Re: [PATCH V6 4/7] KVM: selftests: add support for protected vm_vaddr_* allocations

[Sean Christopherson <seanjc@google.com>]

On Tue, Jan 10, 2023, Peter Gonda wrote:
> From: Michael Roth <michael.roth@amd.com>
> 
> Test programs may wish to allocate shared vaddrs for things like
> sharing memory with the guest. Since protected vms will have their
> memory encrypted by default an interface is needed to explicitly
> request shared pages.
> 
> Implement this by splitting the common code out from vm_vaddr_alloc()
> and introducing a new vm_vaddr_alloc_shared().
> 
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Sean Christopherson <seanjc@google.com>
> Cc: Vishal Annapurve <vannapurve@google.com>
> Cc: Ackerley Tng <ackerleytng@google.com>
> cc: Andrew Jones <andrew.jones@linux.dev>
> Signed-off-by: Michael Roth <michael.roth@amd.com>
> Signed-off-by: Peter Gonda <pgonda@google.com>
> ---
>  .../selftests/kvm/include/kvm_util_base.h     |  1 +
>  tools/testing/selftests/kvm/lib/kvm_util.c    | 21 +++++++++++++++----
>  2 files changed, 18 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/testing/selftests/kvm/include/kvm_util_base.h b/tools/testing/selftests/kvm/include/kvm_util_base.h
> index f84d7777d5ca..5f3150ecfbbf 100644
> --- a/tools/testing/selftests/kvm/include/kvm_util_base.h
> +++ b/tools/testing/selftests/kvm/include/kvm_util_base.h
> @@ -435,6 +435,7 @@ vm_vaddr_t vm_vaddr_unused_gap(struct kvm_vm *vm, size_t sz, vm_vaddr_t vaddr_mi
>  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);

Wrap.

>  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 ba771c2d949d..0d0a7ad7632d 100644
> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> @@ -1305,15 +1305,17 @@ vm_vaddr_t vm_vaddr_unused_gap(struct kvm_vm *vm, size_t sz,
>  	return pgidx_start * vm->page_size;
>  }
>  
> -vm_vaddr_t __vm_vaddr_alloc(struct kvm_vm *vm, size_t sz, vm_vaddr_t vaddr_min,
> -			    enum kvm_mem_region_type type)
> +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)

s/encrypt/protected, or maybe mark_protected so that it's clear that it's a command.

>  {
>  	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,
> +	vm_paddr_t paddr = _vm_phy_pages_alloc(vm, pages,
>  					      KVM_UTIL_MIN_PFN * vm->page_size,
> -					      vm->memslots[type]);
> +					      vm->memslots[type], encrypt);
>  
>  	/*
>  	 * Find an unused range of virtual page addresses of at least
> @@ -1333,6 +1335,17 @@ vm_vaddr_t __vm_vaddr_alloc(struct kvm_vm *vm, size_t sz, vm_vaddr_t vaddr_min,
>  	return vaddr_start;
>  }
>  
> +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);
> +}
> +
> +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);

This shouldn't be MEM_REGION_TEST_DATA, because then the ucall patches changes
from MEM_REGION_DATA to MEM_REGION_TEST_DATA, which I suspect will break ARM's
page_fault_test.  So, we probably need to have vm_vaddr_alloc_shared() be a true
mirror of the non-shared version and take @type.