kvm_s390_gisc_register(9)

💅 kvm_s390_gisc_register(9) 💅

okay so bestie, welcome to the Kernel API Manual ✨ — yes we're deep in the kernel, yes it's s390 flavoured, and yes this page is basically the origin story of registering a guest ISC. buckle up 🎀

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🌸 NAME 🌸

kvm_s390_gisc_register — register a guest ISC. that's it, that's the function, she's iconic and she does exactly one (1) thing 💖

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🦋 SYNOPSIS 🦋

int kvm_s390_gisc_register (struct kvm *kvm , u32 gisc );

literally the whole signature, no cap. kvm and gisc, that's the cast of the show 🔥

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🎀 ARGUMENTS 🎀

• kvm — the kernel vm you wanna work with 🫶 your main character, the vm in question.
• gisc — the guest interruption sub class you're registering 💫 yes it's a u32, yes it matters.

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⭐ DESCRIPTION ⭐

okay so here's the tea ☕ — this function extends the vm specific alert mask to use. that's the vibe, that's the job.

and like, the effective IAM mask in the GISA gets updated too — but only in the case where the GISA is not part of the GIB alert list 👀. if it's already part of the list, no update needed, we move on, we don't do extra work.

worst case scenario? it will be updated latest when the IAM gets restored by gisa_get_ipm_or_restore_iam 💅 so either way it lands, just maybe not right this second, iykyk.

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💜 RETURN 💜

so what do you get back, bestie? 🥁

• the nonspecific ISC (NISC) that the gib alert mechanism has registered with the channel subsystem ✨ that's the good ending, that's the win.
• -ENODEV — in case the vm uses no GISA 😭 like, there's no GISA to speak of, so, yeah.
• -ERANGE — in case the guest ISC is invalid 💀 range error, the ISC did not pass the vibe check.

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🌈 SEE ALSO 🌈

• Kernel file ./arch/s390/kvm/s390/interrupt.c
• gisa_set_iam(9)
• gisa_clear_ipm(9)
• gisa_get_ipm_or_restore_iam(9)
• kvm_s390_gisc_unregister(9) — the reverse bestie, go say hi 🦋

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ngl, if you're reading this page you're probably in the middle of some deeply s390 interrupt machinery, and honestly? respect. go off, queen 👑

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and that's the page, periodt 🎀 this gem lives under ./arch/s390/kvm/s390, and she's dated October 2026 — mark your calendars bestie, this manual page ate and left no crumbs ✨💖🌸