linux-kernel - [PATCH] kvm: selftests: Fix cut-off of addr

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Date:   Wed, 13 Apr 2022 21:07:03 -0400
From:   Peter Xu <peterx@...hat.com>
To:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Ben Gardon <bgardon@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        David Matlack <dmatlack@...gle.com>, peterx@...hat.com,
        Sean Christopherson <seanjc@...gle.com>,
        Andrew Jones <drjones@...hat.com>
Subject: [PATCH] kvm: selftests: Fix cut-off of addr_gva2gpa lookup

Our QE team reported test failure on access_tracking_perf_test:

Testing guest mode: PA-bits:ANY, VA-bits:48,  4K pages
guest physical test memory offset: 0x3fffbffff000

Populating memory             : 0.684014577s
Writing to populated memory   : 0.006230175s
Reading from populated memory : 0.004557805s
==== Test Assertion Failure ====
  lib/kvm_util.c:1411: false
  pid=125806 tid=125809 errno=4 - Interrupted system call
     1  0x0000000000402f7c: addr_gpa2hva at kvm_util.c:1411
     2   (inlined by) addr_gpa2hva at kvm_util.c:1405
     3  0x0000000000401f52: lookup_pfn at access_tracking_perf_test.c:98
     4   (inlined by) mark_vcpu_memory_idle at access_tracking_perf_test.c:152
     5   (inlined by) vcpu_thread_main at access_tracking_perf_test.c:232
     6  0x00007fefe9ff81ce: ?? ??:0
     7  0x00007fefe9c64d82: ?? ??:0
  No vm physical memory at 0xffbffff000

And I can easily reproduce it with a Intel(R) Xeon(R) CPU E5-2630 with 46
bits PA.

It turns out that the address translation for clearing idle page tracking
returned wrong result, in which addr_gva2gpa()'s last step should have
treated "pte[index[0]].pfn" to be a 32bit value.  In above case the GPA
address 0x3fffbffff000 got cut-off into 0xffbffff000, then it caused
further lookup failure in the gpa2hva mapping.

I didn't yet check any other test that may fail too on some hosts, but
logically any test using addr_gva2gpa() could suffer.

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2075036
Signed-off-by: Peter Xu <peterx@...hat.com>
---
 tools/testing/selftests/kvm/lib/x86_64/processor.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/kvm/lib/x86_64/processor.c b/tools/testing/selftests/kvm/lib/x86_64/processor.c
index 9f000dfb5594..6c356fb4a9bf 100644
--- a/tools/testing/selftests/kvm/lib/x86_64/processor.c
+++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c
@@ -587,7 +587,7 @@ vm_paddr_t addr_gva2gpa(struct kvm_vm *vm, vm_vaddr_t gva)
 	if (!pte[index[0]].present)
 		goto unmapped_gva;
 
-	return (pte[index[0]].pfn * vm->page_size) + (gva & 0xfffu);
+	return ((vm_paddr_t)pte[index[0]].pfn * vm->page_size) + (gva & 0xfffu);
 
 unmapped_gva:
 	TEST_FAIL("No mapping for vm virtual address, gva: 0x%lx", gva);
-- 
2.32.0