Re: [PATCH RESEND v4 5/9] KVM: VMX: Add init/set/get functions for SPP

Paolo Bonzini
2019-08-19T15:13:53Z

On 14/08/19 09:03, Yang Weijiang wrote:
> init_spp() must be called before {get, set}_subpage
> functions, it creates subpage access bitmaps for memory pages
> and issues a KVM request to setup SPPT root pages.
>
> kvm_mmu_set_subpages() is to enable SPP bit in EPT leaf page
> and setup corresponding SPPT entries. The mmu_lock
> is held before above operation. If it's called in EPT fault and
> SPPT mis-config induced handler, mmu_lock is acquired outside
> the function, otherwise, it's acquired inside it.
>
> kvm_mmu_get_subpages() is used to query access bitmap for
> protected page, it's also used in EPT fault handler to check
> whether the fault EPT page is SPP protected as well.
>
> Co-developed-by: He Chen <he.chen@linux.intel.com>
> Signed-off-by: He Chen <he.chen@linux.intel.com>
> Co-developed-by: Zhang Yi <yi.z.zhang@linux.intel.com>
> Signed-off-by: Zhang Yi <yi.z.zhang@linux.intel.com>
> Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
> ---
> arch/x86/include/asm/kvm_host.h | 18 ++++
> arch/x86/include/asm/vmx.h | 2 +
> arch/x86/kvm/mmu.c | 160 ++++++++++++++++++++++++++++++++
> arch/x86/kvm/vmx/vmx.c | 48 ++++++++++
> arch/x86/kvm/x86.c | 40 ++++++++
> include/linux/kvm_host.h | 4 +-
> include/uapi/linux/kvm.h | 9 ++
> 7 files changed, 280 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 44f6e1757861..5c4882015acc 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -398,8 +398,13 @@ struct kvm_mmu {
> void (*invlpg)(struct kvm_vcpu *vcpu, gva_t gva, hpa_t root_hpa);
> void (*update_pte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
> u64 *spte, const void *pte);
> + int (*get_subpages)(struct kvm *kvm, struct kvm_subpage *spp_info);
> + int (*set_subpages)(struct kvm *kvm, struct kvm_subpage *spp_info);
> + int (*init_spp)(struct kvm *kvm);
> +
> hpa_t root_hpa;
> gpa_t root_cr3;
> + hpa_t sppt_root;
> union kvm_mmu_role mmu_role;
> u8 root_level;
> u8 shadow_root_level;
> @@ -927,6 +932,8 @@ struct kvm_arch {
>
> bool guest_can_read_msr_platform_info;
> bool exception_payload_enabled;
> +
> + bool spp_active;
> };
>
> struct kvm_vm_stat {
> @@ -1199,6 +1206,11 @@ struct kvm_x86_ops {
> uint16_t (*nested_get_evmcs_version)(struct kvm_vcpu *vcpu);
>
> bool (*need_emulation_on_page_fault)(struct kvm_vcpu *vcpu);
> +
> + bool (*get_spp_status)(void);
> + int (*get_subpages)(struct kvm *kvm, struct kvm_subpage *spp_info);
> + int (*set_subpages)(struct kvm *kvm, struct kvm_subpage *spp_info);
> + int (*init_spp)(struct kvm *kvm);
> };
>
> struct kvm_arch_async_pf {
> @@ -1417,6 +1429,12 @@ void kvm_mmu_invlpg(struct kvm_vcpu *vcpu, gva_t gva);
> void kvm_mmu_invpcid_gva(struct kvm_vcpu *vcpu, gva_t gva, unsigned long pcid);
> void kvm_mmu_new_cr3(struct kvm_vcpu *vcpu, gpa_t new_cr3, bool skip_tlb_flush);
>
> +int kvm_mmu_get_subpages(struct kvm *kvm, struct kvm_subpage *spp_info,
> + bool mmu_locked);
> +int kvm_mmu_set_subpages(struct kvm *kvm, struct kvm_subpage *spp_info,
> + bool mmu_locked);
> +int kvm_mmu_init_spp(struct kvm *kvm);
> +
> void kvm_enable_tdp(void);
> void kvm_disable_tdp(void);
>
> diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
> index a2c9e18e0ad7..6cb05ac07453 100644
> --- a/arch/x86/include/asm/vmx.h
