[PATCH 0/2] selftests/kvm: Fixes for demand paging test

[PATCH 0/2] selftests/kvm: Fixes for demand paging test

[Peter Xu]

Two trivial fixes per subject, please see each patch, thanks.

Peter Xu (2):
  selftests/kvm: Setup vcpu_alias only for minor mode test
  selftests/kvm: Allow dump per-vcpu info for uffd threads

 .../testing/selftests/kvm/demand_paging_test.c  | 17 +++++++++--------
 .../selftests/kvm/lib/userfaultfd_util.c        |  4 ++--
 2 files changed, 11 insertions(+), 10 deletions(-)

-- 
2.39.1

[PATCH 1/2] selftests/kvm: Setup vcpu_alias only for minor mode test

[Peter Xu]

This fixes two things:

- Unbreaks MISSING mode test on anonymous memory type

- Prefault alias mem before uffd thread creations, otherwise the uffd
  thread timing will be inaccurate when guest mem size is large, because
  it'll take prefault time into total time.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 .../testing/selftests/kvm/demand_paging_test.c  | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/tools/testing/selftests/kvm/demand_paging_test.c b/tools/testing/selftests/kvm/demand_paging_test.c
index 2439c4043fed..9c18686b4f63 100644
--- a/tools/testing/selftests/kvm/demand_paging_test.c
+++ b/tools/testing/selftests/kvm/demand_paging_test.c
@@ -128,6 +128,7 @@ static void prefault_mem(void *alias, uint64_t len)
 
 static void run_test(enum vm_guest_mode mode, void *arg)
 {
+	struct memstress_vcpu_args *vcpu_args;
 	struct test_params *p = arg;
 	struct uffd_desc **uffd_descs = NULL;
 	struct timespec start;
@@ -145,24 +146,24 @@ static void run_test(enum vm_guest_mode mode, void *arg)
 		    "Failed to allocate buffer for guest data pattern");
 	memset(guest_data_prototype, 0xAB, demand_paging_size);
 
+	if (p->uffd_mode == UFFDIO_REGISTER_MODE_MINOR) {
+		for (i = 0; i < nr_vcpus; i++) {
+			vcpu_args = &memstress_args.vcpu_args[i];
+			prefault_mem(addr_gpa2alias(vm, vcpu_args->gpa),
+				     vcpu_args->pages * memstress_args.guest_page_size);
+		}
+	}
+
 	if (p->uffd_mode) {
 		uffd_descs = malloc(nr_vcpus * sizeof(struct uffd_desc *));
 		TEST_ASSERT(uffd_descs, "Memory allocation failed");
-
 		for (i = 0; i < nr_vcpus; i++) {
-			struct memstress_vcpu_args *vcpu_args;
 			void *vcpu_hva;
-			void *vcpu_alias;
 
 			vcpu_args = &memstress_args.vcpu_args[i];
 
 			/* Cache the host addresses of the region */
 			vcpu_hva = addr_gpa2hva(vm, vcpu_args->gpa);
-			vcpu_alias = addr_gpa2alias(vm, vcpu_args->gpa);
-
-			prefault_mem(vcpu_alias,
-				vcpu_args->pages * memstress_args.guest_page_size);
-
 			/*
 			 * Set up user fault fd to handle demand paging
 			 * requests.
-- 
2.39.1

[PATCH 2/2] selftests/kvm: Allow dump per-vcpu info for uffd threads

[Peter Xu]

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 <peterx@redhat.com>
---
 tools/testing/selftests/kvm/lib/userfaultfd_util.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/kvm/lib/userfaultfd_util.c b/tools/testing/selftests/kvm/lib/userfaultfd_util.c
index 92cef20902f1..271f63891581 100644
--- a/tools/testing/selftests/kvm/lib/userfaultfd_util.c
+++ b/tools/testing/selftests/kvm/lib/userfaultfd_util.c
@@ -70,7 +70,7 @@ static void *uffd_handler_thread_fn(void *arg)
 			r = read(pollfd[1].fd, &tmp_chr, 1);
 			TEST_ASSERT(r == 1,
 				    "Error reading pipefd in UFFD thread\n");
-			return NULL;
+			break;
 		}
 
 		if (!(pollfd[0].revents & POLLIN))
@@ -103,7 +103,7 @@ static void *uffd_handler_thread_fn(void *arg)
 	ts_diff = timespec_elapsed(start);
 	PER_VCPU_DEBUG("userfaulted %ld pages over %ld.%.9lds. (%f/sec)\n",
 		       pages, ts_diff.tv_sec, ts_diff.tv_nsec,
-		       pages / ((double)ts_diff.tv_sec + (double)ts_diff.tv_nsec / 100000000.0));
+		       pages / ((double)ts_diff.tv_sec + (double)ts_diff.tv_nsec / NSEC_PER_SEC));
 
 	return NULL;
 }
-- 
2.39.1

Re: [PATCH 2/2] selftests/kvm: Allow dump per-vcpu info for uffd threads

[James Houghton]

On Thu, Apr 27, 2023 at 1:11 PM Peter Xu <peterx@redhat.com> wrote:
>
> 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 <peterx@redhat.com>

