Re: [PATCH 13/20] KVM: selftests: Add TEST_EXTRA memory region type for "special" memslots

[Itaru Kitayama]

On Wed, Aug 26, 2026 at 04:05:04PM -0700, Sean Christopherson wrote:
> And another memory region type to deal with extra, one-off memory regions,
> and use the new type to manage x86's SMRAM memslot, as another step towards
> taking the region type instead of the raw memslot in the physical page
> allocator APIs.
> 
> Alternatively, SMRAM setup could simply use the quad-underscore API to
> continue passing in the memslot, but a surprising number of tests use an
> "extra" memslot for a variety of reasons.  I.e. allocating memory from one
> (and exactly one) extra memslot isn't all that rare, and so should be
> treated as normal behavior, not as something extraordinary, as
> quad-underscore functions typically suggest.
> 
> Opportunistically add comments to document the intended usage of the types,
> as the difference between DATA, TEST_DATA, and TEST_EXTRA in particular
> isn't exactly obvious.
> 
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> ---
>  .../testing/selftests/kvm/include/kvm_util.h  | 37 ++++++++++++++++---
>  tools/testing/selftests/kvm/include/x86/smm.h |  2 +-
>  .../testing/selftests/kvm/lib/x86/processor.c |  7 ++--
>  3 files changed, 37 insertions(+), 9 deletions(-)
> 
> diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
> index 14f87c8a00ec..f4f4f360a10b 100644
> --- a/tools/testing/selftests/kvm/include/kvm_util.h
> +++ b/tools/testing/selftests/kvm/include/kvm_util.h
> @@ -82,11 +82,43 @@ struct userspace_mem_regions {
>  	DECLARE_HASHTABLE(slot_hash, 9);
>  };
>  
> +/*
> + * Memory region types are passed to various page allocators to communicate
> + * various properties and metadata related to the allocation.  Note, the
> + * descriptions below described the primary usage of each type.  Individual
> + * tests may allocate memory for other purposes.
> + *
> + * By default, all regions are mapped to memslot '0'.  Tests can override the
> + * memslot for any or all types, e.g. so that all test data is allocated from a
> + * curated memslot.
> + */

This is helpful as it wasn't so obvious to me. Thanks for adding the comments 
on the default behaviour.

Thanks,
Itaru.

>  enum kvm_mem_region_type {
> +	/*
> +	 * The CODE region is used by lib/elf when loading the test's code into
> +	 * guest memory.
> +	 */
>  	MEM_REGION_CODE,
> +	/*
> +	 * The DATA region is used to allocate core data structures, e.g. vCPU
> +	 * stacks, VM exception tables, x86's TSS, etc.
> +	 */
>  	MEM_REGION_DATA,
> +	/*
> +	 * The PT region, a.k.a. Page Table region, is used to allocate page
> +	 * table pages.
> +	 */
>  	MEM_REGION_PT,
> +	/*
> +	 * The TEST_DATA region is used for allocating test data that is either
> +	 * test specific, and/or isn't considered a "core" data structure.
> +	 */
>  	MEM_REGION_TEST_DATA,
> +	/*
> +	 * The TEST_EXTRA region is for special snowflakes, where a test wants
> +	 * to create and use a one-off memslot, without impacting "normal" test
> +	 * data allocations.
> +	 */
> +	MEM_REGION_TEST_EXTRA,
>  	NR_MEM_REGIONS,
>  };
>  
> @@ -129,11 +161,6 @@ struct kvm_vm {
>  
>  	struct kvm_binary_stats stats;
>  
> -	/*
> -	 * KVM region slots. These are the default memslots used by page
> -	 * allocators, e.g., lib/elf uses the memslots[MEM_REGION_CODE]
> -	 * memslot.
> -	 */
>  	u32 memslots[NR_MEM_REGIONS];
>  };
>  
> diff --git a/tools/testing/selftests/kvm/include/x86/smm.h b/tools/testing/selftests/kvm/include/x86/smm.h
> index 2d1afa09819b..15faaa060126 100644
> --- a/tools/testing/selftests/kvm/include/x86/smm.h
> +++ b/tools/testing/selftests/kvm/include/x86/smm.h
> @@ -8,7 +8,7 @@
>  #define SMRAM_MEMSLOT	((1 << 16) | 1)
>  #define SMRAM_PAGES	(SMRAM_SIZE / PAGE_SIZE)
>  
> -void setup_smram(struct kvm_vm *vm, struct kvm_vcpu *vcpu, u64 smram_gpa,
> +void setup_smram(struct kvm_vm *vm, struct kvm_vcpu *vcpu, gpa_t smram_gpa,
>  		 const void *smi_handler, size_t handler_size);
>  
>  void inject_smi(struct kvm_vcpu *vcpu);
> diff --git a/tools/testing/selftests/kvm/lib/x86/processor.c b/tools/testing/selftests/kvm/lib/x86/processor.c
> index ea5fa59888af..b988eea373ad 100644
> --- a/tools/testing/selftests/kvm/lib/x86/processor.c
> +++ b/tools/testing/selftests/kvm/lib/x86/processor.c
> @@ -1468,11 +1468,12 @@ bool kvm_arch_has_default_irqchip(void)
>  	return true;
>  }
>  
> -void setup_smram(struct kvm_vm *vm, struct kvm_vcpu *vcpu, u64 smram_gpa,
> +void setup_smram(struct kvm_vm *vm, struct kvm_vcpu *vcpu, gpa_t smram_gpa,
>  		 const void *smi_handler, size_t handler_size)
>  {
> -	vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS, smram_gpa,
> -				    SMRAM_MEMSLOT, SMRAM_PAGES, 0);
> +	vm_override_mem_region(vm, MEM_REGION_TEST_EXTRA, VM_MEM_SRC_ANONYMOUS,
> +			       smram_gpa, SMRAM_MEMSLOT, SMRAM_PAGES);
> +
>  	TEST_ASSERT(vm_phy_pages_alloc(vm, SMRAM_PAGES, smram_gpa,
>  				       SMRAM_MEMSLOT) == smram_gpa,
>  		    "Could not allocate guest physical addresses for SMRAM");
> -- 
> 2.55.0.887.g758fc8c411-goog
>