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yan yan

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May 20, 2021, 7:40:23 AMMay 20
to gvisor-users
Dear Friend:
My name is Yan Yan. Recently, i am learning the gVisor code, but i cannot unstandand the function about the "CheckHostCompatible()". It is to compare if the restored feature is  a subset of the host feature set. If i remove these part to check host feature, what will happen ?

yours sincerely,
Yan Yan

Michael Pratt

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May 20, 2021, 10:38:13 AMMay 20
to yan yan, gvisor-users
Many applications use CPUID at startup to determine which features are available and select from various implementations. e.g., using an AVX-optimized memcpy implementation when AVX is available. These decisions are usually cached to avoid using CPUID in the fast path.

If we save this application's state and restore it on a new machine with fewer features (e.g., no AVX support), then these applications are likely to crash with #UD / SIGILL when they try to use unsupported features.

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