linux/arch/x86/kvm/mmu/spte.h
Sean Christopherson 8f366ae6d8 KVM: x86/mmu: Tweak auditing WARN for A/D bits to !PRESENT (was MMIO)
Tweak the MMU_WARN that guards against weirdness when querying A/D status
to fire on a !MMU_PRESENT SPTE, as opposed to a MMIO SPTE.  Attempting to
query A/D status on any kind of !MMU_PRESENT SPTE, MMIO or otherwise,
indicates a KVM bug.  Case in point, several now-fixed bugs were
identified by enabling this new WARN.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210225204749.1512652-22-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-03-15 04:43:52 -04:00

325 lines
11 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
#ifndef KVM_X86_MMU_SPTE_H
#define KVM_X86_MMU_SPTE_H
#include "mmu_internal.h"
/*
* A MMU present SPTE is backed by actual memory and may or may not be present
* in hardware. E.g. MMIO SPTEs are not considered present. Use bit 11, as it
* is ignored by all flavors of SPTEs and checking a low bit often generates
* better code than for a high bit, e.g. 56+. MMU present checks are pervasive
* enough that the improved code generation is noticeable in KVM's footprint.
*/
#define SPTE_MMU_PRESENT_MASK BIT_ULL(11)
/*
* TDP SPTES (more specifically, EPT SPTEs) may not have A/D bits, and may also
* be restricted to using write-protection (for L2 when CPU dirty logging, i.e.
* PML, is enabled). Use bits 52 and 53 to hold the type of A/D tracking that
* is must be employed for a given TDP SPTE.
*
* Note, the "enabled" mask must be '0', as bits 62:52 are _reserved_ for PAE
* paging, including NPT PAE. This scheme works because legacy shadow paging
* is guaranteed to have A/D bits and write-protection is forced only for
* TDP with CPU dirty logging (PML). If NPT ever gains PML-like support, it
* must be restricted to 64-bit KVM.
*/
#define SPTE_TDP_AD_SHIFT 52
#define SPTE_TDP_AD_MASK (3ULL << SPTE_TDP_AD_SHIFT)
#define SPTE_TDP_AD_ENABLED_MASK (0ULL << SPTE_TDP_AD_SHIFT)
#define SPTE_TDP_AD_DISABLED_MASK (1ULL << SPTE_TDP_AD_SHIFT)
#define SPTE_TDP_AD_WRPROT_ONLY_MASK (2ULL << SPTE_TDP_AD_SHIFT)
static_assert(SPTE_TDP_AD_ENABLED_MASK == 0);
#ifdef CONFIG_DYNAMIC_PHYSICAL_MASK
#define PT64_BASE_ADDR_MASK (physical_mask & ~(u64)(PAGE_SIZE-1))
#else
#define PT64_BASE_ADDR_MASK (((1ULL << 52) - 1) & ~(u64)(PAGE_SIZE-1))
#endif
#define PT64_LVL_ADDR_MASK(level) \
(PT64_BASE_ADDR_MASK & ~((1ULL << (PAGE_SHIFT + (((level) - 1) \
* PT64_LEVEL_BITS))) - 1))
#define PT64_LVL_OFFSET_MASK(level) \
(PT64_BASE_ADDR_MASK & ((1ULL << (PAGE_SHIFT + (((level) - 1) \
* PT64_LEVEL_BITS))) - 1))
#define PT64_PERM_MASK (PT_PRESENT_MASK | PT_WRITABLE_MASK | shadow_user_mask \
| shadow_x_mask | shadow_nx_mask | shadow_me_mask)
#define ACC_EXEC_MASK 1
#define ACC_WRITE_MASK PT_WRITABLE_MASK
#define ACC_USER_MASK PT_USER_MASK
#define ACC_ALL (ACC_EXEC_MASK | ACC_WRITE_MASK | ACC_USER_MASK)
/* The mask for the R/X bits in EPT PTEs */
#define PT64_EPT_READABLE_MASK 0x1ull
#define PT64_EPT_EXECUTABLE_MASK 0x4ull
#define PT64_LEVEL_BITS 9
#define PT64_LEVEL_SHIFT(level) \
(PAGE_SHIFT + (level - 1) * PT64_LEVEL_BITS)
#define PT64_INDEX(address, level)\
(((address) >> PT64_LEVEL_SHIFT(level)) & ((1 << PT64_LEVEL_BITS) - 1))
#define SHADOW_PT_INDEX(addr, level) PT64_INDEX(addr, level)
/* Bits 9 and 10 are ignored by all non-EPT PTEs. */
#define DEFAULT_SPTE_HOST_WRITEABLE BIT_ULL(9)
#define DEFAULT_SPTE_MMU_WRITEABLE BIT_ULL(10)
/*
* The mask/shift to use for saving the original R/X bits when marking the PTE
* as not-present for access tracking purposes. We do not save the W bit as the
* PTEs being access tracked also need to be dirty tracked, so the W bit will be
* restored only when a write is attempted to the page. This mask obviously
* must not overlap the A/D type mask.
