linux-stable.git/tools/testing/selftests/kvm, branch v6.0

KVM: selftests: Compare insn opcodes directly in fix_hypercall_test

2022-09-30T10:38:02+00:00

Directly compare the expected versus observed hypercall instructions when
verifying that KVM patched in the native hypercall (FIX_HYPERCALL_INSN
quirk enabled).  gcc rightly complains that doing a 4-byte memcpy() with
an "unsigned char" as the source generates an out-of-bounds accesses.

Alternatively, "exp" and "obs" could be declared as 3-byte arrays, but
there's no known reason to copy locally instead of comparing directly.

In function ‘assert_hypercall_insn’,
    inlined from ‘guest_main’ at x86_64/fix_hypercall_test.c:91:2:
x86_64/fix_hypercall_test.c:63:9: error: array subscript ‘unsigned int[0]’
 is partly outside array bounds of ‘unsigned char[1]’ [-Werror=array-bounds]
   63 |         memcpy(&exp, exp_insn, sizeof(exp));
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
x86_64/fix_hypercall_test.c: In function ‘guest_main’:
x86_64/fix_hypercall_test.c:42:22: note: object ‘vmx_hypercall_insn’ of size 1
   42 | extern unsigned char vmx_hypercall_insn;
      |                      ^~~~~~~~~~~~~~~~~~
x86_64/fix_hypercall_test.c:25:22: note: object ‘svm_hypercall_insn’ of size 1
   25 | extern unsigned char svm_hypercall_insn;
      |                      ^~~~~~~~~~~~~~~~~~
In function ‘assert_hypercall_insn’,
    inlined from ‘guest_main’ at x86_64/fix_hypercall_test.c:91:2:
x86_64/fix_hypercall_test.c:64:9: error: array subscript ‘unsigned int[0]’
 is partly outside array bounds of ‘unsigned char[1]’ [-Werror=array-bounds]
   64 |         memcpy(&obs, obs_insn, sizeof(obs));
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
x86_64/fix_hypercall_test.c: In function ‘guest_main’:
x86_64/fix_hypercall_test.c:25:22: note: object ‘svm_hypercall_insn’ of size 1
   25 | extern unsigned char svm_hypercall_insn;
      |                      ^~~~~~~~~~~~~~~~~~
x86_64/fix_hypercall_test.c:42:22: note: object ‘vmx_hypercall_insn’ of size 1
   42 | extern unsigned char vmx_hypercall_insn;
      |                      ^~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
make: *** [../lib.mk:135: tools/testing/selftests/kvm/x86_64/fix_hypercall_test] Error 1

Fixes: 6c2fa8b20d0c ("selftests: KVM: Test KVM_X86_QUIRK_FIX_HYPERCALL_INSN")
Cc: Oliver Upton 
Signed-off-by: Sean Christopherson 
Reviewed-by: Oliver Upton 
Message-Id: <20220928233652.783504-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini

KVM: selftests: Implement memcmp(), memcpy(), and memset() for guest use

2022-09-30T10:38:02+00:00

Implement memcmp(), memcpy(), and memset() to override the compiler's
built-in versions in order to guarantee that the compiler won't generate
out-of-line calls to external functions via the PLT.  This allows the
helpers to be safely used in guest code, as KVM selftests don't support
dynamic loading of guest code.

Steal the implementations from the kernel's generic versions, sans the
optimizations in memcmp() for unaligned accesses.

Put the utilities in a separate compilation unit and build with
-ffreestanding to fudge around a gcc "feature" where it will optimize
memset(), memcpy(), etc... by generating a recursive call.  I.e. the
compiler optimizes itself into infinite recursion.  Alternatively, the
individual functions could be tagged with
optimize("no-tree-loop-distribute-patterns"), but using "optimize" for
anything but debug is discouraged, and Linus NAK'd the use of the flag
in the kernel proper[*].

https://lore.kernel.org/lkml/CAHk-=wik-oXnUpfZ6Hw37uLykc-_P0Apyn2XuX-odh-3Nzop8w@mail.gmail.com

Cc: Andrew Jones 
Cc: Anup Patel 
Cc: Atish Patra 
Cc: Christian Borntraeger 
Cc: Janosch Frank 
Cc: Claudio Imbrenda 
Signed-off-by: Sean Christopherson 
Message-Id: <20220928233652.783504-2-seanjc@google.com>
Reviewed-by: Andrew Jones 
Signed-off-by: Paolo Bonzini

KVM: selftests: Gracefully handle empty stack traces

2022-09-30T10:38:00+00:00

Bail out of test_dump_stack() if the stack trace is empty rather than
invoking addr2line with zero addresses. The problem with the latter is
that addr2line will block waiting for addresses to be passed in via
stdin, e.g. if running a selftest from an interactive terminal.

