On 03.07.19 11:12, Pratyush Yadav wrote:
On 02/07/19 9:18 PM, Jan Kiszka wrote:
On 02.07.19 16:36, Pratyush Yadav wrote:
The SMMU driver needs access to guest paging structures, so they need to
be initialized before we can initialize the driver.
No signed-off - because you were not sure if this is ready? ;)
Quite the opposite. I was so sure this simple change was correct, I didn't
double-check the patch and missed the signed-off.
The bad news: it isn't. The x86 IOMMUs have to be initialized prior to calling
arch_map_memory_region because that calls iommu_map_memory_region.
Can you describe in more details why the SMMU driver needs that guest paging
access during init, and why that can't be solved by hooking into ARM's
arch_map_memory_region?
SMMU's init doesn't need guest paging access, but arm_smmuv3_cell_init() does.
Linux might have already initialised some stream table entries before Jailhouse
was enabled. We need to copy those entries in the hypervisor's stream table.
This is done in arm_smmuv3_cell_init(). But for some reason, cell_init() is not
called for the root cell. So I call it from arm_smmuv3_init().
This seemed like a simple enough change to work around the problem. Calling
cell_init() from a later point works just as fine. Any particular reason why
cell_init() is not called for the root cell? I see a lot of drivers (ioapic,
vtd, etc) calling it in their init functions.
I suppose you mean the cell_init unit callback (cell_init() is called already
during early_init()): That is called on cell_create only. We could also call the
cell_init callbacks after unit initialization from init_late(), but that
requires some careful checks if there are ordering issue. However, that wouldn't
solve your issue.
But your problem is not that different from vtd.c e.g. It also needs to access
the guest pages in order to transfer interrupt remapping information into the
new IR table. That is done during config_commit, and you should just do the same.
Jan
--
Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux
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