[PATCH v10 04/10] mmu: spp: Add functions to operate SPP access bitmap

Yang Weijiang
2019-12-31T06:46:55Z

Create access bitmap for SPP subpages, the bitmap can
be accessed with a gfn. The initial access bitmap for each
physical page is 0xFFFFFFFF, meaning SPP is not enabled for the
subpages.

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 | 2 +
arch/x86/kvm/mmu/spp.c | 332 ++++++++++++++++++++++++++++++++
arch/x86/kvm/mmu/spp.h | 12 ++
include/uapi/linux/kvm.h | 8 +
4 files changed, 354 insertions(+)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 9506c9d40895..f5145b86d620 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -812,6 +812,7 @@ struct kvm_lpage_info {

struct kvm_arch_memory_slot {
struct kvm_rmap_head *rmap[KVM_NR_PAGE_SIZES];
+ u32 *subpage_wp_info;
struct kvm_lpage_info *lpage_info[KVM_NR_PAGE_SIZES - 1];
unsigned short *gfn_track[KVM_PAGE_TRACK_MAX];
};
@@ -959,6 +960,7 @@ struct kvm_arch {
struct task_struct *nx_lpage_recovery_thread;

hpa_t sppt_root;
+ bool spp_active;
};

struct kvm_vm_stat {
diff --git a/arch/x86/kvm/mmu/spp.c b/arch/x86/kvm/mmu/spp.c
index 5fca08af705c..edf013102137 100644
--- a/arch/x86/kvm/mmu/spp.c
+++ b/arch/x86/kvm/mmu/spp.c
@@ -17,6 +17,21 @@ static void shadow_spp_walk_init(struct kvm_shadow_walk_iterator *iterator,
iterator->level = PT64_ROOT_4LEVEL;
}

+u32 *gfn_to_subpage_wp_info(struct kvm_memory_slot *slot, gfn_t gfn)
+{
+ unsigned long idx;
+
+ if (!slot->arch.subpage_wp_info)
+ return NULL;
+
+ idx = gfn_to_index(gfn, slot->base_gfn, PT_PAGE_TABLE_LEVEL);
+ if (idx > slot->npages - 1)
+ return NULL;
+
+ return &slot->arch.subpage_wp_info[idx];
+}
+EXPORT_SYMBOL_GPL(gfn_to_subpage_wp_info);
+
static bool __rmap_open_subpage_bit(struct kvm *kvm,
struct kvm_rmap_head *rmap_head)
{
@@ -172,6 +187,20 @@ bool is_spp_spte(struct kvm_mmu_page *sp)
return sp->role.spp;
}

+int kvm_spp_level_pages(gfn_t gfn_lower, gfn_t gfn_upper, int level)
+{
+ int page_num = KVM_PAGES_PER_HPAGE(level);
+ gfn_t gfn_max = (gfn_lower & ~(page_num - 1)) + page_num - 1;
+ int ret;
+
+ if (gfn_upper <= gfn_max)
+ ret = gfn_upper - gfn_lower + 1;
+ else
+ ret = gfn_max - gfn_lower + 1;
+
+ return ret;
+}
+
#define SPPT_ENTRY_PHA_MASK (0xFFFFFFFFFF << 12)

int kvm_spp_setup_structure(struct kvm_vcpu *vcpu,
@@ -220,6 +249,309 @@ int kvm_spp_setup_structure(struct kvm_vcpu *vcpu,
}
EXPORT_SYMBOL_GPL(kvm_spp_setup_structure);

