev *pdev;
>> +
>> +    if (!dev_is_pci(dev))
>> +        return false;
>> +
>> +    pdev = to_pci_dev(dev);
>> +    if (IS_USB_DEVICE(pdev) || IS_GFX_DEVICE(pdev))
>> +        return true;
>> +    else
>> +        return false;
>> +}
> 
> I know this is only code refactoring. But strictly speaking, the rmrr of
> any USB host device is ignorable only if quirk_usb_early_handoff() has
> been called. There, the control of USB host controller will be handed
> over from BIOS to OS and the corresponding SMI are disabled.
> 
> This function is registered in drivers/usb/host/pci-quirks.c
> 
> DECLARE_PCI_FIXUP_CLASS_FINAL(PCI_ANY_ID, PCI_ANY_ID,
>                         PCI_CLASS_SERIAL_USB, 8, quirk_usb_early_handoff);
> 
> and only get compiled if CONFIG_USB_PCI is enabled.
> 
> Hence, it's safer to say:
> 
> +#ifdef CONFIG_USB_PCI
> +    if (IS_USB_DEVICE(pdev))
> +        return true;
> +#endif /* CONFIG_USB_PCI */
> 
> I am okay if we keep this untouched and make this change within a
> separated patch.

As we first checked whether the device was a pci device, isn't it
sufficient to guarantee the quirk is setup?

As you suggested, I am inclined to keep it as a separate patch anyway.

Thank you for the review!

Best Regards

Eric
> 
>> +
>>   /*
>>    * There are a couple cases where we need to restrict the
>> functionality of
>>    * devices associated with RMRRs.  The first is when evaluating a
>> device for
>> @@ -2934,25 +2964,16 @@ static bool device_has_rmrr(struct device *dev)
>>    * We therefore prevent devices associated with an RMRR from
>> participating in
>>    * the IOMMU API, which eliminates them from device assignment.
>>    *
>> - * In both cases we assume that PCI USB devices with RMRRs have them
>> largely
>> - * for historical reasons and that the RMRR space is not actively
>> used post
>> - * boot.  This exclusion may change if vendors begin to abuse it.
>> - *
>> - * The same exception is made for graphics devices, with the
>> requirement that
>> - * any use of the RMRR regions will be torn down before assigning the
>> device
>> - * to a guest.
>> + * In both cases, devices which have relaxable RMRRs are not
>> concerned by this
>> + * restriction. See device_rmrr_is_relaxable comment.
>>    */
>>   static bool device_is_rmrr_locked(struct device *dev)
>>   {
>>       if (!device_has_rmrr(dev))
>>           return false;
>>   -    if (dev_is_pci(dev)) {
>> -        struct pci_dev *pdev = to_pci_dev(dev);
>> -
>> -        if (IS_USB_DEVICE(pdev) || IS_GFX_DEVICE(pdev))
>> -            return false;
>> -    }
>> +    if (device_rmrr_is_relaxable(dev))
>> +        return false;
>>         return true;
>>   }
>> @@ -5494,6 +5515,7 @@ static void intel_iommu_get_resv_regions(struct
>> device *device,
>>           for_each_active_dev_scope(rmrr->devices, rmrr->devices_cnt,
>>                         i, i_dev) {
>>               struct iommu_resv_region *resv;
>> +            enum iommu_resv_type type;
>>               size_t length;
>>                 if (i_dev != device &&
>> @@ -5501,9 +5523,12 @@ static void intel_iommu_get_resv_regions(struct
>> device *device,
>>                   continue;
>>                 length = rmrr->end_address - rmrr->base_address + 1;
>> +
>> +            type = device_rmrr_is_relaxable(device) ?
>> +                IOMMU_RESV_DIRECT_RELAXABLE : IOMMU_RESV_DIRECT;
>> +
>>               resv = iommu_alloc_resv_region(rmrr->base_address,
>> -                               length, prot,
>> -                               IOMMU_RESV_DIRECT);
>> +                               length, prot, type);
>>               if (!resv)
>>                   break;
>>  
> 
> Other looks good to me.
> 
> Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
> 
> Best regards,
> Baolu

      reply	other threads:[~2019-05-29 15:43 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-28 11:50 [PATCH v5 0/7] RMRR related fixes and enhancements Eric Auger
2019-05-28 11:50 ` [PATCH v5 1/7] iommu: Fix a leak in iommu_insert_resv_region Eric Auger
2019-05-29  6:17   ` Christoph Hellwig
2019-05-29 15:38     ` Auger Eric
2019-05-28 11:50 ` [PATCH v5 2/7] iommu/vt-d: Duplicate iommu_resv_region objects per device list Eric Auger
2019-05-29  2:04   ` Lu Baolu
2019-05-29 15:40     ` Auger Eric
2019-05-28 11:50 ` [PATCH v5 3/7] iommu/vt-d: Introduce is_downstream_to_pci_bridge helper Eric Auger
2019-05-29  2:11   ` Lu Baolu
2019-05-29  6:21   ` Christoph Hellwig
2019-05-29 15:43     ` Auger Eric
2019-05-28 11:50 ` [PATCH v5 4/7] iommu/vt-d: Handle RMRR with PCI bridge device scopes Eric Auger
2019-05-29  2:12   ` Lu Baolu
2019-05-28 11:50 ` [PATCH v5 5/7] iommu/vt-d: Handle PCI bridge RMRR device scopes in intel_iommu_get_resv_regions Eric Auger
2019-05-29  2:13   ` Lu Baolu
2019-05-28 11:50 ` [PATCH v5 6/7] iommu: Introduce IOMMU_RESV_DIRECT_RELAXABLE reserved memory regions Eric Auger
2019-05-28 11:50 ` [PATCH v5 7/7] iommu/vt-d: Differentiate relaxable and non relaxable RMRRs Eric Auger
2019-05-29  2:34   ` Lu Baolu
2019-05-29 15:43     ` Auger Eric [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=1f2a7039-04be-383e-b054-d0dba99b9bdf@redhat.com \
    --to=eric.auger@redhat.com \
    --cc=alex.williamson@redhat.com \
    --cc=baolu.lu@linux.intel.com \
    --cc=dwmw2@infradead.org \
    --cc=eric.auger.pro@gmail.com \
    --cc=iommu@lists.linux-foundation.org \
    --cc=jean-philippe.brucker@arm.com \
    --cc=joro@8bytes.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=robin.murphy@arm.com \
    --cc=shameerali.kolothum.thodi@huawei.com \
    --subject='Re: [PATCH v5 7/7] iommu/vt-d: Differentiate relaxable and non relaxable RMRRs' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).