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SubjectRe: [PATCH] vfio powerpc: implement IOMMU driver for VFIO
On 21/03/13 07:45, Alex Williamson wrote:
> On Tue, 2013-03-19 at 18:08 +1100, Alexey Kardashevskiy wrote:
>> VFIO implements platform independent stuff such as
>> a PCI driver, BAR access (via read/write on a file descriptor
>> or direct mapping when possible) and IRQ signaling.
>>
>> The platform dependent part includes IOMMU initialization
>> and handling. This patch implements an IOMMU driver for VFIO
>> which does mapping/unmapping pages for the guest IO and
>> provides information about DMA window (required by a POWERPC
>> guest).
>>
>> The counterpart in QEMU is required to support this functionality.
>>
>> Changelog:
>> * documentation updated
>> * containter enable/disable ioctls added
>> * request_module(spapr_iommu) added
>> * various locks fixed
>>
>> Cc: David Gibson <david@gibson.dropbear.id.au>
>> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
>> ---
>
>
> Looking pretty good. There's one problem with the detach_group,
> otherwise just some trivial comments below. What's the status of the
> tce code that this depends on? Thanks,


It is done, I am just waiting till other patches of the series will be
reviewed (by guys) and fixed (by me) and then I'll post everything again.

[skipped]

>> +static int tce_iommu_enable(struct tce_container *container)
>> +{
>> + int ret = 0;
>> + unsigned long locked, lock_limit, npages;
>> + struct iommu_table *tbl = container->tbl;
>> +
>> + if (!container->tbl)
>> + return -ENXIO;
>> +
>> + if (!current->mm)
>> + return -ESRCH; /* process exited */
>> +
>> + mutex_lock(&container->lock);
>> + if (container->enabled) {
>> + mutex_unlock(&container->lock);
>> + return -EBUSY;
>> + }
>> +
>> + /*
>> + * Accounting for locked pages.
>> + *
>> + * On sPAPR platform, IOMMU translation table contains
>> + * an entry per 4K page. Every map/unmap request is sent
>> + * by the guest via hypercall and supposed to be handled
>> + * quickly, ecpesially in real mode (if such option is
>
> s/ecpesially/especially/


I replaced the whole text by the one written by Ben and David.

[skipped]

>> + }
>> +
>> + return -ENOTTY;
>> +}
>> +
>> +static int tce_iommu_attach_group(void *iommu_data,
>> + struct iommu_group *iommu_group)
>> +{
>> + int ret;
>> + struct tce_container *container = iommu_data;
>> + struct iommu_table *tbl = iommu_group_get_iommudata(iommu_group);
>> +
>> + BUG_ON(!tbl);
>> + mutex_lock(&container->lock);
>> + pr_debug("tce_vfio: Attaching group #%u to iommu %p\n",
>> + iommu_group_id(iommu_group), iommu_group);
>> + if (container->tbl) {
>> + pr_warn("tce_vfio: Only one group per IOMMU container is allowed, existing id=%d, attaching id=%d\n",
>> + iommu_group_id(container->tbl->it_group),
>> + iommu_group_id(iommu_group));
>> + mutex_unlock(&container->lock);
>> + return -EBUSY;
>> + }
>> +
>> + ret = iommu_take_ownership(tbl);
>> + if (!ret)
>> + container->tbl = tbl;
>> +
>> + mutex_unlock(&container->lock);
>> +
>> + return ret;
>> +}
>> +
>> +static void tce_iommu_detach_group(void *iommu_data,
>> + struct iommu_group *iommu_group)
>> +{
>> + struct tce_container *container = iommu_data;
>> + struct iommu_table *tbl = iommu_group_get_iommudata(iommu_group);
>> +
>> + BUG_ON(!tbl);
>> + mutex_lock(&container->lock);
>> + if (tbl != container->tbl) {
>> + pr_warn("tce_vfio: detaching group #%u, expected group is #%u\n",
>> + iommu_group_id(iommu_group),
>> + iommu_group_id(tbl->it_group));
>> + } else if (container->enabled) {
>> + pr_err("tce_vfio: detaching group #%u from enabled container\n",
>> + iommu_group_id(tbl->it_group));
>
> Hmm, something more than a pr_err needs to happen here. Wouldn't this
> imply a disable and going back to an unprivileged container?

Ah. It does not return error code... Then something like that?

...
} else if (container->enabled) {
pr_warn("tce_vfio: detaching group #%u from enabled
container, forcing disable\n",
iommu_group_id(tbl->it_group));
tce_iommu_disable(container);
...

--
Alexey


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