*/
#define SHADOW_ACC_TRACK_SAVED_BITS_MASK (PT64_EPT_READABLE_MASK | \
PT64_EPT_EXECUTABLE_MASK)
#define SHADOW_ACC_TRACK_SAVED_BITS_SHIFT 54
#define SHADOW_ACC_TRACK_SAVED_MASK (SHADOW_ACC_TRACK_SAVED_BITS_MASK << \
SHADOW_ACC_TRACK_SAVED_BITS_SHIFT)
static_assert(!(SPTE_TDP_AD_MASK & SHADOW_ACC_TRACK_SAVED_MASK));
/*
* Low ignored bits are at a premium for EPT, use high ignored bits, taking care
* to not overlap the A/D type mask or the saved access bits of access-tracked
* SPTEs when A/D bits are disabled.
*/
#define EPT_SPTE_HOST_WRITABLE BIT_ULL(57)
#define EPT_SPTE_MMU_WRITABLE BIT_ULL(58)
static_assert(!(EPT_SPTE_HOST_WRITABLE & SPTE_TDP_AD_MASK));
static_assert(!(EPT_SPTE_MMU_WRITABLE & SPTE_TDP_AD_MASK));
static_assert(!(EPT_SPTE_HOST_WRITABLE & SHADOW_ACC_TRACK_SAVED_MASK));
static_assert(!(EPT_SPTE_MMU_WRITABLE & SHADOW_ACC_TRACK_SAVED_MASK));
/* Defined only to keep the above static asserts readable. */
#undef SHADOW_ACC_TRACK_SAVED_MASK
/*
* Due to limited space in PTEs, the MMIO generation is a 19 bit subset of
* the memslots generation and is derived as follows:
*
* Bits 0-7 of the MMIO generation are propagated to spte bits 3-10
* Bits 8-18 of the MMIO generation are propagated to spte bits 52-62
*
* The KVM_MEMSLOT_GEN_UPDATE_IN_PROGRESS flag is intentionally not included in
* the MMIO generation number, as doing so would require stealing a bit from
* the "real" generation number and thus effectively halve the maximum number
* of MMIO generations that can be handled before encountering a wrap (which
* requires a full MMU zap). The flag is instead explicitly queried when
* checking for MMIO spte cache hits.
