Message-ID: <n5cjwr3klovu7tqcchptvmr6yieyhvnv5muv7zyvcbo5itskew@6rzo4ohctdhv>
Date: Tue, 18 Nov 2025 22:25:40 +0000
From: Yosry Ahmed <yosry.ahmed@...ux.dev>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>, Jim Mattson <jmattson@...gle.com>, 
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 00/23] Extend test coverage for nested SVM

On Tue, Oct 21, 2025 at 07:47:13AM +0000, Yosry Ahmed wrote:
> There are multiple selftests exercising nested VMX that are not specific
> to VMX (at least not anymore). Extend their coverage to nested SVM.
> 
> This version is significantly different (and longer) than v1 [1], mainly
> due to the change of direction to reuse __virt_pg_map() for nested EPT/NPT
> mappings instead of extending the existing nested EPT infrastructure. It
> also has a lot more fixups and cleanups.
> 
> This series depends on two other series:
> - "KVM: SVM: GIF and EFER.SVME are independent" [2]
> - "KVM: selftests: Add test of SET_NESTED_STATE with 48-bit L2 on 57-bit L1" [3]

v2 of Jim's series switches all tests to use 57-bit by default when
available:
https://lore.kernel.org/kvm/20251028225827.2269128-4-jmattson@google.com/

This breaks moving nested EPT mappings to use __virt_pg_map() because
nested EPTs are hardcoded to use 4-level paging, while __virt_pg_map()
will assume we're using 5-level paging.

Patch #16 ("KVM: selftests: Use __virt_pg_map() for nested EPTs") will
need the following diff to make nested EPTs use the same paging level as
the guest:

diff --git a/tools/testing/selftests/kvm/lib/x86_64/vmx.c b/tools/testing/selftests/kvm/lib/x86_64/vmx.c
index 358143bf8dd0d..8bacb74c00053 100644
--- a/tools/testing/selftests/kvm/lib/x86/vmx.c
+++ b/tools/testing/selftests/kvm/lib/x86/vmx.c
@@ -203,7 +203,7 @@ static inline void init_vmcs_control_fields(struct vmx_pages *vmx)
                uint64_t ept_paddr;
                struct eptPageTablePointer eptp = {
                        .memory_type = X86_MEMTYPE_WB,
-                       .page_walk_length = 3, /* + 1 */
+                       .page_walk_length = get_cr4() & X86_CR4_LA57 ? 4 : 3, /* + 1 */
                        .ad_enabled = ept_vpid_cap_supported(VMX_EPT_VPID_CAP_AD_BITS),
                        .address = vmx->eptp_gpa >> PAGE_SHIFT_4K,
                };


Which will conflict at patch #17, and should end up looking like this:

	uint64_t eptp = vmx->eptp_gpa | EPTP_WB;

	eptp |= get_cr4() & X86_CR4_LA57 ? EPTP_PWL_5 : EPTP_PWL_4;

Sean, let me know if you prefer that I rebase this series on top of
Jim's v2 and resend, or if you'll fix it up while applying.

