[6.6] [Feature] : AMD SEV-SNP feature backport for OpenAnolis 6.6 kernel - patch set 1 · Pull Request !6878 · anolis/cloud-kernel

bugzilla: https://bugzilla.openanolis.cn/show_bug.cgi?id=34453

**AMD SEV-SNP Backport for OpenAnolis 6.6 Kernel — Set-1**

**Patch List**

```
KVM: X86: Reduce size of kvm_vcpu_arch structure when CONFIG_KVM_XEN=n
hugetlbfs: convert to new timestamp accessors
KVM: selftests: Drop unused kvm_userspace_memory_region_find() helper
KVM: selftests: Convert lib's mem regions to KVM_SET_USER_MEMORY_REGION2
KVM: selftests: Add support for creating private memslots
KVM: selftests: Add helpers to convert guest memory b/w private and shared
KVM: selftests: Add helpers to do KVM_HC_MAP_GPA_RANGE hypercalls (x86)
KVM: selftests: Introduce VM "shape" to allow tests to specify the VM type
KVM: selftests: Add GUEST_SYNC[1-6] macros for synchronizing more data
KVM: selftests: Add x86-only selftest for private memory conversions
KVM: selftests: Add KVM_SET_USER_MEMORY_REGION2 helper
KVM: selftests: Expand set_memory_region_test to validate guest_memfd()
KVM: selftests: Add basic selftest for guest_memfd()
KVM: selftests: Test KVM exit behavior for private memory/access
KVM: selftests: Add a memory region subtest to validate invalid flags
fs: Rename mapping private members
selftests/kvm: fix compilation on non-x86_64 platforms
KVM: selftests: Drop the single-underscore ioctl() helpers
KVM: selftests: Add logic to detect if ioctl() failed because VM was killed
KVM: x86: Remove 'return void' expression for 'void function'
Support rv32 ULEB128 test
KVM: x86/xen: Remove unneeded xen context from kvm_arch when !CONFIG_KVM_XEN
KVM: VMX: Split off hyperv_evmcs.{ch}
KVM: nVMX: Split off helper for emulating VMCLEAR on Hyper-V eVMCS
KVM: nVMX: Move guest_cpuid_has_evmcs() to hyperv.h
```

---

The AMD SEV-SNP backport for the OpenAnolis 6.6 kernel is planned across multiple phases. This is Set 1, consisting of 25 preparatory patches that lay the foundational groundwork required before the core SEV-SNP enablement patches can be applied cleanly. The changes focus on building the KVM selftest infrastructure for private/confidential memory (guest_memfd), modernising the KVM memory region API, refactoring KVM's Hyper-V and Xen code paths for optional compilation, and resolving cross-cutting build and API cleanups. These patches align the Anolis 6.6 kernel with the upstream prerequisites of the SEV-SNP series while preserving KABI compatibility and Anolis-specific configuration constraints.

---

**Key Bug Fixes:**
 
- **Compilation failure on non-x86_64 platforms**: Fixed a build error in `test_invalid_memory_region_flags` caused by undefined `MEM_REGION_SLOT` and `MEM_REGION_GPA` macros on non-x86 architectures.
- **rv32 ULEB128 test failure**: Corrected the ULEB128 module linking test to use opcodes compatible with both rv32 and rv64, fixing a build failure on 32-bit RISC-V targets.
- **`return void` pedantic warning in KVM x86**: Removed a redundant `return void` expression from `kvm_vcpu_ioctl_x86_get_xsave()`, silencing a `[-Wpedantic]` compiler warning.
- **Backport deviation in KVM_SET_USER_MEMORY_REGION2**: Corrected a deviation from an earlier Anolis backport where `vm_ioctl()` was left calling `KVM_SET_USER_MEMORY_REGION` instead of `KVM_SET_USER_MEMORY_REGION2`, realigning with upstream intent.
- **Obscure VM-killed error message**: Replaced a cryptic `Input/output error` on ioctl teardown with a clear `KVM killed/bugged the VM, check the kernel log for clues` message to simplify test failure triage.
---
 
