Currently the private_mem_conversions_test crashes if invoked with the
-n <num_vcpus> option without also specifying multiple memslots via -m.
This is because the current implementation assumes -m is specified and
always sets up the per-vCPU memory with a dedicated memslot for each
vCPU. When -m is not specified, the test skips setting up
memslots/memory for secondary vCPUs.
The current code does seem to try to handle using a single memslot for
multiple vCPUs in some places, e.g. the call-site, but
test_mem_conversions() is missing the important bit of sizing the single
memslot appropriately to handle all the per-vCPU memory. Implement that
handling.
Signed-off-by: Michael Roth <[email protected]>
---
.../kvm/x86_64/private_mem_conversions_test.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/tools/testing/selftests/kvm/x86_64/private_mem_conversions_test.c b/tools/testing/selftests/kvm/x86_64/private_mem_conversions_test.c
index c04e7d61a585..5eb693fead33 100644
--- a/tools/testing/selftests/kvm/x86_64/private_mem_conversions_test.c
+++ b/tools/testing/selftests/kvm/x86_64/private_mem_conversions_test.c
@@ -388,10 +388,14 @@ static void test_mem_conversions(enum vm_mem_backing_src_type src_type, uint32_t
gmem_flags = 0;
memfd = vm_create_guest_memfd(vm, memfd_size, gmem_flags);
- for (i = 0; i < nr_memslots; i++)
- vm_mem_add(vm, src_type, BASE_DATA_GPA + size * i,
- BASE_DATA_SLOT + i, size / vm->page_size,
- KVM_MEM_PRIVATE, memfd, size * i);
+ if (nr_memslots == 1)
+ vm_mem_add(vm, src_type, BASE_DATA_GPA, BASE_DATA_SLOT,
+ memfd_size / vm->page_size, KVM_MEM_PRIVATE, memfd, 0);
+ else
+ for (i = 0; i < nr_memslots; i++)
+ vm_mem_add(vm, src_type, BASE_DATA_GPA + size * i,
+ BASE_DATA_SLOT + i, size / vm->page_size,
+ KVM_MEM_PRIVATE, memfd, size * i);
for (i = 0; i < nr_vcpus; i++) {
uint64_t gpa = BASE_DATA_GPA + i * size;
--
2.25.1
On Mon, Oct 16, 2023, Michael Roth wrote:
> Currently the private_mem_conversions_test crashes if invoked with the
> -n <num_vcpus> option without also specifying multiple memslots via -m.
Totally a PEBKAC, not a bug ;-)
> This is because the current implementation assumes -m is specified and
> always sets up the per-vCPU memory with a dedicated memslot for each
> vCPU. When -m is not specified, the test skips setting up
> memslots/memory for secondary vCPUs.
>
> The current code does seem to try to handle using a single memslot for
> multiple vCPUs in some places, e.g. the call-site, but
> test_mem_conversions() is missing the important bit of sizing the single
> memslot appropriately to handle all the per-vCPU memory. Implement that
> handling.
>
> Signed-off-by: Michael Roth <[email protected]>
> ---
> .../kvm/x86_64/private_mem_conversions_test.c | 12 ++++++++----
> 1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/x86_64/private_mem_conversions_test.c b/tools/testing/selftests/kvm/x86_64/private_mem_conversions_test.c
> index c04e7d61a585..5eb693fead33 100644
> --- a/tools/testing/selftests/kvm/x86_64/private_mem_conversions_test.c
> +++ b/tools/testing/selftests/kvm/x86_64/private_mem_conversions_test.c
> @@ -388,10 +388,14 @@ static void test_mem_conversions(enum vm_mem_backing_src_type src_type, uint32_t
> gmem_flags = 0;
> memfd = vm_create_guest_memfd(vm, memfd_size, gmem_flags);
>
> - for (i = 0; i < nr_memslots; i++)
> - vm_mem_add(vm, src_type, BASE_DATA_GPA + size * i,
> - BASE_DATA_SLOT + i, size / vm->page_size,
> - KVM_MEM_PRIVATE, memfd, size * i);
> + if (nr_memslots == 1)
> + vm_mem_add(vm, src_type, BASE_DATA_GPA, BASE_DATA_SLOT,
> + memfd_size / vm->page_size, KVM_MEM_PRIVATE, memfd, 0);
> + else
> + for (i = 0; i < nr_memslots; i++)
The if-else needs curly braces.
