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krun: create context after loading the library #1695

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merged 1 commit into from
Mar 20, 2025
Merged

krun: create context after loading the library #1695

merged 1 commit into from
Mar 20, 2025

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slp
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@slp slp commented Mar 19, 2025

Newer versions of libkrun no longer link against libkrunfw (the library bundling the kernel) and, instead, they load it dynamically when creating the context.

This implies we need to call krun_create_ctx ealier, before switching namespaces, or libkrun won't be able to find libkrunfw.

@slp slp force-pushed the krun-create-ctx branch from 9938f91 to 4f080f3 Compare March 19, 2025 12:13
@slp slp mentioned this pull request Mar 19, 2025
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rhatdan
rhatdan approved these changes Mar 19, 2025
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LGTM
@giuseppe @flouthoc PTAL

flouthoc
flouthoc approved these changes Mar 19, 2025
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LGTM

@siteshwar
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siteshwar commented Mar 19, 2025 •
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You may want to remove this variable as its not used:

Error: COMPILER_WARNING (CWE-563): [#def1]
crun-1.20-build/crun-HEAD/src/libcrun/handlers/krun.c: scope_hint: In function 'libkrun_exec'
crun-1.20-build/crun-HEAD/src/libcrun/handlers/krun.c:90:11: warning[-Wunused-but-set-variable]: variable 'ctx_id' set but not used
#   90 |   int32_t ctx_id, ret;
#      |           ^~~~~~
#   88|     void *handle;
#   89|     uint32_t num_vcpus, ram_mib;
#   90|->   int32_t ctx_id, ret;
#   91|     cpu_set_t set;
#   92|

@slp slp force-pushed the krun-create-ctx branch from 4f080f3 to 7cfd931 Compare March 19, 2025 17:42
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slp commented Mar 19, 2025

You may want to remove this variable as its not used:

Error: COMPILER_WARNING (CWE-563): [#def1]
crun-1.20-build/crun-HEAD/src/libcrun/handlers/krun.c: scope_hint: In function 'libkrun_exec'
crun-1.20-build/crun-HEAD/src/libcrun/handlers/krun.c:90:11: warning[-Wunused-but-set-variable]: variable 'ctx_id' set but not used
#   90 |   int32_t ctx_id, ret;
#      |           ^~~~~~
#   88|     void *handle;
#   89|     uint32_t num_vcpus, ram_mib;
#   90|->   int32_t ctx_id, ret;
#   91|     cpu_set_t set;
#   92|

This wonderful warning has actually detected a bug. I was always using the same ctx_id for both krun and krun-sev. This works because they happen to return the same integer, but was wrong. I've just fixed it, thanks!

@siteshwar
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You may want to remove this variable as its not used:

Error: COMPILER_WARNING (CWE-563): [#def1]
crun-1.20-build/crun-HEAD/src/libcrun/handlers/krun.c: scope_hint: In function 'libkrun_exec'
crun-1.20-build/crun-HEAD/src/libcrun/handlers/krun.c:90:11: warning[-Wunused-but-set-variable]: variable 'ctx_id' set but not used
#   90 |   int32_t ctx_id, ret;
#      |           ^~~~~~
#   88|     void *handle;
#   89|     uint32_t num_vcpus, ram_mib;
#   90|->   int32_t ctx_id, ret;
#   91|     cpu_set_t set;
#   92|

This wonderful warning has actually detected a bug. I was always using the same ctx_id for both krun and krun-sev. This works because they happen to return the same integer, but was wrong. I've just fixed it, thanks!

No problems! In the future, please keep an eye on the osh-diff-scan check in the CI.

giuseppe
giuseppe reviewed Mar 20, 2025
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@slp slp force-pushed the krun-create-ctx branch 2 times, most recently from 3586302 to a80c2e4 Compare March 20, 2025 12:31
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Thanks!

LGTM

@giuseppe
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@eriksjolund PTAL, if you are fine with the new version, I'll merge it

eriksjolund
eriksjolund reviewed Mar 20, 2025
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src/libcrun/handlers/krun.c Outdated

krun_create_ctx = dlsym (handle, "krun_create_ctx");
if (krun_create_ctx == NULL)
return crun_make_error (err, 0, "could not find symbol in `libkrun.so`");
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libkrun.so might sometimes be libkrun-sev.so in the error message

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Would it be reasonable to remove the .so to avoid inferring we're talking about that specific library, or do we need it to point to the right library?

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I think we can just change the error message in the krun library, or something like that

@slp
krun: create context after loading the library
8675baf 
Newer versions of libkrun no longer link against libkrunfw (the
library bundling the kernel) and, instead, they load it dynamically
when creating the context.

This implies we need to call krun_create_ctx ealier, before
switching namespaces, or libkrun won't be able to find libkrunfw.

Signed-off-by: Sergio Lopez <[email protected]>
@slp slp force-pushed the krun-create-ctx branch from a80c2e4 to 8675baf Compare March 20, 2025 13:27
giuseppe
giuseppe approved these changes Mar 20, 2025
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LGTM

@eriksjolund
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lgtm

@giuseppe giuseppe merged commit 4284382 into containers:main Mar 20, 2025
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@giuseppe giuseppe giuseppe approved these changes

@rhatdan rhatdan rhatdan approved these changes

@flouthoc flouthoc flouthoc approved these changes

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@slp @siteshwar @giuseppe @eriksjolund @rhatdan @flouthoc