+int vmx_spp_flush_sppt(struct kvm *kvm, u64 gfn_base, u32 npages)
+{
+ struct kvm_shadow_walk_iterator iter;
+ struct kvm_vcpu *vcpu;
+ gfn_t gfn = gfn_base;
+ gfn_t gfn_max = gfn_base + npages - 1;
+ u64 spde;
+ int count;
+ bool flush = false;
+
+ vcpu = kvm_get_vcpu(kvm, 0);
+ if (!VALID_PAGE(vcpu->kvm->arch.sppt_root))
+ return -EFAULT;
+
+ for (; gfn <= gfn_max; gfn++) {
+ for_each_shadow_spp_entry(vcpu, (u64)gfn << PAGE_SHIFT, iter) {
+ if (!is_shadow_present_pte(*iter.sptep))
+ break;
+
+ if (iter.level == PT_DIRECTORY_LEVEL) {
+ spde = *iter.sptep;
+ spde &= ~PT_PRESENT_MASK;
+ spp_spte_set(iter.sptep, spde);
+ count = kvm_spp_level_pages(gfn,
+ gfn_max,
+ PT_DIRECTORY_LEVEL);
+ flush = true;
+ if (count >= npages)
+ goto out;
+ gfn += count;
+ break;
+ }
+ }
+ }
+out:
+ if (flush)
+ kvm_flush_remote_tlbs(kvm);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(vmx_spp_flush_sppt);
+
+static int kvm_spp_create_bitmaps(struct kvm *kvm)
+{
+ struct kvm_memslots *slots;
+ struct kvm_memory_slot *memslot;
+ int i, j, ret;
+ u32 *buff;
+
+ for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
+ slots = __kvm_memslots(kvm, i);
+ kvm_for_each_memslot(memslot, slots) {
+ buff = kvzalloc(memslot->npages *
+ sizeof(*memslot->arch.subpage_wp_info),
+ GFP_KERNEL);
+
+ if (!buff) {
+ ret = -ENOMEM;
+ goto out_free;
+ }
+ memslot->arch.subpage_wp_info = buff;
+
+ for (j = 0; j < memslot->npages; j++)
+ buff[j] = FULL_SPP_ACCESS;
+ }
+ }
+
+ return 0;
+out_free:
+ for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
+ slots = __kvm_memslots(kvm, i);
+ kvm_for_each_memslot(memslot, slots) {
+ if (memslot->arch.subpage_wp_info) {
+ kvfree(memslot->arch.subpage_wp_info);
+ memslot->arch.subpage_wp_info = NULL;
+ }
+ }
+ }
+
+ return ret;
+}
+
+int vmx_spp_init(struct kvm *kvm)
+{
+ int i, ret;
+ struct kvm_vcpu *vcpu;
+ int root_level;
+ struct kvm_mmu_page *ssp_sp;
+ bool first_root = true;
+
+ /* SPP feature is exclusive with nested VM.*/
+ if (kvm_x86_ops->get_nested_state)
+ return -EPERM;
+
+ if (kvm->arch.spp_active)
+ return 0;
+
+ ret = kvm_spp_create_bitmaps(kvm);
+
+ if (ret)
+ return ret;
+
+ kvm_for_each_vcpu(i, vcpu, kvm) {
+ if (first_root) {
+ /* prepare caches for SPP setup.*/
+ mmu_topup_memory_caches(vcpu);
+ root_level = vcpu->arch.mmu->shadow_root_level;
+ ssp_sp = kvm_spp_get_page(vcpu, 0, root_level);
+ first_root = false;
+ vcpu->kvm->arch.sppt_root = __pa(ssp_sp->spt);
+ }
+ ++ssp_sp->root_count;
+ kvm_make_request(KVM_REQ_LOAD_CR3, vcpu);
+ }
+
+ kvm->arch.spp_active = true;
+ return 0;
+}
+EXPORT_SYMBOL_GPL(vmx_spp_init);
+
+int kvm_spp_get_permission(struct kvm *kvm, u64 gfn, u32 npages,
+ u32 *access_map)
+{
+ u32 *access;
+ struct kvm_memory_slot *slot;
+ int i;
+
+ if (!kvm->arch.spp_active)
+ return -ENODEV;
+
+ for (i = 0; i < npages; i++, gfn++) {
+ slot = gfn_to_memslot(kvm, gfn);
+ if (!slot)
+ return -EFAULT;
+ access = gfn_to_subpage_wp_info(slot, gfn);
+ if (!access)
+ return -EFAULT;
+ access_map[i] = *access;
+ }
+
+ return i;
+}
+EXPORT_SYMBOL_GPL(kvm_spp_get_permission);
+
+static void kvm_spp_zap_pte(struct kvm *kvm, u64 *spte, int level)
+{
+ u64 pte;
+
+ pte = *spte;
+ if (is_shadow_present_pte(pte) && is_last_spte(pte, level)) {
+ drop_spte(kvm, spte);
+ if (is_large_pte(pte))
+ --kvm->stat.lpages;
+ }
+}
+
+bool kvm_spp_flush_rmap(struct kvm *kvm, u64 gfn_min, u64 gfn_max)