Opportunistically fix up the comment that mentions skipping 3 frames
since only 2 are skipped in the code.

Cc: Vipin Sharma 
Cc: Sean Christopherson 
Signed-off-by: David Matlack 
Message-Id: <20220922231724.3560211-1-dmatlack@google.com>
[Small tweak to keep backtrace() call close to if(). - Paolo]
Signed-off-by: Paolo Bonzini

KVM: selftests: replace assertion with warning in access_tracking_perf_test

2022-09-30T10:38:00+00:00

Page_idle uses {ptep/pmdp}_clear_young_notify which in turn calls
the mmu notifier callback ->clear_young(), which purposefully
does not flush the TLB.

When running the test in a nested guest, point 1. of the test
doc header is violated, because KVM TLB is unbounded by size
and since no flush is forced, KVM does not update the sptes
accessed/idle bits resulting in guest assertion failure.

More precisely, only the first ACCESS_WRITE in run_test() actually
makes visible changes, because sptes are created and the accessed
bit is set to 1 (or idle bit is 0). Then the first mark_memory_idle()
passes since access bit is still one, and sets all pages as idle
(or not accessed). When the next write is performed, the update
is not flushed therefore idle is still 1 and next mark_memory_idle()
fails.

Signed-off-by: Emanuele Giuseppe Esposito 
Message-Id: <20220926082923.299554-1-eesposit@redhat.com>
Signed-off-by: Paolo Bonzini

KVM: selftests: Skip tests that require EPT when it is not available

2022-09-27T11:58:03+00:00

Skip selftests that require EPT support in the VM when it is not
available. For example, if running on a machine where kvm_intel.ept=N
since KVM does not offer EPT support to guests if EPT is not supported
on the host.

This commit causes vmx_dirty_log_test to be skipped instead of failing
on hosts where kvm_intel.ept=N.

Signed-off-by: David Matlack 
Message-Id: <20220926171457.532542-1-dmatlack@google.com>
Signed-off-by: Paolo Bonzini

selftests: kvm: Fix a compile error in selftests/kvm/rseq_test.c

2022-09-22T21:02:20+00:00

The following warning appears when executing:
	make -C tools/testing/selftests/kvm

rseq_test.c: In function ‘main’:
rseq_test.c:237:33: warning: implicit declaration of function ‘gettid’; did you mean ‘getgid’? [-Wimplicit-function-declaration]
          (void *)(unsigned long)gettid());
                                 ^~~~~~
                                 getgid
/usr/bin/ld: /tmp/ccr5mMko.o: in function `main':
../kvm/tools/testing/selftests/kvm/rseq_test.c:237: undefined reference to `gettid'
collect2: error: ld returned 1 exit status
make: *** [../lib.mk:173: ../kvm/tools/testing/selftests/kvm/rseq_test] Error 1

Use the more compatible syscall(SYS_gettid) instead of gettid() to fix it.
More subsequent reuse may cause it to be wrapped in a lib file.

Signed-off-by: Jinrong Liang 
Message-Id: <20220802071240.84626-1-cloudliang@tencent.com>
Signed-off-by: Paolo Bonzini

KVM: selftests: Fix ambiguous mov in KVM_ASM_SAFE()

2022-08-19T11:38:05+00:00

Change the mov in KVM_ASM_SAFE() that zeroes @vector to a movb to
make it unambiguous.

