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Message-ID: <20250226195529.2314580-24-pbonzini@redhat.com>
Date: Wed, 26 Feb 2025 14:55:23 -0500
From: Paolo Bonzini <pbonzini@...hat.com>
To: linux-kernel@...r.kernel.org,
kvm@...r.kernel.org
Cc: seanjc@...gle.com,
Yan Zhao <yan.y.zhao@...el.com>,
Rick Edgecombe <rick.p.edgecombe@...el.com>,
Isaku Yamahata <isaku.yamahata@...el.com>,
Adrian Hunter <adrian.hunter@...el.com>
Subject: [PATCH 23/29] KVM: TDX: Finalize VM initialization
From: Isaku Yamahata <isaku.yamahata@...el.com>
Add a new VM-scoped KVM_MEMORY_ENCRYPT_OP IOCTL subcommand,
KVM_TDX_FINALIZE_VM, to perform TD Measurement Finalization.
Documentation for the API is added in another patch:
"Documentation/virt/kvm: Document on Trust Domain Extensions(TDX)"
For the purpose of attestation, a measurement must be made of the TDX VM
initial state. This is referred to as TD Measurement Finalization, and
uses SEAMCALL TDH.MR.FINALIZE, after which:
1. The VMM adding TD private pages with arbitrary content is no longer
allowed
2. The TDX VM is runnable
Co-developed-by: Adrian Hunter <adrian.hunter@...el.com>
Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
Message-ID: <20240904030751.117579-21-rick.p.edgecombe@...el.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
arch/x86/include/uapi/asm/kvm.h | 1 +
arch/x86/kvm/vmx/tdx.c | 78 +++++++++++++++++++++++++++++----
arch/x86/kvm/vmx/tdx.h | 3 ++
3 files changed, 74 insertions(+), 8 deletions(-)
diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
index ee1b517351a3..89cc7a18ef45 100644
--- a/arch/x86/include/uapi/asm/kvm.h
+++ b/arch/x86/include/uapi/asm/kvm.h
@@ -933,6 +933,7 @@ enum kvm_tdx_cmd_id {
KVM_TDX_INIT_VM,
KVM_TDX_INIT_VCPU,
KVM_TDX_INIT_MEM_REGION,
+ KVM_TDX_FINALIZE_VM,
KVM_TDX_GET_CPUID,
KVM_TDX_CMD_NR_MAX,
diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index 12f3433d062d..246f924ae6f6 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -557,6 +557,29 @@ static int tdx_mem_page_aug(struct kvm *kvm, gfn_t gfn,
return 0;
}
+/*
+ * KVM_TDX_INIT_MEM_REGION calls kvm_gmem_populate() to map guest pages; the
+ * callback tdx_gmem_post_populate() then maps pages into private memory.
+ * through the a seamcall TDH.MEM.PAGE.ADD(). The SEAMCALL also requires the
+ * private EPT structures for the page to have been built before, which is
+ * done via kvm_tdp_map_page(). nr_premapped counts the number of pages that
+ * were added to the EPT structures but not added with TDH.MEM.PAGE.ADD().
+ * The counter has to be zero on KVM_TDX_FINALIZE_VM, to ensure that there
+ * are no half-initialized shared EPT pages.
+ */
+static int tdx_mem_page_record_premap_cnt(struct kvm *kvm, gfn_t gfn,
+ enum pg_level level, kvm_pfn_t pfn)
+{
+ struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm);
+
+ if (KVM_BUG_ON(kvm->arch.pre_fault_allowed, kvm))
+ return -EINVAL;
+
+ /* nr_premapped will be decreased when tdh_mem_page_add() is called. */
+ atomic64_inc(&kvm_tdx->nr_premapped);
+ return 0;
+}
+
int tdx_sept_set_private_spte(struct kvm *kvm, gfn_t gfn,
enum pg_level level, kvm_pfn_t pfn)
{
@@ -577,14 +600,15 @@ int tdx_sept_set_private_spte(struct kvm *kvm, gfn_t gfn,
*/
get_page(page);
+ /*
+ * Read 'pre_fault_allowed' before 'kvm_tdx->state'; see matching
+ * barrier in tdx_td_finalize().
+ */
+ smp_rmb();
if (likely(kvm_tdx->state == TD_STATE_RUNNABLE))
return tdx_mem_page_aug(kvm, gfn, level, page);
- /*
- * TODO: KVM_TDX_INIT_MEM_REGION support to populate before finalize
- * comes here for the initial memory.
