Re: [PATCH 1/9] KVM: selftests: Replace x86_page_size with raw levels

[Peter Xu <peterx@redhat.com>]

On Fri, Apr 29, 2022 at 06:39:27PM +0000, David Matlack wrote:
> x86_page_size is an enum used to communicate the desired page size with
> which to map a range of memory. Under the hood they just encode the
> desired level at which to map the page. This ends up being clunky in a
> few ways:
> 
>  - The name suggests it encodes the size of the page rather than the
>    level.
>  - In other places in x86_64/processor.c we just use a raw int to encode
>    the level.
> 
> Simplify this by just admitting that x86_page_size is just the level and
> using an int and some more obviously named macros (e.g. PG_LEVEL_1G).
> 
> Signed-off-by: David Matlack <dmatlack@google.com>
> ---
>  .../selftests/kvm/include/x86_64/processor.h  | 14 +++++-----
>  .../selftests/kvm/lib/x86_64/processor.c      | 27 +++++++++----------
>  .../selftests/kvm/max_guest_memory_test.c     |  2 +-
>  .../selftests/kvm/x86_64/mmu_role_test.c      |  2 +-
>  4 files changed, 22 insertions(+), 23 deletions(-)
> 
> diff --git a/tools/testing/selftests/kvm/include/x86_64/processor.h b/tools/testing/selftests/kvm/include/x86_64/processor.h
> index 37db341d4cc5..b512f9f508ae 100644
> --- a/tools/testing/selftests/kvm/include/x86_64/processor.h
> +++ b/tools/testing/selftests/kvm/include/x86_64/processor.h
> @@ -465,13 +465,13 @@ void vcpu_set_hv_cpuid(struct kvm_vm *vm, uint32_t vcpuid);
>  struct kvm_cpuid2 *vcpu_get_supported_hv_cpuid(struct kvm_vm *vm, uint32_t vcpuid);
>  void vm_xsave_req_perm(int bit);
>  
> -enum x86_page_size {
> -	X86_PAGE_SIZE_4K = 0,
> -	X86_PAGE_SIZE_2M,
> -	X86_PAGE_SIZE_1G,
> -};
> -void __virt_pg_map(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr,
> -		   enum x86_page_size page_size);
> +#define PG_LEVEL_4K 0
> +#define PG_LEVEL_2M 1
> +#define PG_LEVEL_1G 2

A nitpick is: we could have named those as PG_LEVEL_[PTE|PMD|PUD|PGD..]
rather than 4K|2M|..., then...

> +
> +#define PG_LEVEL_SIZE(_level) (1ull << (((_level) * 9) + 12))
> +
> +void __virt_pg_map(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr, int level);
>  
>  /*
>   * Basic CPU control in CR0
> diff --git a/tools/testing/selftests/kvm/lib/x86_64/processor.c b/tools/testing/selftests/kvm/lib/x86_64/processor.c
> index 9f000dfb5594..1a7de69e2495 100644
> --- a/tools/testing/selftests/kvm/lib/x86_64/processor.c
> +++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c
> @@ -199,15 +199,15 @@ static struct pageUpperEntry *virt_create_upper_pte(struct kvm_vm *vm,
>  						    uint64_t pt_pfn,
>  						    uint64_t vaddr,
>  						    uint64_t paddr,
> -						    int level,
> -						    enum x86_page_size page_size)
> +						    int current_level,
> +						    int target_level)
>  {
> -	struct pageUpperEntry *pte = virt_get_pte(vm, pt_pfn, vaddr, level);
> +	struct pageUpperEntry *pte = virt_get_pte(vm, pt_pfn, vaddr, current_level);
>  
>  	if (!pte->present) {
>  		pte->writable = true;
>  		pte->present = true;
> -		pte->page_size = (level == page_size);
> +		pte->page_size = (current_level == target_level);
>  		if (pte->page_size)
>  			pte->pfn = paddr >> vm->page_shift;
>  		else
> @@ -218,20 +218,19 @@ static struct pageUpperEntry *virt_create_upper_pte(struct kvm_vm *vm,
>  		 * a hugepage at this level, and that there isn't a hugepage at
>  		 * this level.
>  		 */
> -		TEST_ASSERT(level != page_size,
> +		TEST_ASSERT(current_level != target_level,
>  			    "Cannot create hugepage at level: %u, vaddr: 0x%lx\n",
> -			    page_size, vaddr);
> +			    current_level, vaddr);
>  		TEST_ASSERT(!pte->page_size,
>  			    "Cannot create page table at level: %u, vaddr: 0x%lx\n",
> -			    level, vaddr);
> +			    current_level, vaddr);
>  	}
>  	return pte;
>  }
>  
> -void __virt_pg_map(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr,
> -		   enum x86_page_size page_size)
> +void __virt_pg_map(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr, int level)
>  {
> -	const uint64_t pg_size = 1ull << ((page_size * 9) + 12);
> +	const uint64_t pg_size = PG_LEVEL_SIZE(level);
>  	struct pageUpperEntry *pml4e, *pdpe, *pde;
>  	struct pageTableEntry *pte;
>  
> @@ -256,15 +255,15 @@ void __virt_pg_map(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr,
>  	 * early if a hugepage was created.
>  	 */
>  	pml4e = virt_create_upper_pte(vm, vm->pgd >> vm->page_shift,
> -				      vaddr, paddr, 3, page_size);
> +				      vaddr, paddr, 3, level);
>  	if (pml4e->page_size)
>  		return;
>  
> -	pdpe = virt_create_upper_pte(vm, pml4e->pfn, vaddr, paddr, 2, page_size);
> +	pdpe = virt_create_upper_pte(vm, pml4e->pfn, vaddr, paddr, 2, level);
>  	if (pdpe->page_size)
>  		return;
>  
> -	pde = virt_create_upper_pte(vm, pdpe->pfn, vaddr, paddr, 1, page_size);
> +	pde = virt_create_upper_pte(vm, pdpe->pfn, vaddr, paddr, 1, level);

... here we could also potentially replace the 3/2/1s with the new macro
(or with existing naming number 3 will be missing a macro)?

>  	if (pde->page_size)
>  		return;

-- 
Peter Xu