1 files changed, 318 insertions, 0 deletions
diff --git a/arch/x86/kvm/mmu/spte.c b/arch/x86/kvm/mmu/spte.c
new file mode 100644
index 000000000000..d9c5665a55e9
--- /dev/null
+++ b/arch/x86/kvm/mmu/spte.c
@@ -0,0 +1,318 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Kernel-based Virtual Machine driver for Linux
+ *
+ * Macros and functions to access KVM PTEs (also known as SPTEs)
+ *
+ * Copyright (C) 2006 Qumranet, Inc.
+ * Copyright 2020 Red Hat, Inc. and/or its affiliates.
+ */
+
+
+#include <linux/kvm_host.h>
+#include "mmu.h"
+#include "mmu_internal.h"
+#include "x86.h"
+#include "spte.h"
+
+#include <asm/e820/api.h>
+
+u64 __read_mostly shadow_nx_mask;
+u64 __read_mostly shadow_x_mask; /* mutual exclusive with nx_mask */
+u64 __read_mostly shadow_user_mask;
+u64 __read_mostly shadow_accessed_mask;
+u64 __read_mostly shadow_dirty_mask;
+u64 __read_mostly shadow_mmio_value;
+u64 __read_mostly shadow_mmio_access_mask;
+u64 __read_mostly shadow_present_mask;
+u64 __read_mostly shadow_me_mask;
+u64 __read_mostly shadow_acc_track_mask;
+
+u64 __read_mostly shadow_nonpresent_or_rsvd_mask;
+u64 __read_mostly shadow_nonpresent_or_rsvd_lower_gfn_mask;
+
+u8 __read_mostly shadow_phys_bits;
+
+static u64 generation_mmio_spte_mask(u64 gen)
+{
+	u64 mask;
+
+	WARN_ON(gen & ~MMIO_SPTE_GEN_MASK);
+	BUILD_BUG_ON((MMIO_SPTE_GEN_HIGH_MASK | MMIO_SPTE_GEN_LOW_MASK) & SPTE_SPECIAL_MASK);
+
+	mask = (gen << MMIO_SPTE_GEN_LOW_START) & MMIO_SPTE_GEN_LOW_MASK;
+	mask |= (gen << MMIO_SPTE_GEN_HIGH_START) & MMIO_SPTE_GEN_HIGH_MASK;
+	return mask;
+}
+
+u64 make_mmio_spte(struct kvm_vcpu *vcpu, u64 gfn, unsigned int access)
+{
+	u64 gen = kvm_vcpu_memslots(vcpu)->generation & MMIO_SPTE_GEN_MASK;
+	u64 mask = generation_mmio_spte_mask(gen);
+	u64 gpa = gfn << PAGE_SHIFT;
+
+	access &= shadow_mmio_access_mask;
+	mask |= shadow_mmio_value | access;
+	mask |= gpa | shadow_nonpresent_or_rsvd_mask;
+	mask |= (gpa & shadow_nonpresent_or_rsvd_mask)
+		<< shadow_nonpresent_or_rsvd_mask_len;
+
+	return mask;
+}
+
+static bool kvm_is_mmio_pfn(kvm_pfn_t pfn)
+{
+	if (pfn_valid(pfn))
+		return !is_zero_pfn(pfn) && PageReserved(pfn_to_page(pfn)) &&
+			/*
+			 * Some reserved pages, such as those from NVDIMM
+			 * DAX devices, are not for MMIO, and can be mapped
+			 * with cached memory type for better performance.
+			 * However, the above check misconceives those pages
+			 * as MMIO, and results in KVM mapping them with UC
+			 * memory type, which would hurt the performance.
+			 * Therefore, we check the host memory type in addition
+			 * and only treat UC/UC-/WC pages as MMIO.
+			 */
+			(!pat_enabled() || pat_pfn_immune_to_uc_mtrr(pfn));
+
+	return !e820__mapped_raw_any(pfn_to_hpa(pfn),
+				     pfn_to_hpa(pfn + 1) - 1,
+				     E820_TYPE_RAM);
+}
+
+int make_spte(struct kvm_vcpu *vcpu, unsigned int pte_access, int level,
+		     gfn_t gfn, kvm_pfn_t pfn, u64 old_spte, bool speculative,
+		     bool can_unsync, bool host_writable, bool ad_disabled,
+		     u64 *new_spte)
+{
+	u64 spte = 0;
+	int ret = 0;
+
+	if (ad_disabled)
+		spte |= SPTE_AD_DISABLED_MASK;
+	else if (kvm_vcpu_ad_need_write_protect(vcpu))
+		spte |= SPTE_AD_WRPROT_ONLY_MASK;
+
+	/*
+	 * For the EPT case, shadow_present_mask is 0 if hardware
+	 * supports exec-only page table entries.  In that case,
+	 * ACC_USER_MASK and shadow_user_mask are used to represent
+	 * read access.  See FNAME(gpte_access) in paging_tmpl.h.
