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Reply-To: Sean Christopherson <seanjc@google.com>
Date:   Tue, 13 Dec 2022 00:16:42 +0000
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Subject: [PATCH 03/14] KVM: selftests: Fix divide-by-zero bug in memslot_perf_test
From:   Sean Christopherson <seanjc@google.com>
To:     Paolo Bonzini <pbonzini@redhat.com>, Marc Zyngier <maz@kernel.org>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>
Cc:     James Morse <james.morse@arm.com>,
        Alexandru Elisei <alexandru.elisei@arm.com>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        Oliver Upton <oliver.upton@linux.dev>,
        Tom Rix <trix@redhat.com>, kvm@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev,
        kvmarm@lists.cs.columbia.edu, linux-riscv@lists.infradead.org,
        llvm@lists.linux.dev, linux-kernel@vger.kernel.org,
        Ricardo Koller <ricarkol@google.com>,
        Sean Christopherson <seanjc@google.com>,
        Aaron Lewis <aaronlewis@google.com>,
        Raghavendra Rao Ananta <rananta@google.com>
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Precedence: bulk

Check that the number of pages per slot is non-zero in get_max_slots()
prior to computing the remaining number of pages.  clang generates code
that uses an actual DIV for calculating the remaining, which causes a #DE
if the total number of pages is less than the number of slots.

  traps: memslot_perf_te[97611] trap divide error ip:4030c4 sp:7ffd18ae58f0
         error:0 in memslot_perf_test[401000+cb000]

Fixes: a69170c65acd ("KVM: selftests: memslot_perf_test: Report optimal memory slots")
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 tools/testing/selftests/kvm/memslot_perf_test.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tools/testing/selftests/kvm/memslot_perf_test.c b/tools/testing/selftests/kvm/memslot_perf_test.c
index e698306bf49d..e6587e193490 100644
--- a/tools/testing/selftests/kvm/memslot_perf_test.c
+++ b/tools/testing/selftests/kvm/memslot_perf_test.c
@@ -265,6 +265,9 @@ static uint64_t get_max_slots(struct vm_data *data, uint32_t host_page_size)
 	slots = data->nslots;
 	while (--slots > 1) {
 		pages_per_slot = mempages / slots;
+		if (!pages_per_slot)
+			continue;
+
 		rempages = mempages % pages_per_slot;
 		if (check_slot_pages(host_page_size, guest_page_size,
 				     pages_per_slot, rempages))
-- 
2.39.0.rc1.256.g54fd8350bd-goog