+{
+ u64 *sptep;
+ struct rmap_iterator iter;
+ struct kvm_rmap_head *rmap_head;
+ int level;
+ struct kvm_memory_slot *slot;
+ bool flush = false;
+
+ slot = gfn_to_memslot(kvm, gfn_min);
+ if (!slot)
+ return false;
+
+ for (; gfn_min <= gfn_max; gfn_min++) {
+ for (level = PT_PAGE_TABLE_LEVEL;
+ level <= PT_DIRECTORY_LEVEL; level++) {
+ rmap_head = __gfn_to_rmap(gfn_min, level, slot);
+ for_each_rmap_spte(rmap_head, &iter, sptep) {
+ pte_list_remove(rmap_head, sptep);
+ flush = true;
+ }
+ }
+ }
+
+ return flush;
+}
+
+int kvm_spp_set_permission(struct kvm *kvm, u64 gfn, u32 npages,
+ u32 *access_map)
+{
+ gfn_t old_gfn = gfn;
+ u32 *access;
+ struct kvm_memory_slot *slot;
+ struct kvm_shadow_walk_iterator iterator;
+ struct kvm_vcpu *vcpu;
+ gfn_t gfn_max;
+ int i, count, level;
+ bool flush = false;
+
+ if (!kvm->arch.spp_active)
+ return -ENODEV;
+
+ vcpu = kvm_get_vcpu(kvm, 0);
+ if (!VALID_PAGE(vcpu->kvm->arch.sppt_root))
+ return -EFAULT;
+
+ for (i = 0; i < npages; i++, gfn++) {
+ slot = gfn_to_memslot(kvm, gfn);
+ if (!slot)
+ return -EFAULT;
+
+ access = gfn_to_subpage_wp_info(slot, gfn);
+ if (!access)
+ return -EFAULT;
+ *access = access_map[i];
+ }
+
+ gfn = old_gfn;
+ gfn_max = gfn + npages - 1;
+ vcpu = kvm_get_vcpu(kvm, 0);
+
+ if (!vcpu || (vcpu && !VALID_PAGE(vcpu->arch.mmu->root_hpa)))
+ goto out;
+
+ flush = kvm_spp_flush_rmap(kvm, gfn, gfn_max);
+
+ for (i = 0; gfn <= gfn_max; i++, gfn++) {
+ for_each_shadow_entry(vcpu, (u64)gfn << PAGE_SHIFT, iterator) {
+ if (!is_shadow_present_pte(*iterator.sptep))
+ break;
+
+ if (iterator.level == PT_PAGE_TABLE_LEVEL) {
+ if (kvm_spp_mark_protection(kvm,
+ gfn,
+ access_map[i]) < 0)
+ return -EFAULT;
+ break;
+ } else if (is_large_pte(*iterator.sptep)) {
+ level = iterator.level;
+ if (access_map[i] == FULL_SPP_ACCESS)
+ break;
+ count = kvm_spp_level_pages(gfn,
+ gfn_max,
+ level);
+ kvm_spp_zap_pte(kvm, iterator.sptep, level);
+ flush = true;
+ if (count >= npages)
+ goto out;
+ gfn += count - 1;
+ }
+ }
+ }
+out:
+ if (flush)
+ kvm_flush_remote_tlbs(kvm);
+ return npages;
+}
+
+int kvm_spp_mark_protection(struct kvm *kvm, u64 gfn, u32 access)
+{
+ struct kvm_memory_slot *slot;
+ struct kvm_rmap_head *rmap_head;
+ int ret;
+
+ if (!kvm->arch.spp_active)
+ return -ENODEV;
+
+ slot = gfn_to_memslot(kvm, gfn);
+ if (!slot)
+ return -EFAULT;
+
+ /*
+ * check whether the target 4KB page exists in EPT leaf
+ * entry.If it's there, just flag SPP bit of the entry,
+ * defer the setup to SPPT miss induced vm-exit 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 != FULL_SPP_ACCESS) {
+ ret = kvm_spp_open_write_protect(kvm, slot, gfn);
+ if (ret)
+ return ret;
+ } else {
+ ret = kvm_spp_clear_write_protect(kvm, slot, gfn);
+ if (ret)
+ return ret;
+ }
+ }
+
+ return 0;
+}
+
+void kvm_spp_free_memslot(struct kvm_memory_slot *free,
+ struct kvm_memory_slot *dont)
+{
+ if (!dont || free->arch.subpage_wp_info !=
+ dont->arch.subpage_wp_info) {
+ kvfree(free->arch.subpage_wp_info);
+ free->arch.subpage_wp_info = NULL;
+ }
+}
+
inline u64 construct_spptp(unsigned long root_hpa)
{
return root_hpa & PAGE_MASK;
diff --git a/arch/x86/kvm/mmu/spp.h b/arch/x86/kvm/mmu/spp.h
index 25a23a4277eb..a636d09f6db0 100644
--- a/arch/x86/kvm/mmu/spp.h
+++ b/arch/x86/kvm/mmu/spp.h
@@ -2,9 +2,21 @@
#ifndef __KVM_X86_VMX_SPP_H
#define __KVM_X86_VMX_SPP_H