- */
- return -EOPNOTSUPP;
+ return tdx_mem_page_record_premap_cnt(kvm, gfn, level, pfn);
}
static int tdx_sept_drop_private_spte(struct kvm *kvm, gfn_t gfn,
@@ -615,10 +639,12 @@ static int tdx_sept_drop_private_spte(struct kvm *kvm, gfn_t gfn,
if (unlikely(kvm_tdx->state != TD_STATE_RUNNABLE &&
err == (TDX_EPT_WALK_FAILED | TDX_OPERAND_ID_RCX))) {
/*
- * This page was mapped with KVM_MAP_MEMORY, but
- * KVM_TDX_INIT_MEM_REGION is not issued yet.
+ * Page is mapped by KVM_TDX_INIT_MEM_REGION, but hasn't called
+ * tdh_mem_page_add().
*/
- if (!is_last_spte(entry, level) || !(entry & VMX_EPT_RWX_MASK)) {
+ if ((!is_last_spte(entry, level) || !(entry & VMX_EPT_RWX_MASK)) &&
+ !KVM_BUG_ON(!atomic64_read(&kvm_tdx->nr_premapped), kvm)) {
+ atomic64_dec(&kvm_tdx->nr_premapped);
tdx_unpin(kvm, page);
return 0;
}
@@ -1365,6 +1391,36 @@ void tdx_flush_tlb_all(struct kvm_vcpu *vcpu)
ept_sync_global();
}
+static int tdx_td_finalize(struct kvm *kvm, struct kvm_tdx_cmd *cmd)
+{
+ struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm);
+
+ guard(mutex)(&kvm->slots_lock);
+
+ if (!is_hkid_assigned(kvm_tdx) || kvm_tdx->state == TD_STATE_RUNNABLE)
+ return -EINVAL;
+ /*
+ * Pages are pending for KVM_TDX_INIT_MEM_REGION to issue
+ * TDH.MEM.PAGE.ADD().
+ */
+ if (atomic64_read(&kvm_tdx->nr_premapped))
+ return -EINVAL;
+
+ cmd->hw_error = tdh_mr_finalize(&kvm_tdx->td);
+ if (tdx_operand_busy(cmd->hw_error))
+ return -EBUSY;
+ if (KVM_BUG_ON(cmd->hw_error, kvm)) {
+ pr_tdx_error(TDH_MR_FINALIZE, cmd->hw_error);
+ return -EIO;
+ }
+
+ kvm_tdx->state = TD_STATE_RUNNABLE;
+ /* TD_STATE_RUNNABLE must be set before 'pre_fault_allowed' */
+ smp_wmb();
+ kvm->arch.pre_fault_allowed = true;
+ return 0;
+}
+
int tdx_vm_ioctl(struct kvm *kvm, void __user *argp)
{
struct kvm_tdx_cmd tdx_cmd;
@@ -1389,6 +1445,9 @@ int tdx_vm_ioctl(struct kvm *kvm, void __user *argp)
case KVM_TDX_INIT_VM:
r = tdx_td_init(kvm, &tdx_cmd);
break;
+ case KVM_TDX_FINALIZE_VM:
+ r = tdx_td_finalize(kvm, &tdx_cmd);
+ break;
default:
r = -EINVAL;
goto out;
@@ -1656,6 +1715,9 @@ static int tdx_gmem_post_populate(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn,
goto out;
}
+ if (!KVM_BUG_ON(!atomic64_read(&kvm_tdx->nr_premapped), kvm))
+ atomic64_dec(&kvm_tdx->nr_premapped);
+
if (arg->flags & KVM_TDX_MEASURE_MEMORY_REGION) {
for (i = 0; i < PAGE_SIZE; i += TDX_EXTENDMR_CHUNKSIZE) {
err = tdh_mr_extend(&kvm_tdx->td, gpa + i, &entry,
diff --git a/arch/x86/kvm/vmx/tdx.h b/arch/x86/kvm/vmx/tdx.h
index 77d693dfcb08..b71f8e9643e4 100644
--- a/arch/x86/kvm/vmx/tdx.h
+++ b/arch/x86/kvm/vmx/tdx.h
@@ -31,6 +31,9 @@ struct kvm_tdx {
u64 tsc_offset;
struct tdx_td td;
+
+ /* For KVM_TDX_INIT_MEM_REGION. */
+ atomic64_t nr_premapped;
};
/* TDX module vCPU states */
--
2.43.5
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