linux-kernel - linux-next: KVM/s390x regression (was: [v7 03/16] mm/huge_memory: add device-private THP support to PMD operations)

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Message-ID: <20251017144924.10034-1-borntraeger@linux.ibm.com>
Date: Fri, 17 Oct 2025 16:49:24 +0200
From: Christian Borntraeger <borntraeger@...ux.ibm.com>
To: balbirs@...dia.com
Cc: Liam.Howlett@...cle.com, airlied@...il.com, akpm@...ux-foundation.org,
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        kvm@...r.kernel.org, linux-s390@...r.kernel.org,
        linux-next@...r.kernel.org
Subject: linux-next: KVM/s390x regression (was: [v7 03/16] mm/huge_memory: add device-private THP support to PMD operations)

This patch triggers a regression for s390x kvm as qemu guests can no longer start

error: kvm run failed Cannot allocate memory
PSW=mask 0000000180000000 addr 000000007fd00600
R00=0000000000000000 R01=0000000000000000 R02=0000000000000000 R03=0000000000000000
R04=0000000000000000 R05=0000000000000000 R06=0000000000000000 R07=0000000000000000
R08=0000000000000000 R09=0000000000000000 R10=0000000000000000 R11=0000000000000000
R12=0000000000000000 R13=0000000000000000 R14=0000000000000000 R15=0000000000000000
C00=00000000000000e0 C01=0000000000000000 C02=0000000000000000 C03=0000000000000000
C04=0000000000000000 C05=0000000000000000 C06=0000000000000000 C07=0000000000000000
C08=0000000000000000 C09=0000000000000000 C10=0000000000000000 C11=0000000000000000
C12=0000000000000000 C13=0000000000000000 C14=00000000c2000000 C15=0000000000000000

KVM on s390x does not use THP so far, will investigate. Does anyone have a quick idea?

Christian Borntraeger