Reviewed-by: James Houghton <jthoughton@google.com>

> ---
>  tools/testing/selftests/kvm/lib/userfaultfd_util.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/lib/userfaultfd_util.c b/tools/testing/selftests/kvm/lib/userfaultfd_util.c
> index 92cef20902f1..271f63891581 100644
> --- a/tools/testing/selftests/kvm/lib/userfaultfd_util.c
> +++ b/tools/testing/selftests/kvm/lib/userfaultfd_util.c
> @@ -70,7 +70,7 @@ static void *uffd_handler_thread_fn(void *arg)
>                         r = read(pollfd[1].fd, &tmp_chr, 1);
>                         TEST_ASSERT(r == 1,
>                                     "Error reading pipefd in UFFD thread\n");
> -                       return NULL;
> +                       break;
>                 }
>
>                 if (!(pollfd[0].revents & POLLIN))
> @@ -103,7 +103,7 @@ static void *uffd_handler_thread_fn(void *arg)
>         ts_diff = timespec_elapsed(start);
>         PER_VCPU_DEBUG("userfaulted %ld pages over %ld.%.9lds. (%f/sec)\n",
>                        pages, ts_diff.tv_sec, ts_diff.tv_nsec,
> -                      pages / ((double)ts_diff.tv_sec + (double)ts_diff.tv_nsec / 100000000.0));
> +                      pages / ((double)ts_diff.tv_sec + (double)ts_diff.tv_nsec / NSEC_PER_SEC));

I almost confused this fix for [1]. Thanks for catching this!

[1]: https://lore.kernel.org/kvm/20230223001805.2971237-1-amoorthy@google.com/

>
>         return NULL;
>  }
> --
> 2.39.1
>

Re: [PATCH 1/2] selftests/kvm: Setup vcpu_alias only for minor mode test

[James Houghton]

On Thu, Apr 27, 2023 at 1:11 PM Peter Xu <peterx@redhat.com> wrote:
>
> This fixes two things:
>
> - Unbreaks MISSING mode test on anonymous memory type
>
> - Prefault alias mem before uffd thread creations, otherwise the uffd
>   thread timing will be inaccurate when guest mem size is large, because
>   it'll take prefault time into total time.
>
> Signed-off-by: Peter Xu <peterx@redhat.com>

Reviewed-by: James Houghton <jthoughton@google.com>

FWIW, it looks like this fixes this commit[1]. Not sure if it's worth
a Fixes: tag.

[1]: commit a93871d0ea9f ("KVM: selftests: Add a userfaultfd library")


> ---
>  .../testing/selftests/kvm/demand_paging_test.c  | 17 +++++++++--------
>  1 file changed, 9 insertions(+), 8 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/demand_paging_test.c b/tools/testing/selftests/kvm/demand_paging_test.c
> index 2439c4043fed..9c18686b4f63 100644
> --- a/tools/testing/selftests/kvm/demand_paging_test.c
> +++ b/tools/testing/selftests/kvm/demand_paging_test.c
> @@ -128,6 +128,7 @@ static void prefault_mem(void *alias, uint64_t len)
>
>  static void run_test(enum vm_guest_mode mode, void *arg)
>  {
> +       struct memstress_vcpu_args *vcpu_args;
>         struct test_params *p = arg;
>         struct uffd_desc **uffd_descs = NULL;
>         struct timespec start;
> @@ -145,24 +146,24 @@ static void run_test(enum vm_guest_mode mode, void *arg)
>                     "Failed to allocate buffer for guest data pattern");
>         memset(guest_data_prototype, 0xAB, demand_paging_size);
>
> +       if (p->uffd_mode == UFFDIO_REGISTER_MODE_MINOR) {
> +               for (i = 0; i < nr_vcpus; i++) {
> +                       vcpu_args = &memstress_args.vcpu_args[i];
> +                       prefault_mem(addr_gpa2alias(vm, vcpu_args->gpa),
> +                                    vcpu_args->pages * memstress_args.guest_page_size);
> +               }
> +       }
> +
>         if (p->uffd_mode) {
>                 uffd_descs = malloc(nr_vcpus * sizeof(struct uffd_desc *));
>                 TEST_ASSERT(uffd_descs, "Memory allocation failed");
> -
>                 for (i = 0; i < nr_vcpus; i++) {
> -                       struct memstress_vcpu_args *vcpu_args;
>                         void *vcpu_hva;
> -                       void *vcpu_alias;
>
>                         vcpu_args = &memstress_args.vcpu_args[i];
>
>                         /* Cache the host addresses of the region */
>                         vcpu_hva = addr_gpa2hva(vm, vcpu_args->gpa);
> -                       vcpu_alias = addr_gpa2alias(vm, vcpu_args->gpa);
> -
> -                       prefault_mem(vcpu_alias,
> -                               vcpu_args->pages * memstress_args.guest_page_size);
> -
>                         /*
>                          * Set up user fault fd to handle demand paging
>                          * requests.
> --
> 2.39.1
>

Re: [PATCH 0/2] selftests/kvm: Fixes for demand paging test

[Sean Christopherson]

On Thu, 27 Apr 2023 16:11:10 -0400, Peter Xu wrote:
> Two trivial fixes per subject, please see each patch, thanks.
> 
> Peter Xu (2):
>   selftests/kvm: Setup vcpu_alias only for minor mode test
>   selftests/kvm: Allow dump per-vcpu info for uffd threads
> 
> .../testing/selftests/kvm/demand_paging_test.c  | 17 +++++++++--------
>  .../selftests/kvm/lib/userfaultfd_util.c        |  4 ++--
>  2 files changed, 11 insertions(+), 10 deletions(-)
> 
> [...]

Applied to kvm-x86 selftests, thanks!

[1/2] selftests/kvm: Setup vcpu_alias only for minor mode test
      https://github.com/kvm-x86/linux/commit/ba125de35da5
[2/2] selftests/kvm: Allow dump per-vcpu info for uffd threads
      https://github.com/kvm-x86/linux/commit/21912a653d7d

--
https://github.com/kvm-x86/linux/tree/next
https://github.com/kvm-x86/linux/tree/fixes