#include <asm/kvm_page_track.h>
#include "trace.h"
+extern bool itlb_multihit_kvm_mitigation;
+
+static int __read_mostly nx_huge_pages = -1;
+
+static int set_nx_huge_pages(const char *val, const struct kernel_param *kp);
+
+static struct kernel_param_ops nx_huge_pages_ops = {
+ .set = set_nx_huge_pages,
+ .get = param_get_bool,
+};
+
+module_param_cb(nx_huge_pages, &nx_huge_pages_ops, &nx_huge_pages, 0644);
+__MODULE_PARM_TYPE(nx_huge_pages, "bool");
+
/*
* When setting this variable to true it enables Two-Dimensional-Paging
* where the hardware walks 2 page tables:
return (spte & SPTE_SPECIAL_MASK) != SPTE_AD_ENABLED_MASK;
}
+static bool is_nx_huge_page_enabled(void)
+{
+ return READ_ONCE(nx_huge_pages);
+}
+
static inline u64 spte_shadow_accessed_mask(u64 spte)
{
MMU_WARN_ON(is_mmio_spte(spte));
kvm_mmu_gfn_disallow_lpage(slot, gfn);
}
+static void account_huge_nx_page(struct kvm *kvm, struct kvm_mmu_page *sp)
+{
+ if (sp->lpage_disallowed)
+ return;
+
+ ++kvm->stat.nx_lpage_splits;
+ sp->lpage_disallowed = true;
+}
+
static void unaccount_shadowed(struct kvm *kvm, struct kvm_mmu_page *sp)
{
struct kvm_memslots *slots;
kvm_mmu_gfn_allow_lpage(slot, gfn);
}
+static void unaccount_huge_nx_page(struct kvm *kvm, struct kvm_mmu_page *sp)
+{
+ --kvm->stat.nx_lpage_splits;
+ sp->lpage_disallowed = false;
+}
+
static bool __mmu_gfn_lpage_is_disallowed(gfn_t gfn, int level,
struct kvm_memory_slot *slot)
{
kvm_reload_remote_mmus(kvm);
}
+ if (sp->lpage_disallowed)
+ unaccount_huge_nx_page(kvm, sp);
+
sp->role.invalid = 1;
return list_unstable;
}
if (!speculative)
spte |= spte_shadow_accessed_mask(spte);
+ if (level > PT_PAGE_TABLE_LEVEL && (pte_access & ACC_EXEC_MASK) &&
+ is_nx_huge_page_enabled()) {
+ pte_access &= ~ACC_EXEC_MASK;
+ }
+
if (pte_access & ACC_EXEC_MASK)
spte |= shadow_x_mask;
else
__direct_pte_prefetch(vcpu, sp, sptep);
}
+static void disallowed_hugepage_adjust(struct kvm_shadow_walk_iterator it,
+ gfn_t gfn, kvm_pfn_t *pfnp, int *levelp)
+{
+ int level = *levelp;
+ u64 spte = *it.sptep;
+
+ if (it.level == level && level > PT_PAGE_TABLE_LEVEL &&
+ is_nx_huge_page_enabled() &&
+ is_shadow_present_pte(spte) &&
+ !is_large_pte(spte)) {
+ /*
+ * A small SPTE exists for this pfn, but FNAME(fetch)
+ * and __direct_map would like to create a large PTE
+ * instead: just force them to go down another level,
+ * patching back for them into pfn the next 9 bits of
+ * the address.
+ */
+ u64 page_mask = KVM_PAGES_PER_HPAGE(level) - KVM_PAGES_PER_HPAGE(level - 1);
+ *pfnp |= gfn & page_mask;
+ (*levelp)--;
+ }
+}
+
static int __direct_map(struct kvm_vcpu *vcpu, gpa_t gpa, int write,
int map_writable, int level, kvm_pfn_t pfn,
- bool prefault)
+ bool prefault, bool lpage_disallowed)
{
struct kvm_shadow_walk_iterator it;
struct kvm_mmu_page *sp;
trace_kvm_mmu_spte_requested(gpa, level, pfn);
for_each_shadow_entry(vcpu, gpa, it) {
+ /*
+ * We cannot overwrite existing page tables with an NX
+ * large page, as the leaf could be executable.