> +++ b/arch/x86/include/asm/vmx.h
> @@ -224,6 +224,8 @@ enum vmcs_field {
> XSS_EXIT_BITMAP_HIGH = 0x0000202D,
> ENCLS_EXITING_BITMAP = 0x0000202E,
> ENCLS_EXITING_BITMAP_HIGH = 0x0000202F,
> + SPPT_POINTER = 0x00002030,
> + SPPT_POINTER_HIGH = 0x00002031,
> TSC_MULTIPLIER = 0x00002032,
> TSC_MULTIPLIER_HIGH = 0x00002033,
> GUEST_PHYSICAL_ADDRESS = 0x00002400,
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 16e390fd6e58..16d3ca544b67 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -3756,6 +3756,9 @@ void kvm_mmu_free_roots(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
> (mmu->root_level >= PT64_ROOT_4LEVEL || mmu->direct_map)) {
> mmu_free_root_page(vcpu->kvm, &mmu->root_hpa,
> &invalid_list);
> + if (vcpu->kvm->arch.spp_active)
> + mmu_free_root_page(vcpu->kvm, &mmu->sppt_root,
> + &invalid_list);
> } else {
> for (i = 0; i < 4; ++i)
> if (mmu->pae_root[i] != 0)
> @@ -4414,6 +4417,158 @@ int kvm_mmu_setup_spp_structure(struct kvm_vcpu *vcpu,
> return ret;
> }
> EXPORT_SYMBOL_GPL(kvm_mmu_setup_spp_structure);
> +
> +int kvm_mmu_init_spp(struct kvm *kvm)
> +{
> + int i, ret;
> + struct kvm_vcpu *vcpu;
> + int root_level;
> + struct kvm_mmu_page *ssp_sp;
> +
> +
> + if (!kvm_x86_ops->get_spp_status())
> + return -ENODEV;
> +
> + if (kvm->arch.spp_active)
> + return 0;
> +
> + ret = kvm_subpage_create_bitmaps(kvm);
> +
> + if (ret)
> + return ret;
> +
> + kvm_for_each_vcpu(i, vcpu, kvm) {
> + /* prepare caches for SPP setup.*/
> + mmu_topup_memory_caches(vcpu);
> + root_level = vcpu->arch.mmu->shadow_root_level;
> + ssp_sp = kvm_mmu_get_spp_page(vcpu, 0, root_level);
> + ++ssp_sp->root_count;
> + vcpu->arch.mmu->sppt_root = __pa(ssp_sp->spt);
> + kvm_make_request(KVM_REQ_LOAD_CR3, vcpu);
> + }
> +
> + kvm->arch.spp_active = true;
> + return 0;
> +}
> +
> +int kvm_mmu_get_subpages(struct kvm *kvm, struct kvm_subpage *spp_info,
> + bool mmu_locked)
> +{
> + u32 *access = spp_info->access_map;
> + gfn_t gfn = spp_info->base_gfn;
> + int npages = spp_info->npages;
> + struct kvm_memory_slot *slot;
> + int i;
> + int ret;
> +
> + if (!kvm->arch.spp_active)
> + return -ENODEV;
> +
> + if (!mmu_locked)
> + spin_lock(&kvm->mmu_lock);
> +
> + for (i = 0; i < npages; i++, gfn++) {
> + slot = gfn_to_memslot(kvm, gfn);
> + if (!slot) {
> + ret = -EFAULT;
> + goto out_unlock;
> + }
> + access[i] = *gfn_to_subpage_wp_info(slot, gfn);
> + }
> +
> + ret = i;
> +
> +out_unlock:
> + if (!mmu_locked)
> + spin_unlock(&kvm->mmu_lock);
> +
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(kvm_mmu_get_subpages);
> +
> +int kvm_mmu_set_subpages(struct kvm *kvm, struct kvm_subpage *spp_info,
> + bool mmu_locked)
> +{
> + u32 *access = spp_info->access_map;
> + gfn_t gfn = spp_info->base_gfn;
> + int npages = spp_info->npages;
> + struct kvm_memory_slot *slot;
> + struct kvm_vcpu *vcpu;
> + struct kvm_rmap_head *rmap_head;
> + int i, k;
> + u32 *wp_map;
> + int ret = -EFAULT;
> +
> + if (!kvm->arch.spp_active)
> + return -ENODEV;
> +
> + if (!mmu_locked)
> + spin_lock(&kvm->mmu_lock);
> +
> + for (i = 0; i < npages; i++, gfn++) {
> + slot = gfn_to_memslot(kvm, gfn);
> + if (!slot)
> + goto out_unlock;
> +
> + /*
> + * check whether the target 4KB page exists in EPT leaf
> + * entries.If it's there, we can setup SPP protection now,
> + * otherwise, need to defer it to EPT page fault handler.
