Re: [PATCH 3/3] selftests: kvm: Add support for customized slot0 memory size

[Andrew Jones <drjones@redhat.com>]

On Wed, Jun 09, 2021 at 07:38:16AM +0800, Zhenzhong Duan wrote:
> Current implementatiion only create VM with slot0 memory size
> of fixed 512 pages plus page tables and per-cpu memory.
> 
> Add a new parameter slot0_mem_pages to vm_create_with_vcpus() and
> some comments to clarify the meaning of slot0_mem_pages and
> extra_mem_pages.
> 
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
> ---
>  .../testing/selftests/kvm/include/kvm_util.h  |  7 +--
>  .../selftests/kvm/kvm_page_table_test.c       |  2 +-
>  tools/testing/selftests/kvm/lib/kvm_util.c    | 47 +++++++++++++++----
>  .../selftests/kvm/lib/perf_test_util.c        |  2 +-
>  4 files changed, 44 insertions(+), 14 deletions(-)
> 
> diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
> index fcd8e3855111..8bcadfa8cea5 100644
> --- a/tools/testing/selftests/kvm/include/kvm_util.h
> +++ b/tools/testing/selftests/kvm/include/kvm_util.h
> @@ -285,10 +285,11 @@ struct kvm_vm *vm_create_default_with_vcpus(uint32_t nr_vcpus, uint64_t extra_me
>  					    uint32_t num_percpu_pages, void *guest_code,
>  					    uint32_t vcpuids[]);
>  
> -/* Like vm_create_default_with_vcpus, but accepts mode as a parameter */
> +/* Like vm_create_default_with_vcpus, but accepts mode and slot0 memory as a parameter */
>  struct kvm_vm *vm_create_with_vcpus(enum vm_guest_mode mode, uint32_t nr_vcpus,
> -				    uint64_t extra_mem_pages, uint32_t num_percpu_pages,
> -				    void *guest_code, uint32_t vcpuids[]);
> +				    uint64_t slot0_mem_pages, uint64_t extra_mem_pages,
> +				    uint32_t num_percpu_pages, void *guest_code,
> +				    uint32_t vcpuids[]);
>  
>  /*
>   * Adds a vCPU with reasonable defaults (e.g. a stack)
> diff --git a/tools/testing/selftests/kvm/kvm_page_table_test.c b/tools/testing/selftests/kvm/kvm_page_table_test.c
> index 1c4753fff19e..82171f17c1d7 100644
> --- a/tools/testing/selftests/kvm/kvm_page_table_test.c
> +++ b/tools/testing/selftests/kvm/kvm_page_table_test.c
> @@ -268,7 +268,7 @@ static struct kvm_vm *pre_init_before_test(enum vm_guest_mode mode, void *arg)
>  
>  	/* Create a VM with enough guest pages */
>  	guest_num_pages = test_mem_size / guest_page_size;
> -	vm = vm_create_with_vcpus(mode, nr_vcpus,
> +	vm = vm_create_with_vcpus(mode, nr_vcpus, DEFAULT_GUEST_PHY_PAGES,
>  				  guest_num_pages, 0, guest_code, NULL);
>  
>  	/* Align down GPA of the testing memslot */
> diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
> index 63418df921f0..d86422a119fd 100644
> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> @@ -308,21 +308,50 @@ struct kvm_vm *vm_create(enum vm_guest_mode mode, uint64_t phy_pages, int perm)
>  	return vm;
>  }
>  
> +/*
> + * VM Create with customized parameters
> + *
> + * Input Args:
> + *   mode - VM Mode (e.g. VM_MODE_P52V48_4K)
> + *   nr_vcpus - VCPU count
> + *   slot0_mem_pages - Slot0 physical memory size
> + *   extra_mem_pages - Non-slot0 physical memory total size
> + *   num_percpu_pages - Per-cpu physical memory pages
> + *   guest_code - Guest entry point
> + *   vcpuids - VCPU IDs
> + *
> + * Output Args: None
> + *
> + * Return:
> + *   Pointer to opaque structure that describes the created VM.
> + *
> + * Creates a VM with the mode specified by mode (e.g. VM_MODE_P52V48_4K),
> + * with customized slot0 memory size, at least 512 pages currently.
> + * extra_mem_pages is only used to calculate the maximum page table size,
> + * no real memory allocation for non-slot0 memory in this function.
> + */
>  struct kvm_vm *vm_create_with_vcpus(enum vm_guest_mode mode, uint32_t nr_vcpus,
> -				    uint64_t extra_mem_pages, uint32_t num_percpu_pages,
> -				    void *guest_code, uint32_t vcpuids[])
> +				    uint64_t slot0_mem_pages, uint64_t extra_mem_pages,
> +				    uint32_t num_percpu_pages, void *guest_code,
> +				    uint32_t vcpuids[])
>  {
> +	uint64_t vcpu_pages, extra_pg_pages, pages;
> +	struct kvm_vm *vm;
> +	int i;
> +
> +	/* Force slot0 memory size not small than DEFAULT_GUEST_PHY_PAGES */
> +	if (slot0_mem_pages < DEFAULT_GUEST_PHY_PAGES)
> +		slot0_mem_pages = DEFAULT_GUEST_PHY_PAGES;
> +
>  	/* The maximum page table size for a memory region will be when the
>  	 * smallest pages are used. Considering each page contains x page
>  	 * table descriptors, the total extra size for page tables (for extra
>  	 * N pages) will be: N/x+N/x^2+N/x^3+... which is definitely smaller
>  	 * than N/x*2.
>  	 */
> -	uint64_t vcpu_pages = (DEFAULT_STACK_PGS + num_percpu_pages) * nr_vcpus;
> -	uint64_t extra_pg_pages = (extra_mem_pages + vcpu_pages) / PTES_PER_MIN_PAGE * 2;
> -	uint64_t pages = DEFAULT_GUEST_PHY_PAGES + vcpu_pages + extra_pg_pages;
> -	struct kvm_vm *vm;
> -	int i;
> +	vcpu_pages = (DEFAULT_STACK_PGS + num_percpu_pages) * nr_vcpus;
> +	extra_pg_pages = (slot0_mem_pages + extra_mem_pages + vcpu_pages) / PTES_PER_MIN_PAGE * 2;

