Hi Radim,
On 08/22/2016 04:19 PM, Suravee Suthikulpanit wrote:
he problem with wrappers is that we don't know what list we should
remove the "struct amd_ir_data" from; we would need to add another
tracking structure or go through all VCPUs.
Having "struct list_head" in "struct amd_ir_data" would allow us to know
the current list and remove it from there:
One "struct amd_ir_data" should never be used by more than one caller of
amd_iommu_update_ga(), because they would have to be cooperating anyway,
which would mean a single mediator, so we can add a "struct list_head"
into "struct amd_ir_data".
Minor design note:
To make the usage of "struct amd_ir_data" safer, we could pass "struct
list_head" into irq_set_vcpu_affinity(), instead of returning "struct
amd_ir_data *".
irq_set_vcpu_affinity() would add "struct amd_ir_data" to the list
only
if ir_data was not already in some list and report whether the list
was modified.
I think that adding "struct list_head" into "struct amd_ir_data" is
nicer than having wrappers.
Joerg, Paolo, what do you think?
I think modifying irq_set_vcpu_affinity() to also pass struct list_head
seems a bit redundant since it is currently design to allow passing in
void *, which leaves the other option where we might just need to pass
in a wrapper (e.g. going back to the previous design where we pass in
struct amd_iommu_pi_data) and also add a pointer to the ir_list in the
wrapper as well. Then, IOMMU is responsible for adding/deleting ir_data
to/from this list instead of SVM. This should be fine since we only need
to coordinate b/w SVM and AMD-IOMMU.
Thanks,
Suravee
Actually, thinking about this again, going back to keeping the per-vcpu
list of struct amd_iommu_pi_data is probably the simplest here.
* We avoid having to expose the amd_ir_data to SVM.
* We can match using amd_ir_data * when traversing the list.
* We can easily add the code to manage the list in the SVM. We can make
sure that the struct amd_iommu_pi_data is not already mapped before
adding it to a new per-vcpu list. If it is currently mapped, we can
simply unmapped it. Doing this from IOMMU would be more complicate and
require lots of parameter passing.
Thanks,
Suravee
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