Re: [PATCH v4 12/28] KVM: TDX: WARN if mirror SPTE doesn't have full RWX when creating S-EPT mapping
From: Huang, Kai <hidden>
Date: 2025-10-30 23:59:40
Also in:
kvm, kvm-riscv, kvmarm, linux-arm-kernel, linux-coco, linux-mips, linux-riscv, lkml, loongarch
On Thu, 2025-10-30 at 16:40 -0700, Sean Christopherson wrote:
On Thu, Oct 30, 2025, Kai Huang wrote:quoted
On Thu, 2025-10-30 at 13:09 -0700, Sean Christopherson wrote:quoted
Pass in the mirror_spte to kvm_x86_ops.set_external_spte() to provide symmetry with .remove_external_spte(), and assert in TDX that the mirror SPTE is shadow-present with full RWX permissions (the TDX-Module doesn't allow the hypervisor to control protections). Signed-off-by: Sean Christopherson <seanjc@google.com>Reviewed-by: Kai Huang <redacted> [...]quoted
static int tdx_sept_set_private_spte(struct kvm *kvm, gfn_t gfn, - enum pg_level level, kvm_pfn_t pfn) + enum pg_level level, u64 mirror_spte) { struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm); + kvm_pfn_t pfn = spte_to_pfn(mirror_spte); /* TODO: handle large pages. */ if (KVM_BUG_ON(level != PG_LEVEL_4K, kvm)) return -EIO; + WARN_ON_ONCE(!is_shadow_present_pte(mirror_spte) || + (mirror_spte & VMX_EPT_RWX_MASK) != VMX_EPT_RWX_MASK); +Nit: I am a little bit confused about when to use WARN_ON_ONCE() and KVM_BUG_ON(). :-)Very loosely: WARN if there's a decent chance carrying on might be fine, KVM_BUG_ON() if there's a good chance carrying on will crash the host and/or corrupt the guest, e.g. if KVM suspects a hardware/TDX-Module issue.
Makes sense. Thanks.