+	 */
+	spte |= shadow_present_mask;
+	if (!speculative)
+		spte |= spte_shadow_accessed_mask(spte);
+
+	if (level > PG_LEVEL_4K && (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
+		spte |= shadow_nx_mask;
+
+	if (pte_access & ACC_USER_MASK)
+		spte |= shadow_user_mask;
+
+	if (level > PG_LEVEL_4K)
+		spte |= PT_PAGE_SIZE_MASK;
+	if (tdp_enabled)
+		spte |= kvm_x86_ops.get_mt_mask(vcpu, gfn,
+			kvm_is_mmio_pfn(pfn));
+
+	if (host_writable)
+		spte |= SPTE_HOST_WRITEABLE;
+	else
+		pte_access &= ~ACC_WRITE_MASK;
+
+	if (!kvm_is_mmio_pfn(pfn))
+		spte |= shadow_me_mask;
+
+	spte |= (u64)pfn << PAGE_SHIFT;
+
+	if (pte_access & ACC_WRITE_MASK) {
+		spte |= PT_WRITABLE_MASK | SPTE_MMU_WRITEABLE;
+
+		/*
+		 * Optimization: for pte sync, if spte was writable the hash
+		 * lookup is unnecessary (and expensive). Write protection
+		 * is responsibility of mmu_get_page / kvm_sync_page.
+		 * Same reasoning can be applied to dirty page accounting.
+		 */
+		if (!can_unsync && is_writable_pte(old_spte))
+			goto out;
+
+		if (mmu_need_write_protect(vcpu, gfn, can_unsync)) {
+			pgprintk("%s: found shadow page for %llx, marking ro\n",
+				 __func__, gfn);
+			ret |= SET_SPTE_WRITE_PROTECTED_PT;
+			pte_access &= ~ACC_WRITE_MASK;
+			spte &= ~(PT_WRITABLE_MASK | SPTE_MMU_WRITEABLE);
+		}
+	}
+
+	if (pte_access & ACC_WRITE_MASK)
+		spte |= spte_shadow_dirty_mask(spte);
+
+	if (speculative)
+		spte = mark_spte_for_access_track(spte);
+
+out:
+	*new_spte = spte;
+	return ret;
+}
+
+u64 make_nonleaf_spte(u64 *child_pt, bool ad_disabled)
+{
+	u64 spte;
+
+	spte = __pa(child_pt) | shadow_present_mask | PT_WRITABLE_MASK |
+	       shadow_user_mask | shadow_x_mask | shadow_me_mask;
+
+	if (ad_disabled)
+		spte |= SPTE_AD_DISABLED_MASK;
+	else
+		spte |= shadow_accessed_mask;
+
+	return spte;
+}
+
+u64 kvm_mmu_changed_pte_notifier_make_spte(u64 old_spte, kvm_pfn_t new_pfn)
+{
+	u64 new_spte;
+
+	new_spte = old_spte & ~PT64_BASE_ADDR_MASK;
+	new_spte |= (u64)new_pfn << PAGE_SHIFT;
+
+	new_spte &= ~PT_WRITABLE_MASK;
+	new_spte &= ~SPTE_HOST_WRITEABLE;
+
+	new_spte = mark_spte_for_access_track(new_spte);
+
+	return new_spte;
+}
+
+static u8 kvm_get_shadow_phys_bits(void)
+{
+	/*
+	 * boot_cpu_data.x86_phys_bits is reduced when MKTME or SME are detected
+	 * in CPU detection code, but the processor treats those reduced bits as
+	 * 'keyID' thus they are not reserved bits. Therefore KVM needs to look at
+	 * the physical address bits reported by CPUID.
+	 */
+	if (likely(boot_cpu_data.extended_cpuid_level >= 0x80000008))
+		return cpuid_eax(0x80000008) & 0xff;
+
+	/*
+	 * Quite weird to have VMX or SVM but not MAXPHYADDR; probably a VM with
+	 * custom CPUID.  Proceed with whatever the kernel found since these features
+	 * aren't virtualizable (SME/SEV also require CPUIDs higher than 0x80000008).
+	 */
+	return boot_cpu_data.x86_phys_bits;
+}
+
+u64 mark_spte_for_access_track(u64 spte)
+{
+	if (spte_ad_enabled(spte))
+		return spte & ~shadow_accessed_mask;
+
+	if (is_access_track_spte(spte))
+		return spte;
+
+	/*
+	 * Making an Access Tracking PTE will result in removal of write access
+	 * from the PTE. So, verify that we will be able to restore the write
+	 * access in the fast page fault path later on.