> 
> The dependency on the former is because set_nested_state_test is now
> also a regression test for that fix. The dependency on the latter is
> purely to avoid conflicts.
> 
> The patch ordering is not perfect, I did some cleanups toward the end
> that arguably should have been moved to the beginning, but I had to stop
> rebasing and send the patches out at some point:
> 
> Block #1 (patch 1 to patch 7):
> - Direct successors to the first 6 patches in v1, addressing review
>   comments from Jim and collecting his review tags. These patch extend 5
>   of the nVMX tests to cover nSVM.
> 
> Block #2 (patch 8 to patch 11):
> - Miscellaneous fixups and cleanups.
> 
> Block #3 (patch 11 to patch 17):
> - Moving nested EPT mapping functions to use __virt_pg_map(), patches 11
>   to 15 do the prep work, and patch 16 does the switch. Patch 17 is a
>   minor cleanup on top (which arguably fits better in block #2).
> 
> Block #4 (patch 18 to 23):
> - Patches 18 to 22 are prep work to generalize the nested EPT mapping
>   code to work with nested NPT, and patch 23 finally extends the nested
>   dirty logging test to work with nSVM using the nested NPT
>   infrastructure. Patch 19 is admittedly an imposter in this block and
>   should have been in block #2.
> 
> [1]https://lore.kernel.org/kvm/20251001145816.1414855-1-yosry.ahmed@linux.dev/
> [2]https://lore.kernel.org/kvm/20251009223153.3344555-1-jmattson@google.com/
> [3]https://lore.kernel.org/kvm/20250917215031.2567566-1-jmattson@google.com/
> 
> Yosry Ahmed (23):
>   KVM: selftests: Minor improvements to asserts in
>     test_vmx_nested_state()
>   KVM: selftests: Extend vmx_set_nested_state_test to cover SVM
>   KVM: selftests: Extend vmx_close_while_nested_test to cover SVM
>   KVM: selftests: Extend vmx_nested_tsc_scaling_test to cover SVM
>   KVM: selftests: Move nested invalid CR3 check to its own test
>   KVM: selftests: Extend nested_invalid_cr3_test to cover SVM
>   KVM: selftests: Extend vmx_tsc_adjust_test to cover SVM
>   KVM: selftests: Stop hardcoding PAGE_SIZE in x86 selftests
>   KVM: selftests: Remove the unused argument to prepare_eptp()
>   KVM: selftests: Stop using __virt_pg_map() directly in tests
>   KVM: selftests: Make sure vm->vpages_mapped is always up-to-date
>   KVM: selftests: Parameterize the PTE bitmasks for virt mapping
>     functions
>   KVM: selftests: Pass the root GPA into virt_get_pte()
>   KVM: selftests: Pass the root GPA into __virt_pg_map()
>   KVM: selftests: Stop setting AD bits on nested EPTs on creation
>   KVM: selftests: Use __virt_pg_map() for nested EPTs
>   KVM: selftests: Kill eptPageTablePointer
>   KVM: selftests: Generalize nested mapping functions
>   KVM: selftests: Move nested MMU mapping functions outside of vmx.c
>   KVM: selftests: Stop passing a memslot to nested_map_memslot()
>   KVM: selftests: Allow kvm_cpu_has_ept() to be called on AMD CPUs
>   KVM: selftests: Set the user bit on nested MMU PTEs
>   KVM: selftests: Extend vmx_dirty_log_test to cover SVM
> 
>  tools/testing/selftests/kvm/Makefile.kvm      |  11 +-
>  .../testing/selftests/kvm/include/kvm_util.h  |   1 +
>  .../selftests/kvm/include/x86/processor.h     |  34 ++-
>  .../selftests/kvm/include/x86/svm_util.h      |   8 +
>  tools/testing/selftests/kvm/include/x86/vmx.h |  15 +-
>  tools/testing/selftests/kvm/lib/kvm_util.c    |   3 -
>  .../testing/selftests/kvm/lib/x86/memstress.c |   6 +-
>  .../testing/selftests/kvm/lib/x86/processor.c | 184 +++++++++++---
>  tools/testing/selftests/kvm/lib/x86/svm.c     |  19 ++
>  tools/testing/selftests/kvm/lib/x86/vmx.c     | 232 +++---------------
>  tools/testing/selftests/kvm/mmu_stress_test.c |   6 +-
>  ...ested_test.c => close_while_nested_test.c} |  42 +++-
>  .../selftests/kvm/x86/hyperv_features.c       |   2 +-
>  tools/testing/selftests/kvm/x86/hyperv_ipi.c  |  18 +-
>  .../selftests/kvm/x86/hyperv_tlb_flush.c      |   2 +-
>  ...rty_log_test.c => nested_dirty_log_test.c} | 102 +++++---
>  .../kvm/x86/nested_invalid_cr3_test.c         | 118 +++++++++
>  ...adjust_test.c => nested_tsc_adjust_test.c} |  79 +++---
>  ...aling_test.c => nested_tsc_scaling_test.c} |  48 +++-
>  ...d_state_test.c => set_nested_state_test.c} | 135 +++++++++-
>  .../selftests/kvm/x86/sev_smoke_test.c        |   2 +-
>  tools/testing/selftests/kvm/x86/state_test.c  |   2 +-
>  .../selftests/kvm/x86/userspace_io_test.c     |   2 +-
>  23 files changed, 695 insertions(+), 376 deletions(-)
>  rename tools/testing/selftests/kvm/x86/{vmx_close_while_nested_test.c => close_while_nested_test.c} (64%)
>  rename tools/testing/selftests/kvm/x86/{vmx_dirty_log_test.c => nested_dirty_log_test.c} (57%)
>  create mode 100644 tools/testing/selftests/kvm/x86/nested_invalid_cr3_test.c
>  rename tools/testing/selftests/kvm/x86/{vmx_tsc_adjust_test.c => nested_tsc_adjust_test.c} (61%)
>  rename tools/testing/selftests/kvm/x86/{vmx_nested_tsc_scaling_test.c => nested_tsc_scaling_test.c} (83%)
>  rename tools/testing/selftests/kvm/x86/{vmx_set_nested_state_test.c => set_nested_state_test.c} (67%)
> 
> -- 
> 2.51.0.869.ge66316f041-goog
> 

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