write_guest_abs(9)

📦 version 7.3.1, in nixpkgs unstable

💅 write_guest_abs(9) — the Kernel API Manual page, but make it make sense

okay so bestie, welcome to write_guest_abs(9) from the Kernel API Manual ✨ this is the little s390 KVM helper that yeets bytes from kernel space straight into guest space, absolute style. no cap, it's a whole vibe.

🌸 NAME 🌸

write_guest_abs — copy data from kernel space to guest space absolute 🫶

✨ SYNOPSIS ✨

int write_guest_abs (struct kvm_vcpu *vcpu , unsigned long gpa , void
*data , unsigned long len );

look at her. iconic signature. 💅

🎀 ARGUMENTS 🎀

  • vcpu — the virtual cpu, your main character 🧚
  • gpa — the guest physical (absolute) address, aka where in guest-land we're dropping the data 📍
  • data — the source address, in kernel space, aka where the data is coming from 💜
  • len — the number of bytes to copy, the actual amount, fr fr 🌸

🦋 DESCRIPTION 🦋

So what she does: copies len bytes from data (kernel space) over to gpa (that guest absolute address). Simple. Elegant. Slay. ✨

⚠️ but listen — it is up to the caller to make sure that the entire guest memory range is actually valid memory before calling this function. that's on you, bestie. not her job. 💀

Also lowkey important: guest low address and key protection are not checked. like, at all. not even a little. 🙈

Returns zero on success, or -EFAULT on error. that's the whole return situation, periodt. 👑

And the caveat you need to keep in your notes app: if an error occurs, data may have been copied partially to guest memory. partial. so like, half the vibe got through. handle it. 😭

🌈 SEE ALSO 🌈

Kernel file ./arch/s390/kvm/s390/gaccess.h — go read it, iykyk 💖

the whole guest-access friend group honestly, they all ate 🔥

mwah 💋 this page lives in ./arch/s390/kvm/s390, dated October 2026 — that's the source and the date, and yes she's serving vintage-adjacent. go copy some bytes responsibly, bestie. 🎀✨

📦 where this page comes from