*/
#define MMIO_SPTE_GEN_LOW_START 3
#define MMIO_SPTE_GEN_LOW_END 10
#define MMIO_SPTE_GEN_HIGH_START 52
#define MMIO_SPTE_GEN_HIGH_END 62
#define MMIO_SPTE_GEN_LOW_MASK GENMASK_ULL(MMIO_SPTE_GEN_LOW_END, \
MMIO_SPTE_GEN_LOW_START)
#define MMIO_SPTE_GEN_HIGH_MASK GENMASK_ULL(MMIO_SPTE_GEN_HIGH_END, \
MMIO_SPTE_GEN_HIGH_START)
static_assert(!(SPTE_MMU_PRESENT_MASK &
(MMIO_SPTE_GEN_LOW_MASK | MMIO_SPTE_GEN_HIGH_MASK)));
#define MMIO_SPTE_GEN_LOW_BITS (MMIO_SPTE_GEN_LOW_END - MMIO_SPTE_GEN_LOW_START + 1)
#define MMIO_SPTE_GEN_HIGH_BITS (MMIO_SPTE_GEN_HIGH_END - MMIO_SPTE_GEN_HIGH_START + 1)
/* remember to adjust the comment above as well if you change these */
static_assert(MMIO_SPTE_GEN_LOW_BITS == 8 && MMIO_SPTE_GEN_HIGH_BITS == 11);
#define MMIO_SPTE_GEN_LOW_SHIFT (MMIO_SPTE_GEN_LOW_START - 0)
#define MMIO_SPTE_GEN_HIGH_SHIFT (MMIO_SPTE_GEN_HIGH_START - MMIO_SPTE_GEN_LOW_BITS)
#define MMIO_SPTE_GEN_MASK GENMASK_ULL(MMIO_SPTE_GEN_LOW_BITS + MMIO_SPTE_GEN_HIGH_BITS - 1, 0)
extern u64 __read_mostly shadow_host_writable_mask;
extern u64 __read_mostly shadow_mmu_writable_mask;
extern u64 __read_mostly shadow_nx_mask;
extern u64 __read_mostly shadow_x_mask; /* mutual exclusive with nx_mask */
extern u64 __read_mostly shadow_user_mask;
extern u64 __read_mostly shadow_accessed_mask;
extern u64 __read_mostly shadow_dirty_mask;
extern u64 __read_mostly shadow_mmio_value;
extern u64 __read_mostly shadow_mmio_mask;
extern u64 __read_mostly shadow_mmio_access_mask;
extern u64 __read_mostly shadow_present_mask;
extern u64 __read_mostly shadow_me_mask;
/*
* SPTEs in MMUs without A/D bits are marked with SPTE_TDP_AD_DISABLED_MASK;
* shadow_acc_track_mask is the set of bits to be cleared in non-accessed
* pages.
*/
extern u64 __read_mostly shadow_acc_track_mask;
/*
* This mask must be set on all non-zero Non-Present or Reserved SPTEs in order
* to guard against L1TF attacks.
*/
extern u64 __read_mostly shadow_nonpresent_or_rsvd_mask;
/*
* The number of high-order 1 bits to use in the mask above.
*/
#define SHADOW_NONPRESENT_OR_RSVD_MASK_LEN 5
/*
* If a thread running without exclusive control of the MMU lock must perform a
* multi-part operation on an SPTE, it can set the SPTE to REMOVED_SPTE as a
* non-present intermediate value. Other threads which encounter this value
* should not modify the SPTE.
*
* This constant works because it is considered non-present on both AMD and
* Intel CPUs and does not create a L1TF vulnerability because the pfn section
* is zeroed out.
*
* Only used by the TDP MMU.
*/
#define REMOVED_SPTE (1ull << 59)
static inline bool is_removed_spte(u64 spte)
{
return spte == REMOVED_SPTE;
}
/*
* In some cases, we need to preserve the GFN of a non-present or reserved
* SPTE when we usurp the upper five bits of the physical address space to
* defend against L1TF, e.g. for MMIO SPTEs. To preserve the GFN, we'll
* shift bits of the GFN that overlap with shadow_nonpresent_or_rsvd_mask
* left into the reserved bits, i.e. the GFN in the SPTE will be split into
* high and low parts. This mask covers the lower bits of the GFN.
*/
extern u64 __read_mostly shadow_nonpresent_or_rsvd_lower_gfn_mask;
/*
* The number of non-reserved physical address bits irrespective of features
* that repurpose legal bits, e.g. MKTME.