+#define FULL_SPP_ACCESS ((u32)((1ULL << 32) - 1))
+
+int kvm_spp_get_permission(struct kvm *kvm, u64 gfn, u32 npages,
+ u32 *access_map);
+int kvm_spp_set_permission(struct kvm *kvm, u64 gfn, u32 npages,
+ u32 *access_map);
+int kvm_spp_mark_protection(struct kvm *kvm, u64 gfn, u32 access);
bool is_spp_spte(struct kvm_mmu_page *sp);
inline u64 construct_spptp(unsigned long root_hpa);
int kvm_spp_setup_structure(struct kvm_vcpu *vcpu,
u32 access_map, gfn_t gfn);
+int vmx_spp_flush_sppt(struct kvm *kvm, u64 gfn_base, u32 npages);
+void kvm_spp_free_memslot(struct kvm_memory_slot *free,
+ struct kvm_memory_slot *dont);
+int vmx_spp_init(struct kvm *kvm);
+u32 *gfn_to_subpage_wp_info(struct kvm_memory_slot *slot, gfn_t gfn);

#endif /* __KVM_X86_VMX_SPP_H */
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index f0a16b4adbbd..eabd55ec5af7 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -102,6 +102,14 @@ struct kvm_userspace_memory_region {
__u64 userspace_addr; /* start of the userspace allocated memory */
};

+/* for KVM_SUBPAGES_GET_ACCESS and KVM_SUBPAGES_SET_ACCESS */
+struct kvm_subpage {
+ __u64 gfn_base; /* the first page gfn of the contiguous pages */
+ __u32 npages; /* number of 4K pages */
+ __u32 flags; /* reserved to 0 now */
+ __u32 access_map[0]; /* start place of bitmap array */
+};
+
/*
* 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
--
2.17.2