> + */
> + rmap_head = __gfn_to_rmap(gfn, PT_PAGE_TABLE_LEVEL, slot);
> +
> + if (rmap_head->val) {
> + /*
> + * if all subpages are not writable, open SPP bit in
> + * EPT leaf entry to enable SPP protection for
> + * corresponding page.
> + */
> + if (access[i] != FULL_SPP_ACCESS) {
> + ret = kvm_mmu_open_subpage_write_protect(kvm,
> + slot, gfn);
> +
> + if (ret)
> + goto out_err;
> +
> + kvm_for_each_vcpu(k, vcpu, kvm)
> + kvm_mmu_setup_spp_structure(vcpu,
> + access[i], gfn);
> + } else {
> + ret = kvm_mmu_clear_subpage_write_protect(kvm,
> + slot, gfn);
> + if (ret)
> + goto out_err;
> + }
> +
> + } else
> + pr_info("%s - No ETP entry, gfn = 0x%llx, access = 0x%x.\n", __func__, gfn, access[i]);
> +
> + /* if this function is called in tdp_page_fault() or
> + * spp_handler(), mmu_locked = true, SPP access bitmap
> + * is being used, otherwise, it's being stored.
> + */
> + if (!mmu_locked) {
> + wp_map = gfn_to_subpage_wp_info(slot, gfn);
> + *wp_map = access[i];
> + }
> + }
> +
> + ret = i;
> +out_err:
> + if (ret < 0)
> + pr_info("SPP-Error, didn't get the gfn:" \
> + "%llx from EPT leaf.\n"
> + "Current we don't support SPP on" \
> + "huge page.\n"
> + "Please disable huge page and have" \
> + "another try.\n", gfn);
> +out_unlock:
> + if (!mmu_locked)
> + spin_unlock(&kvm->mmu_lock);
> +
> + return ret;
> +}
> +
> static void nonpaging_init_context(struct kvm_vcpu *vcpu,
> struct kvm_mmu *context)
> {
> @@ -5104,6 +5259,9 @@ static void init_kvm_tdp_mmu(struct kvm_vcpu *vcpu)
> context->get_cr3 = get_cr3;
> context->get_pdptr = kvm_pdptr_read;
> context->inject_page_fault = kvm_inject_page_fault;
> + context->get_subpages = kvm_x86_ops->get_subpages;
> + context->set_subpages = kvm_x86_ops->set_subpages;
> + context->init_spp = kvm_x86_ops->init_spp;
>
> if (!is_paging(vcpu)) {
> context->nx = false;
> @@ -5309,6 +5467,8 @@ void kvm_init_mmu(struct kvm_vcpu *vcpu, bool reset_roots)
> uint i;
>
> vcpu->arch.mmu->root_hpa = INVALID_PAGE;
> + if (!vcpu->kvm->arch.spp_active)
> + vcpu->arch.mmu->sppt_root = INVALID_PAGE;
>
> for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++)
> vcpu->arch.mmu->prev_roots[i] = KVM_MMU_ROOT_INFO_INVALID;
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index a0753a36155d..855d02dd94c7 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -2847,11 +2847,17 @@ u64 construct_eptp(struct kvm_vcpu *vcpu, unsigned long root_hpa)
> return eptp;
> }
>
> +static inline u64 construct_spptp(unsigned long root_hpa)
> +{
> + return root_hpa & PAGE_MASK;
> +}
> +
> void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
> {