We weren't including the slot0 memory (which was DEFAULT_GUEST_PHY_PAGES)
in the extra_pg_pages calculation before, since they weren't considered
"extra". It's probably a good idea to do this calculation for the caller,
but it's making a change not called out in the commit message.

> +	pages = slot0_mem_pages + vcpu_pages + extra_pg_pages;
>  
>  	TEST_ASSERT(nr_vcpus <= kvm_check_cap(KVM_CAP_MAX_VCPUS),
>  		    "nr_vcpus = %d too large for host, max-vcpus = %d",
> @@ -354,8 +383,8 @@ struct kvm_vm *vm_create_default_with_vcpus(uint32_t nr_vcpus, uint64_t extra_me
>  					    uint32_t num_percpu_pages, void *guest_code,
>  					    uint32_t vcpuids[])
>  {
> -	return vm_create_with_vcpus(VM_MODE_DEFAULT, nr_vcpus, extra_mem_pages,
> -				    num_percpu_pages, guest_code, vcpuids);
> +	return vm_create_with_vcpus(VM_MODE_DEFAULT, nr_vcpus, DEFAULT_GUEST_PHY_PAGES,
> +				    extra_mem_pages, num_percpu_pages, guest_code, vcpuids);
>  }
>  
>  struct kvm_vm *vm_create_default(uint32_t vcpuid, uint64_t extra_mem_pages,
> diff --git a/tools/testing/selftests/kvm/lib/perf_test_util.c b/tools/testing/selftests/kvm/lib/perf_test_util.c
> index abf381800a59..7397ca299835 100644
> --- a/tools/testing/selftests/kvm/lib/perf_test_util.c
> +++ b/tools/testing/selftests/kvm/lib/perf_test_util.c
> @@ -69,7 +69,7 @@ struct kvm_vm *perf_test_create_vm(enum vm_guest_mode mode, int vcpus,
>  	TEST_ASSERT(vcpu_memory_bytes % perf_test_args.guest_page_size == 0,
>  		    "Guest memory size is not guest page size aligned.");
>  
> -	vm = vm_create_with_vcpus(mode, vcpus,
> +	vm = vm_create_with_vcpus(mode, vcpus, DEFAULT_GUEST_PHY_PAGES,
>  				  (vcpus * vcpu_memory_bytes) / perf_test_args.guest_page_size,
>  				  0, guest_code, NULL);
>  
> -- 
> 2.25.1
>

Besides the extra_pg_pages comment

Reviewed-by: Andrew Jones <drjones@redhat.com>

Thanks,
drew