From: Lisa Wang <wyihan@google.com>
To: sashiko-reviews@lists.linux.dev
Cc: kvm@vger.kernel.org
Subject: Re: [PATCH v15 07/23] KVM: selftests: Add TDX boot code
Date: Mon, 5 Oct 2026 22:31:06 +0000 [thread overview]
Message-ID: <asQlKs3pxOjhLUp1@google.com> (raw)
In-Reply-To: <20261002091330.4B5D31F00899@smtp.kernel.org>
On Fri, Oct 02, 2026 at 09:13:29AM +0000, sashiko-bot@kernel.org wrote:
> [ ... ]
>
> > + /*
> > + * Find the address of struct td_per_vcpu_parameters for this
> > + * vCPU based on esi (TDX spec: initialized with vCPU id). Put
> > + * struct address into eax for indirect addressing.
> > + */
> > + movl $SIZEOF_TD_PER_VCPU_PARAMETERS, %eax
> > + mul %esi
>
> [Severity: Medium]
> Is it correct to read the vCPU index from %esi in td_boot here?
>
> According to the TDX architecture specification (via TDH.VP.INIT), the vCPU
> index is initialized in the %ecx register, while %esi is initialized to 0.
>
> If %esi is used, will all vCPUs evaluate to index 0, causing them to
> incorrectly share the same stack and guest code pointer? This seems like it
> could corrupt the SMP stack and fail multi-vCPU tests.
According to the TDX spec, %esi is the vCPU index.
> [ ... ]
>
> > + /*
> > + * Set up control registers (x86 does not support moving memory
> > + * directly to a control register).
> > + */
> > + movl TD_BOOT_PARAMETERS_CR4(%ebx), %edi
> > + movl %edi, %cr4
> > + movl TD_BOOT_PARAMETERS_CR3(%ebx), %edi
> > + movl %edi, %cr3
> > + movl TD_BOOT_PARAMETERS_CR0(%ebx), %edi
> > + movl %edi, %cr0
> > +
> > + /* Switching to 64bit mode after ljmp and then jump to guest code */
> > + ljmp $(KERNEL_CS),$1f
>
> [Severity: Medium]
> Does td_boot miss a wrmsr to set EFER.LME before enabling paging?
>
> The TDX VM guest boot code enables paging (CR0.PG) and physical address
> extensions (CR4.PAE) here, but appears to omit writing the EFER MSR to set
> the Long Mode Enable (LME) bit.
>
> According to the x86 architecture, enabling paging without setting EFER.LME
> puts the processor into 32-bit PAE paging mode instead of 64-bit IA-32e
> mode.
>
> Will the subsequent far jump attempt to load a 64-bit code segment
> (KERNEL_CS has L=1), causing a #GP fault since it is invalid in 32-bit mode?
> It seems this might crash the guest VM unconditionally on every boot.
In TDX, TDH.VP.INIT initializes EFER.LME = 1 already.
> --
> Sashiko AI review · https://sashiko.dev/#/patchset/20261001-tdx-selftests-v15-0-7c62a5d8a992@google.com?part=7
next prev parent reply other threads:[~2026-10-05 22:31 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-01 19:37 [PATCH v15 00/23] TDX KVM selftests Lisa Wang
2026-10-01 19:37 ` [PATCH v15 01/23] KVM: selftests: Add macros to simplify creating VM shapes for non-default types Lisa Wang
2026-10-01 19:37 ` [PATCH v15 02/23] KVM: selftests: Update kvm_init_vm_address_properties() for TDX Lisa Wang
2026-10-01 19:37 ` [PATCH v15 03/23] KVM: selftests: Initialize the TDX VM Lisa Wang
2026-10-02 9:13 ` sashiko-bot
2026-10-05 21:26 ` Lisa Wang
2026-10-01 19:37 ` [PATCH v15 04/23] KVM: selftests: Expose segment definitions to assembly files Lisa Wang
2026-10-01 19:37 ` [PATCH v15 05/23] tools: include: Add kbuild.h for assembly structure offsets Lisa Wang
2026-10-01 19:37 ` [PATCH v15 06/23] KVM: selftests: Introduce structures for TDX guest boot parameters Lisa Wang
2026-10-01 19:37 ` [PATCH v15 07/23] KVM: selftests: Add TDX boot code Lisa Wang
2026-10-02 9:13 ` sashiko-bot
2026-10-05 22:31 ` Lisa Wang [this message]
2026-10-01 19:37 ` [PATCH v15 08/23] KVM: selftests: Expose functions to get default sregs values Lisa Wang
2026-10-01 19:37 ` [PATCH v15 09/23] KVM: selftests: Set up TDX boot code region Lisa Wang
2026-10-01 19:37 ` [PATCH v15 10/23] KVM: selftests: Set up TDX boot parameters region Lisa Wang
2026-10-02 9:13 ` sashiko-bot
2026-10-05 22:33 ` Lisa Wang
2026-10-01 19:37 ` [PATCH v15 11/23] KVM: selftests: Set shared attributes for ucall guest_memfd pages Lisa Wang
2026-10-01 19:37 ` [PATCH v15 12/23] KVM: selftests: Require guest_memfd for TDX VMs Lisa Wang
2026-10-01 19:37 ` [PATCH v15 13/23] KVM: selftests: Support guest_memfd in-place conversion Lisa Wang
2026-10-01 19:37 ` [PATCH v15 14/23] KVM: selftests: Expose function to allocate vCPU stack Lisa Wang
2026-10-02 9:13 ` sashiko-bot
2026-10-01 19:37 ` [PATCH v15 15/23] KVM: selftests: Call KVM_TDX_INIT_VCPU when creating a new TDX vcpu Lisa Wang
2026-10-01 19:37 ` [PATCH v15 16/23] KVM: selftests: Load per-vCPU guest stack in TDX boot parameters Lisa Wang
2026-10-02 9:13 ` sashiko-bot
2026-10-07 19:07 ` Lisa Wang
2026-10-01 19:37 ` [PATCH v15 17/23] KVM: selftests: Set entry point for TDX guest code Lisa Wang
2026-10-02 9:13 ` sashiko-bot
2026-10-01 19:37 ` [PATCH v15 18/23] KVM: selftests: Add helpers to init TDX memory and finalize VM Lisa Wang
2026-10-01 19:37 ` [PATCH v15 19/23] KVM: selftests: Finalize TDX VM in kvm_arch_vm_finalize_vcpus() Lisa Wang
2026-10-01 19:37 ` [PATCH v15 20/23] KVM: selftests: Add a helper to issue TDVMCALLs from the TDX vm Lisa Wang
2026-10-02 9:13 ` sashiko-bot
2026-10-01 19:37 ` [PATCH v15 21/23] KVM: selftests: Add support for per-VM ucall ops on x86 Lisa Wang
2026-10-02 9:13 ` sashiko-bot
2026-10-01 19:37 ` [PATCH v15 22/23] KVM: selftests: Add support for TDX ucalls, via TDVMCALL_REPORT_FATAL_ERROR Lisa Wang
2026-10-02 9:13 ` sashiko-bot
2026-10-01 19:37 ` [PATCH v15 23/23] KVM: selftests: Add TDX lifecycle test Lisa Wang
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