*/
extern u8 __read_mostly shadow_phys_bits;
static inline bool is_mmio_spte(u64 spte)
{
return (spte & shadow_mmio_mask) == shadow_mmio_value &&
likely(shadow_mmio_value);
}
static inline bool is_shadow_present_pte(u64 pte)
{
return !!(pte & SPTE_MMU_PRESENT_MASK);
}
static inline bool sp_ad_disabled(struct kvm_mmu_page *sp)
{
return sp->role.ad_disabled;
}
static inline bool spte_ad_enabled(u64 spte)
{
MMU_WARN_ON(!is_shadow_present_pte(spte));
return (spte & SPTE_TDP_AD_MASK) != SPTE_TDP_AD_DISABLED_MASK;
}
static inline bool spte_ad_need_write_protect(u64 spte)
{
MMU_WARN_ON(!is_shadow_present_pte(spte));
/*
* This is benign for non-TDP SPTEs as SPTE_TDP_AD_ENABLED_MASK is '0',
* and non-TDP SPTEs will never set these bits. Optimize for 64-bit
* TDP and do the A/D type check unconditionally.
*/
return (spte & SPTE_TDP_AD_MASK) != SPTE_TDP_AD_ENABLED_MASK;
}
static inline u64 spte_shadow_accessed_mask(u64 spte)
{
MMU_WARN_ON(!is_shadow_present_pte(spte));
return spte_ad_enabled(spte) ? shadow_accessed_mask : 0;
}
static inline u64 spte_shadow_dirty_mask(u64 spte)
{
MMU_WARN_ON(!is_shadow_present_pte(spte));
return spte_ad_enabled(spte) ? shadow_dirty_mask : 0;
}
static inline bool is_access_track_spte(u64 spte)
{
return !spte_ad_enabled(spte) && (spte & shadow_acc_track_mask) == 0;
}
static inline bool is_large_pte(u64 pte)
{
return pte & PT_PAGE_SIZE_MASK;
}
static inline bool is_last_spte(u64 pte, int level)
{
return (level == PG_LEVEL_4K) || is_large_pte(pte);
}
static inline bool is_executable_pte(u64 spte)
{
return (spte & (shadow_x_mask | shadow_nx_mask)) == shadow_x_mask;
}
static inline kvm_pfn_t spte_to_pfn(u64 pte)
{
return (pte & PT64_BASE_ADDR_MASK) >> PAGE_SHIFT;
}
static inline bool is_accessed_spte(u64 spte)
{
u64 accessed_mask = spte_shadow_accessed_mask(spte);
return accessed_mask ? spte & accessed_mask
: !is_access_track_spte(spte);
}
static inline bool is_dirty_spte(u64 spte)
{
u64 dirty_mask = spte_shadow_dirty_mask(spte);
return dirty_mask ? spte & dirty_mask : spte & PT_WRITABLE_MASK;
}
static inline bool spte_can_locklessly_be_made_writable(u64 spte)
{
return (spte & shadow_host_writable_mask) &&
(spte & shadow_mmu_writable_mask);
}
static inline u64 get_mmio_spte_generation(u64 spte)
{
u64 gen;
gen = (spte & MMIO_SPTE_GEN_LOW_MASK) >> MMIO_SPTE_GEN_LOW_SHIFT;
gen |= (spte & MMIO_SPTE_GEN_HIGH_MASK) >> MMIO_SPTE_GEN_HIGH_SHIFT;
return gen;
}
/* Bits which may be returned by set_spte() */
#define SET_SPTE_WRITE_PROTECTED_PT BIT(0)
#define SET_SPTE_NEED_REMOTE_TLB_FLUSH BIT(1)
#define SET_SPTE_SPURIOUS BIT(2)
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 make_nonleaf_spte(u64 *child_pt, bool ad_disabled);
u64 make_mmio_spte(struct kvm_vcpu *vcpu, u64 gfn, unsigned int access);
u64 mark_spte_for_access_track(u64 spte);
u64 kvm_mmu_changed_pte_notifier_make_spte(u64 old_spte, kvm_pfn_t new_pfn);
void kvm_mmu_reset_all_pte_masks(void);
#endif