dat_test_age_gfn(9)

okay so welcome to the Kernel API Manual page for dat_test_age_gfn(9), bestie — this is the little function that checks if a guest memory range is out here looking young 👑✨

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🌸 NAME 🌸

dat_test_age_gfn — Test young. literally that’s the whole vibe check 💅

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✨ SYNOPSIS ✨

bool dat_test_age_gfn (union asce asce , gfn_t start , gfn_t end );

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🎀 ARGUMENTS 🎀

• asce — the ASCE whose address range is to be tested. yes bestie, this is the one getting examined 🔍
• start — the first guest frame of the range to check. starting point, main character energy ⭐
• end — the guest frame after the last in the range. note: it’s after the last, not the last itself — iykyk 🫶

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🔒 CONTEXT 🔒

called by KVM common code with the kvm mmu write lock held. so yeah — lock is held, context is giving very “know your lane” energy 💀

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💖 RETURN 💖

true if any page in the given range is young, otherwise false.

so it’s a little yes/no moment: any young page in the range? true 🦋 none? false 🎀

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👀 SEE ALSO 👀

the Kernel file ./arch/s390/kvm/gmap/dat.c is the spot, and you also gotta peek at:

• dat_crstep_xchg_atomic(9)
• dat_entry_walk(9)
• _dat_walk_gfn_range(9)
• dat_perform_essa(9)
• dat_set_cmma_bits(9)

all the linked besties, no cap 🌈

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xoxo, your kernel bestie 💖 — source/version: ./arch/s390/kvm/gmap, date: October 2026 🎀