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Date: Mon, 19 Feb 2024 16:54:27 +0800
From: Binbin Wu <binbin.wu@...ux.intel.com>
To: isaku.yamahata@...el.com
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
isaku.yamahata@...il.com, Paolo Bonzini <pbonzini@...hat.com>,
erdemaktas@...gle.com, Sean Christopherson <seanjc@...gle.com>,
Sagi Shahar <sagis@...gle.com>, Kai Huang <kai.huang@...el.com>,
chen.bo@...el.com, hang.yuan@...el.com, tina.zhang@...el.com,
gkirkpatrick@...gle.com
Subject: Re: [PATCH v18 064/121] KVM: TDX: Create initial guest memory
On 1/23/2024 7:53 AM, isaku.yamahata@...el.com wrote:
> From: Isaku Yamahata <isaku.yamahata@...el.com>
>
> Because the guest memory is protected in TDX, the creation of the initial
> guest memory requires a dedicated TDX module API, tdh_mem_page_add, instead
> of directly copying the memory contents into the guest memory in the case
> of the default VM type. KVM MMU page fault handler callback,
> private_page_add, handles it.
The changelog is stale? Do you mean "set_private_spte"?
>
> Define new subcommand, KVM_TDX_INIT_MEM_REGION, of VM-scoped
> KVM_MEMORY_ENCRYPT_OP. It assigns the guest page, copies the initial
> memory contents into the guest memory, encrypts the guest memory. At the
> same time, optionally it extends memory measurement of the TDX guest. It
> calls the KVM MMU page fault(EPT-violation) handler to trigger the
> callbacks for it.
>
> Reported-by: gkirkpatrick@...gle.com
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
>
> ---
> v18:
> - rename tdx_sept_page_add() -> tdx_mem_page_add().
> - open code tdx_measure_page() into tdx_mem_page_add().
> - remove the change of tools/arch/x86/include/uapi/asm/kvm.h.
>
> v15 -> v16:
> - add check if nr_pages isn't large with
> (nr_page << PAGE_SHIFT) >> PAGE_SHIFT
>
> v14 -> v15:
> - add a check if TD is finalized or not to tdx_init_mem_region()
> - return -EAGAIN when partial population
> ---
> arch/x86/include/uapi/asm/kvm.h | 9 ++
> arch/x86/kvm/mmu/mmu.c | 1 +
> arch/x86/kvm/vmx/tdx.c | 160 +++++++++++++++++++++++++++++++-
> arch/x86/kvm/vmx/tdx.h | 2 +
> 4 files changed, 169 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
> index 4000a2e087a8..9fda7c90b7b5 100644
> --- a/arch/x86/include/uapi/asm/kvm.h
> +++ b/arch/x86/include/uapi/asm/kvm.h
> @@ -572,6 +572,7 @@ enum kvm_tdx_cmd_id {
> KVM_TDX_CAPABILITIES = 0,
> KVM_TDX_INIT_VM,
> KVM_TDX_INIT_VCPU,
> + KVM_TDX_INIT_MEM_REGION,
>
> KVM_TDX_CMD_NR_MAX,
> };
> @@ -649,4 +650,12 @@ struct kvm_tdx_init_vm {
> struct kvm_cpuid2 cpuid;
> };
>
> +#define KVM_TDX_MEASURE_MEMORY_REGION (1UL << 0)
> +
> +struct kvm_tdx_init_mem_region {
> + __u64 source_addr;
> + __u64 gpa;
> + __u64 nr_pages;
> +};
> +
> #endif /* _ASM_X86_KVM_H */
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 26d215e85b76..fc258f112e73 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -5663,6 +5663,7 @@ int kvm_mmu_load(struct kvm_vcpu *vcpu)
> out:
> return r;
> }
> +EXPORT_SYMBOL(kvm_mmu_load);
>
> void kvm_mmu_unload(struct kvm_vcpu *vcpu)
> {
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index 4cbcedff4f16..1a5a91b99de9 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -591,6 +591,69 @@ static int tdx_mem_page_aug(struct kvm *kvm, gfn_t gfn,
> return 0;
> }
>
> +static int tdx_mem_page_add(struct kvm *kvm, gfn_t gfn,
> + enum pg_level level, kvm_pfn_t pfn)
> +{
> + struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm);
> + hpa_t hpa = pfn_to_hpa(pfn);
> + gpa_t gpa = gfn_to_gpa(gfn);
> + struct tdx_module_args out;
> + hpa_t source_pa;
> + bool measure;
> + u64 err;
> + int i;
> +
> + /*
> + * KVM_INIT_MEM_REGION, tdx_init_mem_region(), supports only 4K page
> + * because tdh_mem_page_add() supports only 4K page.
