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KVM: selftests: Tighten checks around prev iter's last dirty page in ring

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Now that each iteration collects all dirty entries and ensures the guest
*completes* at least one write, tighten the exemptions for the last dirty
page of the previous iteration.  Specifically, the only legal value (other
than the current iteration) is N-1.

Unlike the last page for the current iteration, the in-progress write from
the previous iteration is guaranteed to have completed, otherwise the test
would have hung.

Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Link: https://lore.kernel.org/r/20250111003004.1235645-18-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson 2025-01-10 16:30:01 -08:00
parent 73eaa2aa14
commit 2020d3b77a
1 changed files with 15 additions and 7 deletions
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22
tools/testing/selftests/kvm/dirty_log_test.c
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@ -517,14 +517,22 @@ static void vm_dirty_log_verify(enum vm_guest_mode mode, unsigned long **bmap)
if (host_log_mode == LOG_MODE_DIRTY_RING) {
/*
* The last page in the ring from this iteration
* or the previous can be written with the value
* from the previous iteration (relative to the
* last page's iteration), as the value to be
* written may be cached in a CPU register.
* The last page in the ring from previous
* iteration can be written with the value
* from the previous iteration, as the value to
* be written may be cached in a CPU register.
*/
if ((page == dirty_ring_last_page ||
page == dirty_ring_prev_iteration_last_page) &&
if (page == dirty_ring_prev_iteration_last_page &&
val == iteration - 1)
continue;
/*
* Any value from a previous iteration is legal
* for the last entry, as the write may not yet
* have retired, i.e. the page may hold whatever
* it had before this iteration started.
*/
if (page == dirty_ring_last_page &&
val < iteration)
continue;
} else if (!val && iteration == 1 && bmap0_dirty) {