**Feature Additions:**
 
- **guest_memfd private memslot support in selftests**: Added support for creating `KVM_MEM_PRIVATE` memslots via `KVM_CREATE_GUEST_MEMFD` and `KVM_SET_USER_MEMORY_REGION2`. The new `vm_mem_add()` is the unified entry point; `vm_userspace_mem_region_add()` is kept as a backward-compatible wrapper.
- **Private/shared memory conversion helpers**: Added helpers to convert guest memory between private and shared via KVM memory attributes, plus `fallocate()`-based helpers to free and re-allocate guest_memfd pages.
- **KVM_HC_MAP_GPA_RANGE hypercall helpers (x86)**: Added x86 guest-side helpers to invoke the `KVM_HC_MAP_GPA_RANGE` hypercall, enabling selftests to coordinate private↔shared conversions between host and guest.
- **VM "shape" abstraction**: Introduced `struct vm_shape` to bundle `vm_guest_mode` with a KVM-defined `type` field, allowing tests to request specific VM types (e.g., `KVM_X86_SW_PROTECTED_VM`) needed for SEV-SNP and TDX.
- **GUEST_SYNC[1-6] macros**: Extended the guest↔host sync macro set to pass up to six data values per sync point via `ucall()`, avoiding the need for shared memory in simple multi-value synchronisation.
- **VM-killed ioctl detection**: Added logic to detect when an ioctl failure is caused by KVM internally killing the VM (`-EIO`), producing a targeted error message and distinguishing it from legitimate ioctl errors.
---
 
**Logic & Performance Improvements:**
 
- **KVM selftest memory region API modernisation**: Converted all internal selftest library memory region management to `KVM_SET_USER_MEMORY_REGION2`, enabling private memslot support to be added incrementally per test.
- **kvm_vcpu_arch structure size reduction**: Moved Xen-specific fields under `#ifdef CONFIG_KVM_XEN`, shrinking `kvm_vcpu_arch` from ~5100 to ~4400 bytes per vCPU when `CONFIG_KVM_XEN=n`.
- **Xen context removal when CONFIG_KVM_XEN=n**: Removed the Xen emulation context from `kvm_arch` when disabled, making any incorrect access immediately visible at compile time.
- **Hyper-V eVMCS code reorganisation**: Split eVMCS code into dedicated `hyperv_evmcs.{c,h}` files and extracted `nested_evmcs_handle_vmclear()` as a standalone helper, preparing for optional Hyper-V emulation via Kconfig.
- **address_space member rename (fs layer)**: Renamed `mapping->private_*` members to `mapping->i_private_*` for naming consistency. All references in `virt/kvm/guest_memfd.c` and `fs/inode.c` are updated accordingly.
---
 
**Selftest Coverage Added:**
 
- **Private memory conversion test (x86-only)**: Added an x86 selftest exercising private↔shared memory conversions with configurable memslot counts, verifying correct SPTE zapping, punch-hole zero reads, and multi-memslot attribute setting.
- **guest_memfd basic selftest**: Added a standalone test validating core guest_memfd lifecycle: creation, memslot binding, and basic access pattern verification.
- **set_memory_region_test expansion**: Extended the existing memory region test to cover positive and negative testcases for private memory and invalid flag combinations with `KVM_SET_USER_MEMORY_REGION2`.
- **KVM exit behaviour for private memory**: Added a test verifying that KVM correctly exits to userspace with `KVM_EXIT_MEMORY_FAULT` when a private memslot is deleted or has no valid private backing during guest access.
---
 
**Robustness & Safety:**
 
- **Backport compatibility**: All changes preserve Anolis KABI-compatible interfaces; deviations from earlier Anolis backports are explicitly identified and corrected.
- **Opt-in private memslot design**: Private memslot support is fully opt-in — existing tests using `vm_userspace_mem_region_add()` continue to work unchanged.
- **Safe fd lifecycle management**: guest_memfd fds passed into `vm_mem_add()` are `dup()`'d internally, allowing safe independent closure by both the caller and the test framework without use-after-free risk.

---

**Testing**

```
The test setup and test cases are documented in the Bugzilla issue. Validation should be performed only after all SEV-SNP patches have been merged into the Anolis kernel. 
```

类型	指派人员	状态
审查	hsiangkao josephhz xunlei JeffleXu 半叶枫尘 zhongjiang Artie Ding winterddd xueshuai guobin vxuyu dtc maqiao-alibaba baolin.wang Tony Lu 冯光辉 Guixin Liu kun-llfl Xuchun Shang XiangZao fangyu0809	已完成 (0/0人)
测试	小龙已测试通过	已完成 (1/1人)

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