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Re: [Xen-devel] [PATCH 09/14] livepatch: Add per-function applied/reverted state tracking marker


On 22/08/2019 11:20, Wieczorkiewicz, Pawel wrote:
On 22. Aug 2019, at 12:07, Julien Grall <julien.grall@xxxxxxx <mailto:julien.grall@xxxxxxx>> wrote:
On 22/08/2019 08:44, Wieczorkiewicz, Pawel wrote:
diff --git a/xen/include/xen/livepatch.h b/xen/include/xen/livepatch.h
index 2aec532ee2..a93126f631 100644
--- a/xen/include/xen/livepatch.h
+++ b/xen/include/xen/livepatch.h
@@ -117,7 +117,7 @@ int arch_livepatch_quiesce(void);
 void arch_livepatch_revive(void);
   void arch_livepatch_apply(struct livepatch_func *func);
-void arch_livepatch_revert(const struct livepatch_func *func);
+void arch_livepatch_revert(struct livepatch_func *func);

I doubt livepatch on Arm will compile after this change.

What would be you suggestion then?

Cross-compiler are nowadays widely available. So build testing your changes in common code would be the minimum.

I wish it was that simple. Nevertheless, I will try to prepare an environment to perform such builds.

Cross-compiling the hypervisor is really easy ;).

1) Download the cross-compiler tarball (here one [1]) and uncompress it. You can also install the one provided by your distro.

2) Build Xen hypervisor. Here an example for arm64:

42sh> cd xen.git/xen
42sh> make XEN_TARGET_ARCH=arm64 CROSS_COMPILER=<triplet>-

In my case, I am using the Arm toolchain AArch64 GNU/Linux target (aarch64-linux-gnu). So the <triplet> would be aarch64-linux-gnu.

This is assuming you have the compilers binary in your PATH. If not, you can use give the full path:


In this case, as you dropped the const from the prototype, you will need to do the same in the declaration.

Yes, but I see 2 options here:
- Enable the feature also for Arm (I prefer that, but will not be able to test that in nearest future)

I think some of the code can be made common. So we could possibly rely on x86 for that. Additionally, IIRC, Konrad has a setup on the cubietruck for testing livepatch.

- Keep Arm excluded and sprinkle code with #ifdef CONFIG_X86

Please no #ifdef CONFIG_X86 in the common code. If you don't plan to support Arm, then we should introduce a new Kconfig that will gate all those changes.


[1] https://developer.arm.com/tools-and-software/open-source-software/developer-tools/gnu-toolchain/gnu-a/downloads

Julien Grall

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