Re: [PATCH 27/27] KVM: PPC: Add Documentation about PV interface

On 09.07.2010, at 11:11, MJ embd wrote:

On Thu, Jul 1, 2010 at 4:13 PM, Alexander Graf [off-list ref] wrote:

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We just introduced a new PV interface that screams for documentation. =

So here

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it is - a shiny new and awesome text file describing the internal =

works of

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the PPC KVM paravirtual interface.
=20
Signed-off-by: Alexander Graf <redacted>
=20
+
+
+Some instructions require more logic to determine what's going on =

than a load

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+or store instruction can deliver. To enable patching of those, we =

keep some

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+RAM around where we can live translate instructions to. What happens =

is the

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+following:
+
+       1) copy emulation code to memory
+       2) patch that code to fit the emulated instruction
+       3) patch that code to return to the original pc + 4
+       4) patch the original instruction to branch to the new code
+
+That way we can inject an arbitrary amount of code as replacement =

for a single

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+instruction. This allows us to check for pending interrupts when =

setting EE=3D1

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+for example.
+

=20
Which patch does this mapping ? Can you please point to that.

The branch patching is in patch 22/27. For the respective users, see =
patch 23-26/27.


Alex