> + */
> + if (KVM_BUG_ON(level != PG_LEVEL_4K, kvm))
> + return -EINVAL;
> +
> + /*
> + * In case of TDP MMU, fault handler can run concurrently. Note
> + * 'source_pa' is a TD scope variable, meaning if there are multiple
> + * threads reaching here with all needing to access 'source_pa', it
> + * will break. However fortunately this won't happen, because below
> + * TDH_MEM_PAGE_ADD code path is only used when VM is being created
> + * before it is running, using KVM_TDX_INIT_MEM_REGION ioctl (which
> + * always uses vcpu 0's page table and protected by vcpu->mutex).
> + */
> + if (KVM_BUG_ON(kvm_tdx->source_pa == INVALID_PAGE, kvm)) {
> + tdx_unpin(kvm, pfn);
> + return -EINVAL;
> + }
> +
> + source_pa = kvm_tdx->source_pa & ~KVM_TDX_MEASURE_MEMORY_REGION;
> + measure = kvm_tdx->source_pa & KVM_TDX_MEASURE_MEMORY_REGION;
> + kvm_tdx->source_pa = INVALID_PAGE;
> +
> + do {
> + err = tdh_mem_page_add(kvm_tdx->tdr_pa, gpa, hpa, source_pa,
> + &out);
> + /*
> + * This path is executed during populating initial guest memory
> + * image. i.e. before running any vcpu. Race is rare.
> + */
> + } while (unlikely(err == TDX_ERROR_SEPT_BUSY));
For page add, since pages are added one by one, there should be no such
error, right?
> + if (KVM_BUG_ON(err, kvm)) {
> + pr_tdx_error(TDH_MEM_PAGE_ADD, err, &out);
> + tdx_unpin(kvm, pfn);
> + return -EIO;
> + } else if (measure) {
> + for (i = 0; i < PAGE_SIZE; i += TDX_EXTENDMR_CHUNKSIZE) {
> + err = tdh_mr_extend(kvm_tdx->tdr_pa, gpa + i, &out);
> + if (KVM_BUG_ON(err, &kvm_tdx->kvm)) {
> + pr_tdx_error(TDH_MR_EXTEND, err, &out);
> + break;
> + }
> + }
> + }
> +
> + return 0;
> +
> +}
> +
> static int tdx_sept_set_private_spte(struct kvm *kvm, gfn_t gfn,
> enum pg_level level, kvm_pfn_t pfn)
> {
> @@ -613,9 +676,7 @@ static int tdx_sept_set_private_spte(struct kvm *kvm, gfn_t gfn,
> if (likely(is_td_finalized(kvm_tdx)))
> return tdx_mem_page_aug(kvm, gfn, level, pfn);
>
> - /* TODO: tdh_mem_page_add() comes here for the initial memory. */
> -
> - return 0;
> + return tdx_mem_page_add(kvm, gfn, level, pfn);
> }
>
> static int tdx_sept_drop_private_spte(struct kvm *kvm, gfn_t gfn,
> @@ -1322,6 +1383,96 @@ void tdx_flush_tlb_current(struct kvm_vcpu *vcpu)
> tdx_track(vcpu->kvm);
> }
>
> +#define TDX_SEPT_PFERR (PFERR_WRITE_MASK | PFERR_GUEST_ENC_MASK)
> +
> +static int tdx_init_mem_region(struct kvm *kvm, struct kvm_tdx_cmd *cmd)
> +{
> + struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm);
> + struct kvm_tdx_init_mem_region region;
> + struct kvm_vcpu *vcpu;
> + struct page *page;
> + int idx, ret = 0;
> + bool added = false;
> +