+	 */
+	WARN_ONCE((spte & PT_WRITABLE_MASK) &&
+		  !spte_can_locklessly_be_made_writable(spte),
+		  "kvm: Writable SPTE is not locklessly dirty-trackable\n");
+
+	WARN_ONCE(spte & (shadow_acc_track_saved_bits_mask <<
+			  shadow_acc_track_saved_bits_shift),
+		  "kvm: Access Tracking saved bit locations are not zero\n");
+
+	spte |= (spte & shadow_acc_track_saved_bits_mask) <<
+		shadow_acc_track_saved_bits_shift;
+	spte &= ~shadow_acc_track_mask;
+
+	return spte;
+}
+
+void kvm_mmu_set_mmio_spte_mask(u64 mmio_value, u64 access_mask)
+{
+	BUG_ON((u64)(unsigned)access_mask != access_mask);
+	WARN_ON(mmio_value & (shadow_nonpresent_or_rsvd_mask << shadow_nonpresent_or_rsvd_mask_len));
+	WARN_ON(mmio_value & shadow_nonpresent_or_rsvd_lower_gfn_mask);
+	shadow_mmio_value = mmio_value | SPTE_MMIO_MASK;
+	shadow_mmio_access_mask = access_mask;
+}
+EXPORT_SYMBOL_GPL(kvm_mmu_set_mmio_spte_mask);
+
+/*
+ * Sets the shadow PTE masks used by the MMU.
+ *
+ * Assumptions:
+ *  - Setting either @accessed_mask or @dirty_mask requires setting both
+ *  - At least one of @accessed_mask or @acc_track_mask must be set
+ */
+void kvm_mmu_set_mask_ptes(u64 user_mask, u64 accessed_mask,
+		u64 dirty_mask, u64 nx_mask, u64 x_mask, u64 p_mask,
+		u64 acc_track_mask, u64 me_mask)
+{
+	BUG_ON(!dirty_mask != !accessed_mask);
+	BUG_ON(!accessed_mask && !acc_track_mask);
+	BUG_ON(acc_track_mask & SPTE_SPECIAL_MASK);
+
+	shadow_user_mask = user_mask;
+	shadow_accessed_mask = accessed_mask;
+	shadow_dirty_mask = dirty_mask;
+	shadow_nx_mask = nx_mask;
+	shadow_x_mask = x_mask;
+	shadow_present_mask = p_mask;
+	shadow_acc_track_mask = acc_track_mask;
+	shadow_me_mask = me_mask;
+}
+EXPORT_SYMBOL_GPL(kvm_mmu_set_mask_ptes);
+
+void kvm_mmu_reset_all_pte_masks(void)
+{
+	u8 low_phys_bits;
+
+	shadow_user_mask = 0;
+	shadow_accessed_mask = 0;
+	shadow_dirty_mask = 0;
+	shadow_nx_mask = 0;
+	shadow_x_mask = 0;
+	shadow_present_mask = 0;
+	shadow_acc_track_mask = 0;
+
+	shadow_phys_bits = kvm_get_shadow_phys_bits();
+
+	/*
+	 * If the CPU has 46 or less physical address bits, then set an
+	 * appropriate mask to guard against L1TF attacks. Otherwise, it is
+	 * assumed that the CPU is not vulnerable to L1TF.
+	 *
+	 * Some Intel CPUs address the L1 cache using more PA bits than are
+	 * reported by CPUID. Use the PA width of the L1 cache when possible
+	 * to achieve more effective mitigation, e.g. if system RAM overlaps
+	 * the most significant bits of legal physical address space.
+	 */
+	shadow_nonpresent_or_rsvd_mask = 0;
+	low_phys_bits = boot_cpu_data.x86_phys_bits;
+	if (boot_cpu_has_bug(X86_BUG_L1TF) &&
+	    !WARN_ON_ONCE(boot_cpu_data.x86_cache_bits >=
+			  52 - shadow_nonpresent_or_rsvd_mask_len)) {
+		low_phys_bits = boot_cpu_data.x86_cache_bits
+			- shadow_nonpresent_or_rsvd_mask_len;
+		shadow_nonpresent_or_rsvd_mask =
+			rsvd_bits(low_phys_bits, boot_cpu_data.x86_cache_bits - 1);
+	}
+
+	shadow_nonpresent_or_rsvd_lower_gfn_mask =
+		GENMASK_ULL(low_phys_bits - 1, PAGE_SHIFT);
+}