Re: [RFC PATCH v5 01/29] KVM: selftests: Add function to allow one-to-one GVA to GPA mappings

[Binbin Wu <binbin.wu@linux.intel.com>]

On 12/13/2023 4:46 AM, Sagi Shahar wrote:
> From: Ackerley Tng <ackerleytng@google.com>
>
> One-to-one GVA to GPA mappings can be used in the guest to set up boot
> sequences during which paging is enabled, hence requiring a transition
> from using physical to virtual addresses in consecutive instructions.
>
> Signed-off-by: Ackerley Tng <ackerleytng@google.com>
> Signed-off-by: Ryan Afranji <afranji@google.com>
> Signed-off-by: Sagi Shahar <sagis@google.com>
> ---
>   .../selftests/kvm/include/kvm_util_base.h     |  2 +
>   tools/testing/selftests/kvm/lib/kvm_util.c    | 63 ++++++++++++++++---
>   2 files changed, 55 insertions(+), 10 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/include/kvm_util_base.h b/tools/testing/selftests/kvm/include/kvm_util_base.h
> index 1426e88ebdc7..c2e5c5f25dfc 100644
> --- a/tools/testing/selftests/kvm/include/kvm_util_base.h
> +++ b/tools/testing/selftests/kvm/include/kvm_util_base.h
> @@ -564,6 +564,8 @@ vm_vaddr_t vm_vaddr_alloc(struct kvm_vm *vm, size_t sz, vm_vaddr_t vaddr_min);
>   vm_vaddr_t __vm_vaddr_alloc(struct kvm_vm *vm, size_t sz, vm_vaddr_t vaddr_min,
>   			    enum kvm_mem_region_type type);
>   vm_vaddr_t vm_vaddr_alloc_shared(struct kvm_vm *vm, size_t sz, vm_vaddr_t vaddr_min);
> +vm_vaddr_t vm_vaddr_alloc_1to1(struct kvm_vm *vm, size_t sz,
> +			       vm_vaddr_t vaddr_min, uint32_t data_memslot);
>   vm_vaddr_t vm_vaddr_alloc_pages(struct kvm_vm *vm, int nr_pages);
>   vm_vaddr_t __vm_vaddr_alloc_page(struct kvm_vm *vm,
>   				 enum kvm_mem_region_type type);
> diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
> index febc63d7a46b..4f1ae0f1eef0 100644
> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> @@ -1388,17 +1388,37 @@ vm_vaddr_t vm_vaddr_unused_gap(struct kvm_vm *vm, size_t sz,
>   	return pgidx_start * vm->page_size;
>   }
>   
> +/*
> + * VM Virtual Address Allocate Shared/Encrypted
> + *
> + * Input Args:
> + *   vm - Virtual Machine
> + *   sz - Size in bytes
> + *   vaddr_min - Minimum starting virtual address
> + *   paddr_min - Minimum starting physical address
> + *   data_memslot - memslot number to allocate in
> + *   encrypt - Whether the region should be handled as encrypted
> + *
> + * Output Args: None
> + *
> + * Return:
> + *   Starting guest virtual address
> + *
> + * Allocates at least sz bytes within the virtual address space of the vm
> + * given by vm.  The allocated bytes are mapped to a virtual address >=
> + * the address given by vaddr_min.  Note that each allocation uses a
> + * a unique set of pages, with the minimum real allocation being at least
> + * a page.
> + */
>   static vm_vaddr_t ____vm_vaddr_alloc(struct kvm_vm *vm, size_t sz,
> -				     vm_vaddr_t vaddr_min,
> -				     enum kvm_mem_region_type type,
> -				     bool encrypt)
> +				     vm_vaddr_t vaddr_min, vm_paddr_t paddr_min,
> +				     uint32_t data_memslot, bool encrypt)
>   {
>   	uint64_t pages = (sz >> vm->page_shift) + ((sz % vm->page_size) != 0);
>   
>   	virt_pgd_alloc(vm);
> -	vm_paddr_t paddr = _vm_phy_pages_alloc(vm, pages,
> -					      KVM_UTIL_MIN_PFN * vm->page_size,
> -					      vm->memslots[type], encrypt);
> +	vm_paddr_t paddr = _vm_phy_pages_alloc(vm, pages, paddr_min,
> +					       data_memslot, encrypt);
>   
>   	/*
>   	 * Find an unused range of virtual page addresses of at least
> @@ -1408,8 +1428,7 @@ static vm_vaddr_t ____vm_vaddr_alloc(struct kvm_vm *vm, size_t sz,
>   
>   	/* Map the virtual pages. */
>   	for (vm_vaddr_t vaddr = vaddr_start; pages > 0;
> -		pages--, vaddr += vm->page_size, paddr += vm->page_size) {
> -
> +	     pages--, vaddr += vm->page_size, paddr += vm->page_size) {
>   		virt_pg_map(vm, vaddr, paddr);
>   
>   		sparsebit_set(vm->vpages_mapped, vaddr >> vm->page_shift);
> @@ -1421,12 +1440,16 @@ static vm_vaddr_t ____vm_vaddr_alloc(struct kvm_vm *vm, size_t sz,
>   vm_vaddr_t __vm_vaddr_alloc(struct kvm_vm *vm, size_t sz, vm_vaddr_t vaddr_min,
>   			    enum kvm_mem_region_type type)
>   {
> -	return ____vm_vaddr_alloc(vm, sz, vaddr_min, type, vm->protected);
> +	return ____vm_vaddr_alloc(vm, sz, vaddr_min,
> +				  KVM_UTIL_MIN_PFN * vm->page_size,
> +				  vm->memslots[type], vm->protected);
>   }
>   
>   vm_vaddr_t vm_vaddr_alloc_shared(struct kvm_vm *vm, size_t sz, vm_vaddr_t vaddr_min)
>   {
> -	return ____vm_vaddr_alloc(vm, sz, vaddr_min, MEM_REGION_TEST_DATA, false);
> +	return ____vm_vaddr_alloc(vm, sz, vaddr_min,
> +				  KVM_UTIL_MIN_PFN * vm->page_size,
> +				  vm->memslots[MEM_REGION_TEST_DATA], false);
>   }
>   
>   /*
> @@ -1453,6 +1476,26 @@ vm_vaddr_t vm_vaddr_alloc(struct kvm_vm *vm, size_t sz, vm_vaddr_t vaddr_min)
>   	return __vm_vaddr_alloc(vm, sz, vaddr_min, MEM_REGION_TEST_DATA);
>   }
>   
> +/**
> + * Allocate memory in @vm of size @sz in memslot with id @data_memslot,
> + * beginning with the desired address of @vaddr_min.
> + *
> + * If there isn't enough memory at @vaddr_min, find the next possible address
> + * that can meet the requested size in the given memslot.
> + *
> + * Return the address where the memory is allocated.
> + */
> +vm_vaddr_t vm_vaddr_alloc_1to1(struct kvm_vm *vm, size_t sz,
> +			       vm_vaddr_t vaddr_min, uint32_t data_memslot)
> +{
> +	vm_vaddr_t gva = ____vm_vaddr_alloc(vm, sz, vaddr_min,
> +					    (vm_paddr_t)vaddr_min, data_memslot,
> +					    vm->protected);
> +	TEST_ASSERT_EQ(gva, addr_gva2gpa(vm, gva));

How can this be guaranteed?
For ____vm_vaddr_alloc(), generically there is no enforcement about the
identity of virtual and physical address.

> +
> +	return gva;
> +}
> +
>   /*
>    * VM Virtual Address Allocate Pages
>    *