This fixes a build failure with Clang since, unlike the GNU assembler,
the LLVM integrated assembler rejects ambiguous X86 instructions that
don't have suffixes:

  In file included from x86_64/hyperv_features.c:13:
  include/x86_64/processor.h:825:9: error: ambiguous instructions require an explicit suffix (could be 'movb', 'movw', 'movl', or 'movq')
          return kvm_asm_safe("wrmsr", "a"(val & -1u), "d"(val >> 32), "c"(msr));
                 ^
  include/x86_64/processor.h:802:15: note: expanded from macro 'kvm_asm_safe'
          asm volatile(KVM_ASM_SAFE(insn)                 \
                       ^
  include/x86_64/processor.h:788:16: note: expanded from macro 'KVM_ASM_SAFE'
          "1: " insn "\n\t"                                       \
                        ^
  :5:2: note: instantiated into assembly here
          mov $0, 15(%rsp)
          ^

It seems like this change could introduce undesirable behavior in the
future, e.g. if someone used a type larger than a u8 for @vector, since
KVM_ASM_SAFE() will only zero the bottom byte. I tried changing the type
of @vector to an int to see what would happen. GCC failed to compile due
to a size mismatch between `movb` and `%eax`. Clang succeeded in
compiling, but the generated code looked correct, so perhaps it will not
be an issue. That being said it seems like there could be a better
solution to this issue that does not assume @vector is a u8.

Fixes: 3b23054cd3f5 ("KVM: selftests: Add x86-64 support for exception fixup")
Signed-off-by: David Matlack 
Reviewed-by: Sean Christopherson 
Message-Id: <20220722234838.2160385-3-dmatlack@google.com>
Signed-off-by: Paolo Bonzini

KVM: selftests: Fix KVM_EXCEPTION_MAGIC build with Clang

2022-08-19T11:38:05+00:00

Change KVM_EXCEPTION_MAGIC to use the all-caps "ULL", rather than lower
case. This fixes a build failure with Clang:

  In file included from x86_64/hyperv_features.c:13:
  include/x86_64/processor.h:825:9: error: unexpected token in argument list
          return kvm_asm_safe("wrmsr", "a"(val & -1u), "d"(val >> 32), "c"(msr));
                 ^
  include/x86_64/processor.h:802:15: note: expanded from macro 'kvm_asm_safe'
          asm volatile(KVM_ASM_SAFE(insn)                 \
                       ^
  include/x86_64/processor.h:785:2: note: expanded from macro 'KVM_ASM_SAFE'
          "mov $" __stringify(KVM_EXCEPTION_MAGIC) ", %%r9\n\t"   \
          ^
  :1:18: note: instantiated into assembly here
          mov $0xabacadabaull, %r9
                          ^

Fixes: 3b23054cd3f5 ("KVM: selftests: Add x86-64 support for exception fixup")
Signed-off-by: David Matlack 
Reviewed-by: Sean Christopherson 
Message-Id: <20220722234838.2160385-2-dmatlack@google.com>
Signed-off-by: Paolo Bonzini

KVM: selftests: Test all possible "invalid" PERF_CAPABILITIES.LBR_FMT vals

2022-08-10T19:08:29+00:00

Test all possible input values to verify that KVM rejects all values
except the exact host value.  Due to the LBR format affecting the core
functionality of LBRs, KVM can't emulate "other" formats, so even though
there are a variety of legal values, KVM should reject anything but an
exact host match.

Suggested-by: Like Xu 
Signed-off-by: Sean Christopherson 
Signed-off-by: Paolo Bonzini

KVM: selftests: Use getcpu() instead of sched_getcpu() in rseq_test

2022-08-10T19:08:29+00:00

sched_getcpu() is glibc dependent and it can simply return the CPU
ID from the registered rseq information, as Florian Weimer pointed.
In this case, it's pointless to compare the return value from
sched_getcpu() and that fetched from the registered rseq information.

Fix the issue by replacing sched_getcpu() with getcpu(), as Florian
suggested. The comments are modified accordingly by replacing
"sched_getcpu()" with "getcpu()".

Reported-by: Yihuang Yu 
Suggested-by: Florian Weimer 
Suggested-by: Mathieu Desnoyers 
Suggested-by: Sean Christopherson 
Signed-off-by: Gavin Shan 
Message-Id: <20220810104114.6838-3-gshan@redhat.com>
Signed-off-by: Paolo Bonzini