> struct kvm *kvm = vcpu->kvm;
> unsigned long guest_cr3;
> u64 eptp;
> + u64 spptp;
>
> guest_cr3 = cr3;
> if (enable_ept) {
> @@ -2874,6 +2880,12 @@ void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
> ept_load_pdptrs(vcpu);
> }
>
> + if (kvm->arch.spp_active && VALID_PAGE(vcpu->arch.mmu->sppt_root)) {
> + spptp = construct_spptp(vcpu->arch.mmu->sppt_root);
> + vmcs_write64(SPPT_POINTER, spptp);
> + vmx_flush_tlb(vcpu, true);
> + }
> +
> vmcs_writel(GUEST_CR3, guest_cr3);
> }
>
> @@ -5735,6 +5747,9 @@ void dump_vmcs(void)
> pr_err("PostedIntrVec = 0x%02x\n", vmcs_read16(POSTED_INTR_NV));
> if ((secondary_exec_control & SECONDARY_EXEC_ENABLE_EPT))
> pr_err("EPT pointer = 0x%016llx\n", vmcs_read64(EPT_POINTER));
> + if ((secondary_exec_control & SECONDARY_EXEC_ENABLE_SPP))
> + pr_err("SPPT pointer = 0x%016llx\n", vmcs_read64(SPPT_POINTER));
> +
> n = vmcs_read32(CR3_TARGET_COUNT);
> for (i = 0; i + 1 < n; i += 4)
> pr_err("CR3 target%u=%016lx target%u=%016lx\n",
> @@ -7546,6 +7561,12 @@ static __init int hardware_setup(void)
> kvm_x86_ops->enable_log_dirty_pt_masked = NULL;
> }
>
> + if (!spp_supported) {
> + kvm_x86_ops->get_subpages = NULL;
> + kvm_x86_ops->set_subpages = NULL;
> + kvm_x86_ops->init_spp = NULL;
> + }
> +
> if (!cpu_has_vmx_preemption_timer())
> kvm_x86_ops->request_immediate_exit = __kvm_request_immediate_exit;
>
> @@ -7592,6 +7613,28 @@ static __exit void hardware_unsetup(void)
> free_kvm_area();
> }
>
> +static bool vmx_get_spp_status(void)
> +{
> + return spp_supported;
> +}
> +
> +static int vmx_get_subpages(struct kvm *kvm,
> + struct kvm_subpage *spp_info)
> +{
> + return kvm_get_subpages(kvm, spp_info);
> +}
> +
> +static int vmx_set_subpages(struct kvm *kvm,
> + struct kvm_subpage *spp_info)
> +{
> + return kvm_set_subpages(kvm, spp_info);
> +}
> +
> +static int vmx_init_spp(struct kvm *kvm)
> +{
> + return kvm_init_spp(kvm);
> +}
> +
> static struct kvm_x86_ops vmx_x86_ops __ro_after_init = {
> .cpu_has_kvm_support = cpu_has_kvm_support,
> .disabled_by_bios = vmx_disabled_by_bios,
> @@ -7740,6 +7783,11 @@ static struct kvm_x86_ops vmx_x86_ops __ro_after_init = {
> .get_vmcs12_pages = NULL,
> .nested_enable_evmcs = NULL,
> .need_emulation_on_page_fault = vmx_need_emulation_on_page_fault,
> +
> + .get_spp_status = vmx_get_spp_status,
> + .get_subpages = vmx_get_subpages,
> + .set_subpages = vmx_set_subpages,
> + .init_spp = vmx_init_spp,
> };

There's no need for the get_subpages kvm_x86_ops. You do need init_spp
of course, but you do not need get_spp_status either; instead you can
check if init_spp is NULL (if NULL, SPP is not supported).

