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// 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>
#include <asm/vmx.h>
static bool __read_mostly enable_mmio_caching = true;
module_param_named(mmio_caching, enable_mmio_caching, bool, 0444);
u64 __read_mostly shadow_host_writable_mask;
u64 __read_mostly shadow_mmu_writable_mask;
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_mask;
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);
mask = (gen << MMIO_SPTE_GEN_LOW_SHIFT) & MMIO_SPTE_GEN_LOW_MASK;
mask |= (gen << MMIO_SPTE_GEN_HIGH_SHIFT) & 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 spte = generation_mmio_spte_mask(gen);
u64 gpa = gfn << PAGE_SHIFT;
WARN_ON_ONCE(!shadow_mmio_value);
access &= shadow_mmio_access_mask;
spte |= shadow_mmio_value | access;
spte |= gpa | shadow_nonpresent_or_rsvd_mask;
spte |= (gpa & shadow_nonpresent_or_rsvd_mask)
<< SHADOW_NONPRESENT_OR_RSVD_MASK_LEN;
return spte;
}
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 = SPTE_MMU_PRESENT_MASK;
int ret = 0;
if (ad_disabled)
spte |= SPTE_TDP_AD_DISABLED_MASK;
else if (kvm_vcpu_ad_need_write_protect(vcpu))
spte |= SPTE_TDP_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 |= static_call(kvm_x86_get_mt_mask)(vcpu, gfn,
kvm_is_mmio_pfn(pfn));
if (host_writable)
spte |= shadow_host_writable_mask;
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 | shadow_mmu_writable_mask;
/*
* Optimization: for pte sync, if spte was writable the hash
* lookup is unnecessary (and expensive). Write protection
* is responsibility of kvm_mmu_get_page / kvm_mmu_sync_roots.
* Same reasoning can be applied to dirty page accounting.
*/
if (!can_unsync && is_writable_pte(old_spte))
goto out;
/*
* Unsync shadow pages that are reachable by the new, writable
* SPTE. Write-protect the SPTE if the page can't be unsync'd,
* e.g. it's write-tracked (upper-level SPs) or has one or more
* shadow pages and unsync'ing pages is not allowed.
*/
if (mmu_try_to_unsync_pages(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 | shadow_mmu_writable_mask);
}
}
if (pte_access & ACC_WRITE_MASK)
spte |= spte_shadow_dirty_mask(spte);
if (speculative)
spte = mark_spte_for_access_track(spte);
out:
WARN_ONCE(is_rsvd_spte(&vcpu->arch.mmu->shadow_zero_check, spte, level),
"spte = 0x%llx, level = %d, rsvd bits = 0x%llx", spte, level,
get_rsvd_bits(&vcpu->arch.mmu->shadow_zero_check, spte, level));
*new_spte = spte;
return ret;
}
u64 make_nonleaf_spte(u64 *child_pt, bool ad_disabled)
{
u64 spte = SPTE_MMU_PRESENT_MASK;
spte |= __pa(child_pt) | shadow_present_mask | PT_WRITABLE_MASK |
shadow_user_mask | shadow_x_mask | shadow_me_mask;
if (ad_disabled)
spte |= SPTE_TDP_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 &= ~shadow_host_writable_mask;
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 mmio_mask, u64 access_mask)
{
BUG_ON((u64)(unsigned)access_mask != access_mask);
WARN_ON(mmio_value & shadow_nonpresent_or_rsvd_lower_gfn_mask);
if (!enable_mmio_caching)
mmio_value = 0;
/*
* Disable MMIO caching if the MMIO value collides with the bits that
* are used to hold the relocated GFN when the L1TF mitigation is
* enabled. This should never fire as there is no known hardware that
* can trigger this condition, e.g. SME/SEV CPUs that require a custom
* MMIO value are not susceptible to L1TF.
*/
if (WARN_ON(mmio_value & (shadow_nonpresent_or_rsvd_mask <<
SHADOW_NONPRESENT_OR_RSVD_MASK_LEN)))
mmio_value = 0;
/*
* The masked MMIO value must obviously match itself and a removed SPTE
* must not get a false positive. Removed SPTEs and MMIO SPTEs should
* never collide as MMIO must set some RWX bits, and removed SPTEs must
* not set any RWX bits.
*/
if (WARN_ON((mmio_value & mmio_mask) != mmio_value) ||
WARN_ON(mmio_value && (REMOVED_SPTE & mmio_mask) == mmio_value))
mmio_value = 0;
shadow_mmio_value = mmio_value;
shadow_mmio_mask = mmio_mask;
shadow_mmio_access_mask = access_mask;
}
EXPORT_SYMBOL_GPL(kvm_mmu_set_mmio_spte_mask);
void kvm_mmu_set_ept_masks(bool has_ad_bits, bool has_exec_only)
{
shadow_user_mask = VMX_EPT_READABLE_MASK;
shadow_accessed_mask = has_ad_bits ? VMX_EPT_ACCESS_BIT : 0ull;
shadow_dirty_mask = has_ad_bits ? VMX_EPT_DIRTY_BIT : 0ull;
shadow_nx_mask = 0ull;
shadow_x_mask = VMX_EPT_EXECUTABLE_MASK;
shadow_present_mask = has_exec_only ? 0ull : VMX_EPT_READABLE_MASK;
shadow_acc_track_mask = VMX_EPT_RWX_MASK;
shadow_me_mask = 0ull;
shadow_host_writable_mask = EPT_SPTE_HOST_WRITABLE;
shadow_mmu_writable_mask = EPT_SPTE_MMU_WRITABLE;
/*
* EPT Misconfigurations are generated if the value of bits 2:0
* of an EPT paging-structure entry is 110b (write/execute).
*/
kvm_mmu_set_mmio_spte_mask(VMX_EPT_MISCONFIG_WX_VALUE,
VMX_EPT_RWX_MASK, 0);
}
EXPORT_SYMBOL_GPL(kvm_mmu_set_ept_masks);
void kvm_mmu_reset_all_pte_masks(void)
{
u8 low_phys_bits;
u64 mask;
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);
shadow_user_mask = PT_USER_MASK;
shadow_accessed_mask = PT_ACCESSED_MASK;
shadow_dirty_mask = PT_DIRTY_MASK;
shadow_nx_mask = PT64_NX_MASK;
shadow_x_mask = 0;
shadow_present_mask = PT_PRESENT_MASK;
shadow_acc_track_mask = 0;
shadow_me_mask = sme_me_mask;
shadow_host_writable_mask = DEFAULT_SPTE_HOST_WRITEABLE;
shadow_mmu_writable_mask = DEFAULT_SPTE_MMU_WRITEABLE;
/*
* Set a reserved PA bit in MMIO SPTEs to generate page faults with
* PFEC.RSVD=1 on MMIO accesses. 64-bit PTEs (PAE, x86-64, and EPT
* paging) support a maximum of 52 bits of PA, i.e. if the CPU supports
* 52-bit physical addresses then there are no reserved PA bits in the
* PTEs and so the reserved PA approach must be disabled.
*/
if (shadow_phys_bits < 52)
mask = BIT_ULL(51) | PT_PRESENT_MASK;
else
mask = 0;
kvm_mmu_set_mmio_spte_mask(mask, mask, ACC_WRITE_MASK | ACC_USER_MASK);
}