On 03/07/2017 01:26 PM, Andrew Cooper wrote:
On 07/03/17 18:18, Boris Ostrovsky wrote:
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Don't we need to pass vaddr down to all routines so that they select
appropriate tables? You seem to always be choosing the first one.
IIUC, we clear whole page table subtree covered by one pgd entry.
So, no, there's no need to pass vaddr down. Just pointer to page table
entry is enough.
But I know virtually nothing about Xen. Please re-check my reasoning.
Yes, we effectively remove the whole page table for vaddr so I guess
it's OK.
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I would also appreciate help with getting x86 Xen code work with 5-level
paging enabled. For now I make CONFIG_XEN dependent on !CONFIG_X86_5LEVEL.
Hmmm... that's a problem since this requires changes in the hypervisor
and even if/when these changes are made older version of hypervisor
still will not be able to run those guests.
This affects only PV guests and there is a series under review that
provides clean code separation with CONFIG_XEN_PV but because, for
example, dom0 (Xen control domain) is PV this will significantly limit
availability of dom0-capable kernels (because I assume distros will want
to have CONFIG_X86_5LEVEL).
Wasn't the plan to be able to automatically detect 4 vs 5 level support,
and cope either way, so distros didn't have to ship two different builds
of Linux?
If so, all we need to do git things to compile sensibly, and have the PV
entry code in Linux configure the rest of the kernel appropriately.
I am not aware of any plans but this would obviously be the preferred route.
-boris
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