[PATCH 00/20] KVM: selftests: Fixes and cleanups for dirty_log_test

Sean Christopherson
2024-12-14T01:07:24Z

Fix a variety of flaws and false failures/passes in dirty_log_test, and
drop code/behavior that adds complexity while adding little-to-no benefit.

Lots of details in the changelogs, and a partial list of complaints[1] in
Maxim's original thread[2].

E.g. while not a particular interesting bug, hacking KVM like so doesn't
elicit a test failure.

---
include/linux/kvm_host.h | 2 ++
virt/kvm/kvm_main.c | 5 +++++
2 files changed, 7 insertions(+)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 401439bb21e3..bf7797ae2cdc 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -389,6 +389,8 @@ struct kvm_vcpu {
*/
struct kvm_memory_slot *last_used_slot;
u64 last_used_slot_gen;
+
+ bool extra_dirty;
};

/*
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index de2c11dae231..9981f1cc2780 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3444,6 +3444,11 @@ void mark_page_dirty_in_slot(struct kvm *kvm,
unsigned long rel_gfn = gfn - memslot->base_gfn;
u32 slot = (memslot->as_id << 16) | memslot->id;

+ if (!vcpu->extra_dirty &&
+ gfn_to_memslot(kvm, gfn + 1) == gfn) {
+ vcpu->extra_dirty = true;
+ mark_page_dirty_in_slot(kvm, memslot, gfn + 1);
+ }
if (kvm->dirty_ring_size && vcpu)
kvm_dirty_ring_push(vcpu, slot, rel_gfn);
else if (memslot->dirty_bitmap)
--

[1] https://lore.kernel.org/all/Z1vR25ylN5m_DRSy@google.com
[2] https://lore.kernel.org/all/20241211193706.469817-1-mlevitsk@redhat.com

Maxim Levitsky (2):
KVM: selftests: Support multiple write retires in dirty_log_test
KVM: selftests: Limit dirty_log_test's s390x workaround to s390x

Sean Christopherson (18):
KVM: selftests: Sync dirty_log_test iteration to guest *before*
resuming
KVM: selftests: Drop signal/kick from dirty ring testcase
KVM: selftests: Drop stale srandom() initialization from
dirty_log_test
KVM: selftests: Precisely track number of dirty/clear pages for each
iteration
KVM: selftests: Read per-page value into local var when verifying
dirty_log_test
KVM: selftests: Continuously reap dirty ring while vCPU is running
KVM: selftests: Honor "stop" request in dirty ring test
KVM: selftests: Keep dirty_log_test vCPU in guest until it needs to
stop
KVM: selftests: Post to sem_vcpu_stop if and only if vcpu_stop is true
KVM: selftests: Use continue to handle all "pass" scenarios in
dirty_log_test
KVM: selftests: Print (previous) last_page on dirty page value
mismatch
KVM: selftests: Collect *all* dirty entries in each dirty_log_test
iteration
KVM: sefltests: Verify value of dirty_log_test last page isn't bogus
KVM: selftests: Ensure guest writes min number of pages in
dirty_log_test
KVM: selftests: Tighten checks around prev iter's last dirty page in
ring
KVM: selftests: Set per-iteration variables at the start of each
iteration
KVM: selftests: Fix an off-by-one in the number of dirty_log_test
iterations
KVM: selftests: Allow running a single iteration of dirty_log_test

tools/testing/selftests/kvm/dirty_log_test.c | 515 +++++++++----------
1 file changed, 240 insertions(+), 275 deletions(-)

base-commit: fac04efc5c793dccbd07e2d59af9f90b7fc0dca4
--
2.47.1.613.gc27f4b7a9f-goog