+ */
+ disallowed_hugepage_adjust(it, gfn, &pfn, &level);
+
base_gfn = gfn & ~(KVM_PAGES_PER_HPAGE(it.level) - 1);
if (it.level == level)
break;
it.level - 1, true, ACC_ALL);
link_shadow_page(vcpu, it.sptep, sp);
+ if (lpage_disallowed)
+ account_huge_nx_page(vcpu->kvm, sp);
}
}
{
int r;
int level;
- bool force_pt_level = false;
+ bool force_pt_level;
kvm_pfn_t pfn;
unsigned long mmu_seq;
bool map_writable, write = error_code & PFERR_WRITE_MASK;
+ bool lpage_disallowed = (error_code & PFERR_FETCH_MASK) &&
+ is_nx_huge_page_enabled();
+ force_pt_level = lpage_disallowed;
level = mapping_level(vcpu, gfn, &force_pt_level);
if (likely(!force_pt_level)) {
/*
goto out_unlock;
if (likely(!force_pt_level))
transparent_hugepage_adjust(vcpu, gfn, &pfn, &level);
- r = __direct_map(vcpu, v, write, map_writable, level, pfn, prefault);
+ r = __direct_map(vcpu, v, write, map_writable, level, pfn,
+ prefault, false);
out_unlock:
spin_unlock(&vcpu->kvm->mmu_lock);
kvm_release_pfn_clean(pfn);
unsigned long mmu_seq;
int write = error_code & PFERR_WRITE_MASK;
bool map_writable;
+ bool lpage_disallowed = (error_code & PFERR_FETCH_MASK) &&
+ is_nx_huge_page_enabled();
MMU_WARN_ON(!VALID_PAGE(vcpu->arch.mmu->root_hpa));
if (r)
return r;
- force_pt_level = !check_hugepage_cache_consistency(vcpu, gfn,
- PT_DIRECTORY_LEVEL);
+ force_pt_level =
+ lpage_disallowed ||
+ !check_hugepage_cache_consistency(vcpu, gfn, PT_DIRECTORY_LEVEL);
level = mapping_level(vcpu, gfn, &force_pt_level);
if (likely(!force_pt_level)) {
if (level > PT_DIRECTORY_LEVEL &&
goto out_unlock;
if (likely(!force_pt_level))
transparent_hugepage_adjust(vcpu, gfn, &pfn, &level);
- r = __direct_map(vcpu, gpa, write, map_writable, level, pfn, prefault);
+ r = __direct_map(vcpu, gpa, write, map_writable, level, pfn,
+ prefault, lpage_disallowed);
out_unlock:
spin_unlock(&vcpu->kvm->mmu_lock);
kvm_release_pfn_clean(pfn);
kvm_mmu_set_mmio_spte_mask(mask, mask, ACC_WRITE_MASK | ACC_USER_MASK);
}
+static bool get_nx_auto_mode(void)
+{
+ /* Return true when CPU has the bug, and mitigations are ON */
+ return boot_cpu_has_bug(X86_BUG_ITLB_MULTIHIT) && !cpu_mitigations_off();
+}
+
+static void __set_nx_huge_pages(bool val)
+{
+ nx_huge_pages = itlb_multihit_kvm_mitigation = val;
+}
+
+static int set_nx_huge_pages(const char *val, const struct kernel_param *kp)
+{
+ bool old_val = nx_huge_pages;
+ bool new_val;
+
+ /* In "auto" mode deploy workaround only if CPU has the bug. */
+ if (sysfs_streq(val, "off"))
+ new_val = 0;
+ else if (sysfs_streq(val, "force"))
+ new_val = 1;
+ else if (sysfs_streq(val, "auto"))
+ new_val = get_nx_auto_mode();
+ else if (strtobool(val, &new_val) < 0)
