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

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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 <amoorthy@google.com>
Acked-by: James Houghton <jthoughton@google.com>
Link: https://lore.kernel.org/r/20240215235405.368539-12-amoorthy@google.com
[sean: fix kernel style violations, use calloc() for arrays]
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Anish Moorthy
2024-02-15 23:54:02 +00:00
committed by Sean Christopherson
parent 2ca76c12c4
commit df4ec5aada
4 changed files with 132 additions and 45 deletions
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81
tools/testing/selftests/kvm/lib/userfaultfd_util.c
View File

@@ -27,10 +27,8 @@
static void *uffd_handler_thread_fn(void *arg)
{
struct uffd_desc *uffd_desc = (struct uffd_desc *)arg;
int uffd = uffd_desc->uffd;
int pipefd = uffd_desc->pipefds[0];
useconds_t delay = uffd_desc->delay;
struct uffd_reader_args *reader_args = (struct uffd_reader_args *)arg;
int uffd = reader_args->uffd;
int64_t pages = 0;
struct timespec start;
struct timespec ts_diff;
@@ -44,7 +42,7 @@ static void *uffd_handler_thread_fn(void *arg)
pollfd[0].fd = uffd;
pollfd[0].events = POLLIN;
pollfd[1].fd = pipefd;
pollfd[1].fd = reader_args->pipe;
pollfd[1].events = POLLIN;
r = poll(pollfd, 2, -1);
@@ -92,9 +90,9 @@ static void *uffd_handler_thread_fn(void *arg)
if (!(msg.event & UFFD_EVENT_PAGEFAULT))
continue;
if (delay)
usleep(delay);
r = uffd_desc->handler(uffd_desc->uffd_mode, uffd, &msg);
if (reader_args->delay)
usleep(reader_args->delay);
r = reader_args->handler(reader_args->uffd_mode, uffd, &msg);
if (r < 0)
return NULL;
pages++;
@@ -110,6 +108,7 @@ static void *uffd_handler_thread_fn(void *arg)
struct uffd_desc *uffd_setup_demand_paging(int uffd_mode, useconds_t delay,
void *hva, uint64_t len,
uint64_t num_readers,
uffd_handler_t handler)
{
struct uffd_desc *uffd_desc;
@@ -118,14 +117,25 @@ struct uffd_desc *uffd_setup_demand_paging(int uffd_mode, useconds_t delay,
struct uffdio_api uffdio_api;
struct uffdio_register uffdio_register;
uint64_t expected_ioctls = ((uint64_t) 1) << _UFFDIO_COPY;
int ret;
int ret, i;
PER_PAGE_DEBUG("Userfaultfd %s mode, faults resolved with %s\n",
is_minor ? "MINOR" : "MISSING",
is_minor ? "UFFDIO_CONINUE" : "UFFDIO_COPY");
uffd_desc = malloc(sizeof(struct uffd_desc));
TEST_ASSERT(uffd_desc, "malloc failed");
TEST_ASSERT(uffd_desc, "Failed to malloc uffd descriptor");
uffd_desc->pipefds = calloc(sizeof(int), num_readers);
TEST_ASSERT(uffd_desc->pipefds, "Failed to alloc pipes");
uffd_desc->readers = calloc(sizeof(pthread_t), num_readers);
TEST_ASSERT(uffd_desc->readers, "Failed to alloc reader threads");
uffd_desc->reader_args = calloc(sizeof(struct uffd_reader_args), num_readers);
TEST_ASSERT(uffd_desc->reader_args, "Failed to alloc reader_args");
uffd_desc->num_readers = num_readers;
/* In order to get minor faults, prefault via the alias. */
if (is_minor)
@@ -148,18 +158,28 @@ struct uffd_desc *uffd_setup_demand_paging(int uffd_mode, useconds_t delay,
TEST_ASSERT((uffdio_register.ioctls & expected_ioctls) ==
expected_ioctls, "missing userfaultfd ioctls");
ret = pipe2(uffd_desc->pipefds, O_CLOEXEC | O_NONBLOCK);
TEST_ASSERT(!ret, "Failed to set up pipefd");
uffd_desc->uffd_mode = uffd_mode;
uffd_desc->uffd = uffd;
uffd_desc->delay = delay;
uffd_desc->handler = handler;
pthread_create(&uffd_desc->thread, NULL, uffd_handler_thread_fn,
uffd_desc);
for (i = 0; i < uffd_desc->num_readers; ++i) {
int pipes[2];
PER_VCPU_DEBUG("Created uffd thread for HVA range [%p, %p)\n",
hva, hva + len);
ret = pipe2((int *) &pipes, O_CLOEXEC | O_NONBLOCK);
TEST_ASSERT(!ret, "Failed to set up pipefd %i for uffd_desc %p",
i, uffd_desc);
uffd_desc->pipefds[i] = pipes[1];
uffd_desc->reader_args[i].uffd_mode = uffd_mode;
uffd_desc->reader_args[i].uffd = uffd;
uffd_desc->reader_args[i].delay = delay;
uffd_desc->reader_args[i].handler = handler;
uffd_desc->reader_args[i].pipe = pipes[0];
pthread_create(&uffd_desc->readers[i], NULL, uffd_handler_thread_fn,
&uffd_desc->reader_args[i]);
PER_VCPU_DEBUG("Created uffd thread %i for HVA range [%p, %p)\n",
i, hva, hva + len);
}
return uffd_desc;
}
@@ -167,19 +187,26 @@ struct uffd_desc *uffd_setup_demand_paging(int uffd_mode, useconds_t delay,
void uffd_stop_demand_paging(struct uffd_desc *uffd)
{
char c = 0;
int ret;
int i;
ret = write(uffd->pipefds[1], &c, 1);
TEST_ASSERT(ret == 1, "Unable to write to pipefd");
for (i = 0; i < uffd->num_readers; ++i)
TEST_ASSERT(write(uffd->pipefds[i], &c, 1) == 1,
"Unable to write to pipefd %i for uffd_desc %p", i, uffd);
ret = pthread_join(uffd->thread, NULL);
TEST_ASSERT(ret == 0, "Pthread_join failed.");
for (i = 0; i < uffd->num_readers; ++i)
TEST_ASSERT(!pthread_join(uffd->readers[i], NULL),
"Pthread_join failed on reader %i for uffd_desc %p", i, uffd);
close(uffd->uffd);
close(uffd->pipefds[1]);
close(uffd->pipefds[0]);
for (i = 0; i < uffd->num_readers; ++i) {
close(uffd->pipefds[i]);
close(uffd->reader_args[i].pipe);
}
free(uffd->pipefds);
free(uffd->readers);
free(uffd->reader_args);
free(uffd);
}