> + vm_mem_add(vm, src_type, BASE_DATA_GPA + size * i,
> + BASE_DATA_SLOT + i, size / vm->page_size,
> + KVM_MEM_PRIVATE, memfd, size * i);
But I think that's a moot point, because isn't it easier to do this?
diff --git a/tools/testing/selftests/kvm/x86_64/private_mem_conversions_test.c b/tools/testing/selftests/kvm/x86_64/private_mem_conversions_test.c
index c04e7d61a585..c99073098f98 100644
--- a/tools/testing/selftests/kvm/x86_64/private_mem_conversions_test.c
+++ b/tools/testing/selftests/kvm/x86_64/private_mem_conversions_test.c
@@ -367,6 +367,7 @@ static void test_mem_conversions(enum vm_mem_backing_src_type src_type, uint32_t
*/
const size_t size = align_up(PER_CPU_DATA_SIZE, get_backing_src_pagesz(src_type));
const size_t memfd_size = size * nr_vcpus;
+ const size_t slot_size = memfd_size / nr_memslots;
struct kvm_vcpu *vcpus[KVM_MAX_VCPUS];
pthread_t threads[KVM_MAX_VCPUS];
uint64_t gmem_flags;
@@ -390,7 +391,7 @@ static void test_mem_conversions(enum vm_mem_backing_src_type src_type, uint32_t
for (i = 0; i < nr_memslots; i++)
vm_mem_add(vm, src_type, BASE_DATA_GPA + size * i,
- BASE_DATA_SLOT + i, size / vm->page_size,
+ BASE_DATA_SLOT + i, slot_size / vm->page_size,
KVM_MEM_PRIVATE, memfd, size * i);
for (i = 0; i < nr_vcpus; i++) {
On Tue, Oct 17, 2023, Sean Christopherson wrote:
> On Mon, Oct 16, 2023, Michael Roth wrote:
> > + vm_mem_add(vm, src_type, BASE_DATA_GPA + size * i,
> > + BASE_DATA_SLOT + i, size / vm->page_size,
> > + KVM_MEM_PRIVATE, memfd, size * i);
>
> But I think that's a moot point, because isn't it easier to do this?
>
> diff --git a/tools/testing/selftests/kvm/x86_64/private_mem_conversions_test.c b/tools/testing/selftests/kvm/x86_64/private_mem_conversions_test.c
> index c04e7d61a585..c99073098f98 100644
> --- a/tools/testing/selftests/kvm/x86_64/private_mem_conversions_test.c
> +++ b/tools/testing/selftests/kvm/x86_64/private_mem_conversions_test.c
> @@ -367,6 +367,7 @@ static void test_mem_conversions(enum vm_mem_backing_src_type src_type, uint32_t
> */
> const size_t size = align_up(PER_CPU_DATA_SIZE, get_backing_src_pagesz(src_type));
> const size_t memfd_size = size * nr_vcpus;
> + const size_t slot_size = memfd_size / nr_memslots;
> struct kvm_vcpu *vcpus[KVM_MAX_VCPUS];
> pthread_t threads[KVM_MAX_VCPUS];
> uint64_t gmem_flags;
> @@ -390,7 +391,7 @@ static void test_mem_conversions(enum vm_mem_backing_src_type src_type, uint32_t
>
> for (i = 0; i < nr_memslots; i++)
> vm_mem_add(vm, src_type, BASE_DATA_GPA + size * i,
> - BASE_DATA_SLOT + i, size / vm->page_size,
> + BASE_DATA_SLOT + i, slot_size / vm->page_size,
> KVM_MEM_PRIVATE, memfd, size * i);
This isn't quite right, the stride and offset needs to be per-memslot too. Argh,
I created quite the mess by trying to take a shortcut for testing multiple memslots,
i.e. by only allowing '1' or "nr_vcpus" memslots. Much of the code assumes that
ranges can't be covered by multiple memslots, e.g. the UCALL_SYNC handler assumes
the entire range is contiguous in the host virtual address space.
And I think there's meaningful coverage we're not getting, e.g. as is I don't think
we're testing KVM_SET_MEMORY_ATTRIBUTES across multiple memslots (thankfully we
seem to have gotten the KVM side of things correct).
I'll post a small series to clean up the mess and let the user specify the number
of memslots (with some restrictions to keep the code relatively simple).