> + /* Once TD is finalized, the initial guest memory is fixed. */
> + if (is_td_finalized(kvm_tdx))
> + return -EINVAL;
> +
> + /* The BSP vCPU must be created before initializing memory regions. */
> + if (!atomic_read(&kvm->online_vcpus))
> + return -EINVAL;
> +
> + if (cmd->flags & ~KVM_TDX_MEASURE_MEMORY_REGION)
> + return -EINVAL;
> +
> + if (copy_from_user(®ion, (void __user *)cmd->data, sizeof(region)))
> + return -EFAULT;
> +
> + /* Sanity check */
> + if (!IS_ALIGNED(region.source_addr, PAGE_SIZE) ||
> + !IS_ALIGNED(region.gpa, PAGE_SIZE) ||
> + !region.nr_pages ||
> + region.nr_pages & GENMASK_ULL(63, 63 - PAGE_SHIFT) ||
> + region.gpa + (region.nr_pages << PAGE_SHIFT) <= region.gpa ||
> + !kvm_is_private_gpa(kvm, region.gpa) ||
> + !kvm_is_private_gpa(kvm, region.gpa + (region.nr_pages << PAGE_SHIFT)))
> + return -EINVAL;
> +
> + vcpu = kvm_get_vcpu(kvm, 0);
> + if (mutex_lock_killable(&vcpu->mutex))
> + return -EINTR;
> +
> + vcpu_load(vcpu);
> + idx = srcu_read_lock(&kvm->srcu);
> +
> + kvm_mmu_reload(vcpu);
> +
> + while (region.nr_pages) {
> + if (signal_pending(current)) {
> + ret = -ERESTARTSYS;
> + break;
> + }
> +
> + if (need_resched())
> + cond_resched();
> +
> + /* Pin the source page. */
> + ret = get_user_pages_fast(region.source_addr, 1, 0, &page);
> + if (ret < 0)
> + break;
> + if (ret != 1) {
> + ret = -ENOMEM;
> + break;
> + }
> +
> + kvm_tdx->source_pa = pfn_to_hpa(page_to_pfn(page)) |
> + (cmd->flags & KVM_TDX_MEASURE_MEMORY_REGION);
> +
> + ret = kvm_mmu_map_tdp_page(vcpu, region.gpa, TDX_SEPT_PFERR,
> + PG_LEVEL_4K);
> + put_page(page);
> + if (ret)
> + break;
> +
> + region.source_addr += PAGE_SIZE;
> + region.gpa += PAGE_SIZE;
> + region.nr_pages--;
> + added = true;
> + }
> +
> + srcu_read_unlock(&kvm->srcu, idx);
> + vcpu_put(vcpu);
> +
> + mutex_unlock(&vcpu->mutex);
> +
> + if (added && region.nr_pages > 0)
> + ret = -EAGAIN;
> + if (copy_to_user((void __user *)cmd->data, ®ion, sizeof(region)))
> + ret = -EFAULT;
> +
> + return ret;
> +}
> +
> int tdx_vm_ioctl(struct kvm *kvm, void __user *argp)
> {
> struct kvm_tdx_cmd tdx_cmd;
> @@ -1341,6 +1492,9 @@ 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_INIT_MEM_REGION:
> + r = tdx_init_mem_region(kvm, &tdx_cmd);
> + break;
> default:
> r = -EINVAL;
> goto out;
> diff --git a/arch/x86/kvm/vmx/tdx.h b/arch/x86/kvm/vmx/tdx.h
> index 783ce329d7da..d589a2caedfb 100644
> --- a/arch/x86/kvm/vmx/tdx.h
> +++ b/arch/x86/kvm/vmx/tdx.h
> @@ -17,6 +17,8 @@ struct kvm_tdx {
> u64 xfam;
> int hkid;
>
> + hpa_t source_pa;
> +
> bool finalized;
> atomic_t tdh_mem_track;
>
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