+ return -EINVAL;
+
+ __set_nx_huge_pages(new_val);
+
+ if (new_val != old_val) {
+ struct kvm *kvm;
+ int idx;
+
+ mutex_lock(&kvm_lock);
+
+ list_for_each_entry(kvm, &vm_list, vm_list) {
+ idx = srcu_read_lock(&kvm->srcu);
+ kvm_mmu_zap_all_fast(kvm);
+ srcu_read_unlock(&kvm->srcu, idx);
+ }
+ mutex_unlock(&kvm_lock);
+ }
+
+ return 0;
+}
+
int kvm_mmu_module_init(void)
{
int ret = -ENOMEM;
+ if (nx_huge_pages == -1)
+ __set_nx_huge_pages(get_nx_auto_mode());
+
/*
* MMU roles use union aliasing which is, generally speaking, an
* undefined behavior. However, we supposedly know how compilers behave
static int FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
struct guest_walker *gw,
int write_fault, int hlevel,
- kvm_pfn_t pfn, bool map_writable, bool prefault)
+ kvm_pfn_t pfn, bool map_writable, bool prefault,
+ bool lpage_disallowed)
{
struct kvm_mmu_page *sp = NULL;
struct kvm_shadow_walk_iterator it;
unsigned direct_access, access = gw->pt_access;
int top_level, ret;
- gfn_t base_gfn;
+ gfn_t gfn, base_gfn;
direct_access = gw->pte_access;
link_shadow_page(vcpu, it.sptep, sp);
}
- base_gfn = gw->gfn;
+ /*
+ * FNAME(page_fault) might have clobbered the bottom bits of
+ * gw->gfn, restore them from the virtual address.
+ */
+ gfn = gw->gfn | ((addr & PT_LVL_OFFSET_MASK(gw->level)) >> PAGE_SHIFT);
+ base_gfn = gfn;
trace_kvm_mmu_spte_requested(addr, gw->level, pfn);
for (; shadow_walk_okay(&it); shadow_walk_next(&it)) {
clear_sp_write_flooding_count(it.sptep);
- base_gfn = gw->gfn & ~(KVM_PAGES_PER_HPAGE(it.level) - 1);
+
+ /*
+ * We cannot overwrite existing page tables with an NX
+ * large page, as the leaf could be executable.
+ */
+ disallowed_hugepage_adjust(it, gfn, &pfn, &hlevel);
+
+ base_gfn = gfn & ~(KVM_PAGES_PER_HPAGE(it.level) - 1);
if (it.level == hlevel)
break;
sp = kvm_mmu_get_page(vcpu, base_gfn, addr,
it.level - 1, true, direct_access);
link_shadow_page(vcpu, it.sptep, sp);
+ if (lpage_disallowed)
+ account_huge_nx_page(vcpu->kvm, sp);
}
}
int r;
kvm_pfn_t pfn;
int level = PT_PAGE_TABLE_LEVEL;
- bool force_pt_level = false;
unsigned long mmu_seq;
bool map_writable, is_self_change_mapping;
+ bool lpage_disallowed = (error_code & PFERR_FETCH_MASK) &&
+ is_nx_huge_page_enabled();
+ bool force_pt_level = lpage_disallowed;
pgprintk("%s: addr %lx err %x\n", __func__, addr, error_code);
if (!force_pt_level)
transparent_hugepage_adjust(vcpu, walker.gfn, &pfn, &level);
r = FNAME(fetch)(vcpu, addr, &walker, write_fault,
- level, pfn, map_writable, prefault);
+ level, pfn, map_writable, prefault, lpage_disallowed);
kvm_mmu_audit(vcpu, AUDIT_POST_PAGE_FAULT);
out_unlock:
projects / nvme.git / commitdiff