linux-kernel - [PATCH 2/5] KVM: selftests: Remove address rounding in guest code

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Message-Id: <20201027233733.1484855-3-bgardon@google.com>
Date:   Tue, 27 Oct 2020 16:37:30 -0700
From:   Ben Gardon <bgardon@...gle.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-kselftest@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>, Peter Xu <peterx@...hat.com>,
        Andrew Jones <drjones@...hat.com>,
        Peter Shier <pshier@...gle.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Thomas Huth <thuth@...hat.com>,
        Peter Feiner <pfeiner@...gle.com>,
        Ben Gardon <bgardon@...gle.com>
Subject: [PATCH 2/5] KVM: selftests: Remove address rounding in guest code

Rounding the address the guest writes to a host page boundary
will only have an effect if the host page size is larger than the guest
page size, but in that case the guest write would still go to the same
host page. There's no reason to round the address down, so remove the
rounding to simplify the demand paging test.

This series was tested by running the following invocations on an Intel
Skylake machine:
dirty_log_perf_test -b 20m -i 100 -v 64
dirty_log_perf_test -b 20g -i 5 -v 4
dirty_log_perf_test -b 4g -i 5 -v 32
demand_paging_test -b 20m -v 64
demand_paging_test -b 20g -v 4
demand_paging_test -b 4g -v 32
All behaved as expected.

Signed-off-by: Ben Gardon <bgardon@...gle.com>
---
 tools/testing/selftests/kvm/include/perf_test_util.h | 1 -
 1 file changed, 1 deletion(-)

diff --git a/tools/testing/selftests/kvm/include/perf_test_util.h b/tools/testing/selftests/kvm/include/perf_test_util.h
index f71f0858a1f29..838f946700f0c 100644
--- a/tools/testing/selftests/kvm/include/perf_test_util.h
+++ b/tools/testing/selftests/kvm/include/perf_test_util.h
@@ -72,7 +72,6 @@ static void guest_code(uint32_t vcpu_id)
 	for (i = 0; i < pages; i++) {
 		uint64_t addr = gva + (i * perf_test_args.guest_page_size);
 
-		addr &= ~(perf_test_args.host_page_size - 1);
 		*(uint64_t *)addr = 0x0123456789ABCDEF;
 	}
 
-- 
2.29.0.rc2.309.g374f81d7ae-goog