KVM: selftests: Fix spelling mistake "UFFDIO_CONINUE" -> "UFFDIO_CONTINUE"

There is a spelling mistake in a PER_PAGE_DEBUG debug message. Fix it.

Signed-off-by: Colin Ian King <[email protected]

KVM: selftests: Fix spelling mistake "UFFDIO_CONINUE" -> "UFFDIO_CONTINUE"

There is a spelling mistake in a PER_PAGE_DEBUG debug message. Fix it.

Signed-off-by: Colin Ian King <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Sean Christopherson <[email protected]>

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KVM: selftests: Define _GNU_SOURCE for all selftests code

Define _GNU_SOURCE is the base CFLAGS instead of relying on selftests to
manually #define _GNU_SOURCE, which is repetitive and error prone.

KVM: selftests: Define _GNU_SOURCE for all selftests code

Define _GNU_SOURCE is the base CFLAGS instead of relying on selftests to
manually #define _GNU_SOURCE, which is repetitive and error prone. E.g.
kselftest_harness.h requires _GNU_SOURCE for asprintf(), but if a selftest
includes kvm_test_harness.h after stdio.h, the include guards result in
the effective version of stdio.h consumed by kvm_test_harness.h not
defining asprintf():

In file included from x86_64/fix_hypercall_test.c:12:
In file included from include/kvm_test_harness.h:11:
../kselftest_harness.h:1169:2: error: call to undeclared function
'asprintf'; ISO C99 and later do not support implicit function declarations
[-Wimplicit-function-declaration]
1169 | asprintf(&test_name, "%s%s%s.%s", f->name,
| ^

When including the rseq selftest's "library" code, #undef _GNU_SOURCE so
that rseq.c controls whether or not it wants to build with _GNU_SOURCE.

Reported-by: Muhammad Usama Anjum <[email protected]>
Acked-by: Claudio Imbrenda <[email protected]>
Acked-by: Oliver Upton <[email protected]>
Acked-by: Anup Patel <[email protected]>
Reviewed-by: Muhammad Usama Anjum <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Sean Christopherson <[email protected]>

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KVM: selftests: Use EPOLL in userfaultfd_util reader threads

With multiple reader threads POLLing a single UFFD, the demand paging test
suffers from the thundering herd problem: performance degrades

KVM: selftests: Use EPOLL in userfaultfd_util reader threads

With multiple reader threads POLLing a single UFFD, the demand paging test
suffers from the thundering herd problem: performance degrades as the
number of reader threads is increased. Solve this issue [1] by switching
the the polling mechanism to EPOLL + EPOLLEXCLUSIVE.

Also, change the error-handling convention of uffd_handler_thread_fn.
Instead of just printing errors and returning early from the polling
loop, check for them via TEST_ASSERT(). "return NULL" is reserved for a
successful exit from uffd_handler_thread_fn, i.e. one triggered by a
write to the exit pipe.

Performance samples generated by the command in [2] are given below.

Num Reader Threads, Paging Rate (POLL), Paging Rate (EPOLL)
1 249k 185k
2 201k 235k
4 186k 155k
16 150k 217k
32 89k 198k

[1] Single-vCPU performance does suffer somewhat.
[2] ./demand_paging_test -u MINOR -s shmem -v 4 -o -r <num readers>

Signed-off-by: Anish Moorthy <[email protected]>
Acked-by: James Houghton <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Sean Christopherson <[email protected]>

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KVM: selftests: Allow many vCPUs and reader threads per UFFD in demand paging test

At the moment, demand_paging_test does not support profiling/testing
multiple vCPU threads concurrently faulting on

KVM: selftests: Allow many vCPUs and reader threads per UFFD in demand paging test

At the moment, demand_paging_test does not support profiling/testing
multiple vCPU threads concurrently faulting on a single uffd because

(a) "-u" (run test in userfaultfd mode) creates a uffd for each vCPU's
region, so that each uffd services a single vCPU thread.
(b) "-u -o" (userfaultfd mode + overlapped vCPU memory accesses)
simply doesn't work: the test tries to register the same memory
to multiple uffds, causing an error.

Add support for many vcpus per uffd by
(1) Keeping "-u" behavior unchanged.
(2) Making "-u -a" create a single uffd for all of guest memory.
(3) Making "-u -o" implicitly pass "-a", solving the problem in (b).
In cases (2) and (3) all vCPU threads fault on a single uffd.

With potentially multiple vCPUs per UFFD, it makes sense to allow
configuring the number of reader threads per UFFD as well: add the "-r"
flag to do so.

Signed-off-by: Anish Moorthy <[email protected]>
Acked-by: James Houghton <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
[sean: fix kernel style violations, use calloc() for arrays]
Signed-off-by: Sean Christopherson <[email protected]>

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KVM: selftests: Remove redundant newlines

TEST_* functions append their own newline. Remove newlines from
TEST_* callsites to avoid extra newlines in output.

Signed-off-by: Andrew Jones <ajones@ven

KVM: selftests: Remove redundant newlines

TEST_* functions append their own newline. Remove newlines from
TEST_* callsites to avoid extra newlines in output.

Signed-off-by: Andrew Jones <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Sean Christopherson <[email protected]>

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KVM: selftests: Allow dumping per-vcpu info for uffd threads

There's one PER_VCPU_DEBUG in per-vcpu uffd threads but it's never hit.

Trigger that when quit in normal ways (kick pollfd[1]), meanwhil

KVM: selftests: Allow dumping per-vcpu info for uffd threads

There's one PER_VCPU_DEBUG in per-vcpu uffd threads but it's never hit.

Trigger that when quit in normal ways (kick pollfd[1]), meanwhile fix the
number of nanosec calculation.

Signed-off-by: Peter Xu <[email protected]>
Reviewed-by: James Houghton <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Sean Christopherson <[email protected]>

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KVM: selftests: Add a userfaultfd library

Move the generic userfaultfd code out of demand_paging_test.c into a
common library, userfaultfd_util. This library consists of a setup and a
stop function.

KVM: selftests: Add a userfaultfd library

Move the generic userfaultfd code out of demand_paging_test.c into a
common library, userfaultfd_util. This library consists of a setup and a
stop function. The setup function starts a thread for handling page
faults using the handler callback function. This setup returns a
uffd_desc object which is then used in the stop function (to wait and
destroy the threads).

Reviewed-by: Oliver Upton <[email protected]>
Reviewed-by: Ben Gardon <[email protected]>
Signed-off-by: Ricardo Koller <[email protected]>
Signed-off-by: Marc Zyngier <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

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