In addition, kvm_mmu_set_subpages should not set up the SPP pages. This
should be handled entirely by handle_spp when the processor reports an
SPPT miss, so you do not need that callback either. You may need a
flush_subpages callback, called by kvm_mmu_set_subpages to clear the SPP
page tables for a given GPA range. The next access then will cause an
SPPT miss.

Finally, please move all SPP-related code to arch/x86/kvm/vmx/{spp.c,spp.h}.

Thanks,

Paolo

> static void vmx_cleanup_l1d_flush(void)
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 26e4c574731c..c7cb17941344 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -4589,6 +4589,44 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
> return r;
> }
>
> +int kvm_get_subpages(struct kvm *kvm,
> + struct kvm_subpage *spp_info)
> +{
> + int ret;
> +
> + mutex_lock(&kvm->slots_lock);
> + ret = kvm_mmu_get_subpages(kvm, spp_info, false);
> + mutex_unlock(&kvm->slots_lock);
> +
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(kvm_get_subpages);
> +
> +int kvm_set_subpages(struct kvm *kvm,
> + struct kvm_subpage *spp_info)
> +{
> + int ret;
> +
> + mutex_lock(&kvm->slots_lock);
> + ret = kvm_mmu_set_subpages(kvm, spp_info, false);
> + mutex_unlock(&kvm->slots_lock);
> +
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(kvm_set_subpages);
> +
> +int kvm_init_spp(struct kvm *kvm)
> +{
> + int ret;
> +
> + mutex_lock(&kvm->slots_lock);
> + ret = kvm_mmu_init_spp(kvm);
> + mutex_unlock(&kvm->slots_lock);
> +
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(kvm_init_spp);
> +
> long kvm_arch_vm_ioctl(struct file *filp,
> unsigned int ioctl, unsigned long arg)
> {
> @@ -9349,6 +9387,8 @@ void kvm_arch_free_memslot(struct kvm *kvm, struct kvm_memory_slot *free,
> }
>
> kvm_page_track_free_memslot(free, dont);
> + if (kvm->arch.spp_active)
> + kvm_subpage_free_memslot(free, dont);
> }
>
> int kvm_arch_create_memslot(struct kvm *kvm, struct kvm_memory_slot *slot,
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 7f904d4d788c..da30fcbb2727 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -849,7 +849,9 @@ int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu);
>
> struct kvm_mmu_page *kvm_mmu_get_spp_page(struct kvm_vcpu *vcpu,
> gfn_t gfn, unsigned int level);
> -
> +int kvm_get_subpages(struct kvm *kvm, struct kvm_subpage *spp_info);
> +int kvm_set_subpages(struct kvm *kvm, struct kvm_subpage *spp_info);
> +int kvm_init_spp(struct kvm *kvm);
> #ifndef __KVM_HAVE_ARCH_VM_ALLOC
> /*
> * All architectures that want to use vzalloc currently also
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 6d4ea4b6c922..2c75a87ab3b5 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -102,6 +102,15 @@ struct kvm_userspace_memory_region {
> __u64 userspace_addr; /* start of the userspace allocated memory */
> };
>
> +/* for KVM_SUBPAGES_GET_ACCESS and KVM_SUBPAGES_SET_ACCESS */
> +#define SUBPAGE_MAX_BITMAP 64
> +struct kvm_subpage {
> + __u64 base_gfn;
> + __u64 npages;
> + /* sub-page write-access bitmap array */
> + __u32 access_map[SUBPAGE_MAX_BITMAP];
> +};
> +
> /*
> * The bit 0 ~ bit 15 of kvm_memory_region::flags are visible for userspace,
> * other bits are reserved for kvm internal use which are defined in
>