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KVM: TDX: Finalize VM initialization

Browse source 
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@intel.com>
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Message-ID: <20240904030751.117579-21-rick.p.edgecombe@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Isaku Yamahata 2024-09-03 20:07:50 -07:00 • committed by Paolo Bonzini
parent c846b451d3
commit 012426d6f5
3 changed files with 74 additions and 8 deletions
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1
arch/x86/include/uapi/asm/kvm.h
View file

@ -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,

78
arch/x86/kvm/vmx/tdx.c
View file

@ -562,6 +562,29 @@ 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)
{
@ -582,14 +605,15 @@ 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,
@ -620,10 +644,12 @@ 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;
}
@ -1371,6 +1397,36 @@ 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;
@ -1395,6 +1451,9 @@ 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;
@ -1662,6 +1721,9 @@ 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,

3
arch/x86/kvm/vmx/tdx.h
View file

@ -32,6 +32,9 @@ struct kvm_tdx {
u64 tsc_multiplier;
struct tdx_td td;
/* For KVM_TDX_INIT_MEM_REGION. */
atomic64_t nr_premapped;
};
/* TDX module vCPU states */