Re: [RFC V3 PATCH 5/6] selftests: kvm: x86: Execute VMs with private memory

On Fri, Oct 7, 2022 at 1:47 AM Sean Christopherson seanjc@google.com wrote:

On Fri, Aug 19, 2022, Vishal Annapurve wrote:

...

+/*

• • Execute KVM hypercall to change memory access type for a given gpa range.
• • Input Args:
• • type - memory conversion type TO_SHARED/TO_PRIVATE
• • gpa - starting gpa address
• • size - size of the range starting from gpa for which memory access needs

• • to be changed
    

• • Output Args: None
• • Return: None
• • Function called by guest logic in selftests to update the memory access type
• • for a given gpa range. This API is useful in exercising implicit conversion
• • path.
• */

+void guest_update_mem_access(enum mem_conversion_type type, uint64_t gpa,

• uint64_t size)
  

Provide wrappers to self-document what's going on, then the massive block comments go away. And the guts of this and guest_update_mem_map() are nearly identical.

Hmm, and we probably want to make it possible to do negative testing.

Then the one-off enums for TO_PRIVATE and whatnot go way too.

...

+{

• int ret = kvm_hypercall(KVM_HC_MAP_GPA_RANGE, gpa, size >> MIN_PAGE_SHIFT,
  

Needs an assert that @size is page aligned. And since these are x86-64 specific, just use PAGE_SHIFT. Huh, IS_ALIGNED() doesn't exist in selftests. That should be added, either by pulling in align.h or by adding the generic macros to kvm_util_base.h.

And then x86-64's processor.h can defined IS_PAGE_ALIGNED().

E.g.

static inline void __kvm_hypercall_map_gpa_range(uint64_t gpa, uint64_t size, uint64_t flags) { return = kvm_hypercall(KVM_HC_MAP_GPA_RANGE, gpa, size >> PAGE_SHIFT, flags, 0); }

static inline void kvm_hypercall_map_gpa_range(uint64_t gpa, uint64_t size, uint64_t flags) { int ret;

    GUEST_ASSERT_2(IS_PAGE_ALIGNED(gpa) && IS_PAGE_ALIGNED(size), gpa, size);

    ret = __kvm_hypercall_map_gpa_range(gpa, size, flags);
    GUEST_ASSERT_1(!ret, ret);

}

static inline kvm_hypercall_map_shared(uint64_t gpa, uint64_t size) { kvm_hypercall_map_gpa_range(gpa, size, KVM_CLR_GPA_RANGE_ENC_ACCESS); }

static inline kvm_hypercall_map_private(uint64_t gpa, uint64_t size) { kvm_hypercall_map_gpa_range(gpa, size, KVM_MARK_GPA_RANGE_ENC_ACCESS); }

...

+static void handle_vm_exit_map_gpa_hypercall(struct kvm_vm *vm,

•                         volatile struct kvm_run *run)
  

Pass in @vcpu, not a vm+run.

...

+{

• uint64_t gpa, npages, attrs, size;
  

• TEST_ASSERT(run->hypercall.nr == KVM_HC_MAP_GPA_RANGE,
  

•         "Unhandled Hypercall %lld\n", run->hypercall.nr);
  

• gpa = run->hypercall.args[0];
  

• npages = run->hypercall.args[1];
  

• size = npages << MIN_PAGE_SHIFT;
  

• attrs = run->hypercall.args[2];
  

• pr_info("Explicit conversion off 0x%lx size 0x%lx to %s\n", gpa, size,
  

•         (attrs & KVM_MAP_GPA_RANGE_ENCRYPTED) ? "private" : "shared");
  

• if (attrs & KVM_MAP_GPA_RANGE_ENCRYPTED)
  

•         vm_update_private_mem(vm, gpa, size, ALLOCATE_MEM);
  

• else
  

•         vm_update_private_mem(vm, gpa, size, UNBACK_MEM);
  

• run->hypercall.ret = 0;
  

+}

+static void handle_vm_exit_memory_error(struct kvm_vm *vm, volatile struct kvm_run *run)

Same here, take a @vcpu.

Ack. Will address these comments in the next series.