[PATCH v7 7/8] KVM: selftests: Only warn for idle-page checks on powerpc pseries LPAR
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COOLING6d
IN LINUX-NEXT: 1 (0M)
From: "Ritesh Harjani (IBM)" <ritesh.list@gmail.com>
Date: 2026-10-06 10:30:22
Also in:
kvm, lkml
Subsystem:
kernel selftest framework, kernel virtual machine (kvm), the rest · Maintainers:
Shuah Khan, Shuah Khan, Paolo Bonzini, Linus Torvalds
Revision v7 of 4 in this series; 1 review trailer; queued in linux-next as e5983ef19a6a on 2026-10-13.
Revisions (4)
- v3 [diff vs current]
- v3 [diff vs current]
- v5 [diff vs current]
- v7 current
Same nested TLB/access bit issue like x86. PowerPC nested KVM (pSeries LPAR) can hide accessed/idle, since KVM (L1) doesn't explicitly flush the TLB for access bit update, so L0 keeps translations cached. That also means that the L2 accesses do not refault and L1 thinks that the pages for L2 memory are still idle. Use kvm_is_ppc_pseries_lpar() check to detect when running nested on powerpc pseries LPAR and only warn on the idle-page count. Reported-by: Anushree Mathur <redacted> Tested-by: Anushree Mathur <redacted> Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com> --- tools/testing/selftests/kvm/Makefile.kvm | 1 + .../testing/selftests/kvm/access_tracking_perf_test.c | 10 ++++++++++ 2 files changed, 11 insertions(+)
diff --git a/tools/testing/selftests/kvm/Makefile.kvm b/tools/testing/selftests/kvm/Makefile.kvm
index 4b7f6ab0ee54..692bbae44a65 100644
--- a/tools/testing/selftests/kvm/Makefile.kvm
+++ b/tools/testing/selftests/kvm/Makefile.kvm@@ -257,6 +257,7 @@ TEST_GEN_PROGS_loongarch += set_memory_region_test TEST_GEN_PROGS_loongarch += steal_time TEST_GEN_PROGS_powerpc = $(TEST_GEN_PROGS_COMMON) +TEST_GEN_PROGS_powerpc += access_tracking_perf_test SPLIT_TESTS += arch_timer SPLIT_TESTS += get-reg-list
diff --git a/tools/testing/selftests/kvm/access_tracking_perf_test.c b/tools/testing/selftests/kvm/access_tracking_perf_test.c
index 4415c94b2866..eb6939065e79 100644
--- a/tools/testing/selftests/kvm/access_tracking_perf_test.c
+++ b/tools/testing/selftests/kvm/access_tracking_perf_test.c@@ -471,6 +471,16 @@ static int access_tracking_unreliable(void) return 1; } #endif + /* + * PowerPC: Nested KVM (pSeries LPAR) can hide accessed/idle, since KVM + * doesn't explicitely flush the TLB for access bit update. L0 keeps + * translations cached so the guest won't see the idle bit cleared. + */ + if (kvm_is_ppc_pseries_lpar()) { + puts("Skipping idle page count sanity check, because the test is run nested"); + return 1; + } + /* * When NUMA balancing is enabled, guest memory will be unmapped to get * NUMA faults, dropping the Accessed bits.
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2.39.5