On Wed, Oct 14, 2020 at 11:26:42AM -0700, Ben Gardon wrote: > The TDP iterator implements a pre-order traversal of a TDP paging > structure. This iterator will be used in future patches to create > an efficient implementation of the KVM MMU for the TDP case. > > Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell > machine. This series introduced no new failures. > > This series can be viewed in Gerrit at: > https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538 > > Signed-off-by: Ben Gardon <bgardon@xxxxxxxxxx> > --- > arch/x86/kvm/Makefile | 3 +- > arch/x86/kvm/mmu/mmu.c | 66 ------------ > arch/x86/kvm/mmu/mmu_internal.h | 66 ++++++++++++ > arch/x86/kvm/mmu/tdp_iter.c | 176 ++++++++++++++++++++++++++++++++ > arch/x86/kvm/mmu/tdp_iter.h | 56 ++++++++++ > 5 files changed, 300 insertions(+), 67 deletions(-) > create mode 100644 arch/x86/kvm/mmu/tdp_iter.c > create mode 100644 arch/x86/kvm/mmu/tdp_iter.h > > diff --git a/arch/x86/kvm/Makefile b/arch/x86/kvm/Makefile > index 7f86a14aed0e9..4525c1151bf99 100644 > --- a/arch/x86/kvm/Makefile > +++ b/arch/x86/kvm/Makefile > @@ -15,7 +15,8 @@ kvm-$(CONFIG_KVM_ASYNC_PF) += $(KVM)/async_pf.o > > kvm-y += x86.o emulate.o i8259.o irq.o lapic.o \ > i8254.o ioapic.o irq_comm.o cpuid.o pmu.o mtrr.o \ > - hyperv.o debugfs.o mmu/mmu.o mmu/page_track.o > + hyperv.o debugfs.o mmu/mmu.o mmu/page_track.o \ > + mmu/tdp_iter.o > > kvm-intel-y += vmx/vmx.o vmx/vmenter.o vmx/pmu_intel.o vmx/vmcs12.o \ > vmx/evmcs.o vmx/nested.o vmx/posted_intr.o > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > index 6c9db349600c8..6d82784ed5679 100644 > --- a/arch/x86/kvm/mmu/mmu.c > +++ b/arch/x86/kvm/mmu/mmu.c > @@ -121,28 +121,6 @@ module_param(dbg, bool, 0644); > > #define PTE_PREFETCH_NUM 8 > > -#define PT_FIRST_AVAIL_BITS_SHIFT 10 > -#define PT64_SECOND_AVAIL_BITS_SHIFT 54 > - > -/* > - * The mask used to denote special SPTEs, which can be either MMIO SPTEs or > - * Access Tracking SPTEs. > - */ > -#define SPTE_SPECIAL_MASK (3ULL << 52) > -#define SPTE_AD_ENABLED_MASK (0ULL << 52) > -#define SPTE_AD_DISABLED_MASK (1ULL << 52) > -#define SPTE_AD_WRPROT_ONLY_MASK (2ULL << 52) > -#define SPTE_MMIO_MASK (3ULL << 52) > - > -#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 PT32_LEVEL_BITS 10 > > #define PT32_LEVEL_SHIFT(level) \ > @@ -155,19 +133,6 @@ module_param(dbg, bool, 0644); > #define PT32_INDEX(address, level)\ > (((address) >> PT32_LEVEL_SHIFT(level)) & ((1 << PT32_LEVEL_BITS) - 1)) > > - > -#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 PT32_BASE_ADDR_MASK PAGE_MASK > #define PT32_DIR_BASE_ADDR_MASK \ > (PAGE_MASK & ~((1ULL << (PAGE_SHIFT + PT32_LEVEL_BITS)) - 1)) > @@ -192,8 +157,6 @@ module_param(dbg, bool, 0644); > #define SPTE_HOST_WRITEABLE (1ULL << PT_FIRST_AVAIL_BITS_SHIFT) > #define SPTE_MMU_WRITEABLE (1ULL << (PT_FIRST_AVAIL_BITS_SHIFT + 1)) > > -#define SHADOW_PT_INDEX(addr, level) PT64_INDEX(addr, level) > - > /* make pte_list_desc fit well in cache line */ > #define PTE_LIST_EXT 3 > > @@ -349,11 +312,6 @@ void kvm_mmu_set_mmio_spte_mask(u64 mmio_value, u64 access_mask) > } > EXPORT_SYMBOL_GPL(kvm_mmu_set_mmio_spte_mask); > > -static bool is_mmio_spte(u64 spte) > -{ > - return (spte & SPTE_SPECIAL_MASK) == SPTE_MMIO_MASK; > -} > - > static inline bool sp_ad_disabled(struct kvm_mmu_page *sp) > { > return sp->role.ad_disabled; > @@ -626,35 +584,11 @@ static int is_nx(struct kvm_vcpu *vcpu) > return vcpu->arch.efer & EFER_NX; > } > > -static int is_shadow_present_pte(u64 pte) > -{ > - return (pte != 0) && !is_mmio_spte(pte); > -} > - > -static int is_large_pte(u64 pte) > -{ > - return pte & PT_PAGE_SIZE_MASK; > -} > - > -static int is_last_spte(u64 pte, int level) > -{ > - if (level == PG_LEVEL_4K) > - return 1; > - if (is_large_pte(pte)) > - return 1; > - return 0; > -} > - > static bool is_executable_pte(u64 spte) > { > return (spte & (shadow_x_mask | shadow_nx_mask)) == shadow_x_mask; > } > > -static kvm_pfn_t spte_to_pfn(u64 pte) > -{ > - return (pte & PT64_BASE_ADDR_MASK) >> PAGE_SHIFT; > -} > - > static gfn_t pse36_gfn_delta(u32 gpte) > { > int shift = 32 - PT32_DIR_PSE36_SHIFT - PAGE_SHIFT; > diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h > index 3acf3b8eb469d..74ccbf001a42e 100644 > --- a/arch/x86/kvm/mmu/mmu_internal.h > +++ b/arch/x86/kvm/mmu/mmu_internal.h > @@ -2,6 +2,8 @@ > #ifndef __KVM_X86_MMU_INTERNAL_H > #define __KVM_X86_MMU_INTERNAL_H > > +#include "mmu.h" > + > #include <linux/types.h> > > #include <asm/kvm_host.h> > @@ -60,4 +62,68 @@ void kvm_mmu_gfn_allow_lpage(struct kvm_memory_slot *slot, gfn_t gfn); > bool kvm_mmu_slot_gfn_write_protect(struct kvm *kvm, > struct kvm_memory_slot *slot, u64 gfn); > > +#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) > + > +#define PT_FIRST_AVAIL_BITS_SHIFT 10 > +#define PT64_SECOND_AVAIL_BITS_SHIFT 54 > + > +/* > + * The mask used to denote special SPTEs, which can be either MMIO SPTEs or > + * Access Tracking SPTEs. > + */ > +#define SPTE_SPECIAL_MASK (3ULL << 52) > +#define SPTE_AD_ENABLED_MASK (0ULL << 52) > +#define SPTE_AD_DISABLED_MASK (1ULL << 52) > +#define SPTE_AD_WRPROT_ONLY_MASK (2ULL << 52) > +#define SPTE_MMIO_MASK (3ULL << 52) > + > +#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)) > + > +/* Functions for interpreting SPTEs */ > +static inline bool is_mmio_spte(u64 spte) > +{ > + return (spte & SPTE_SPECIAL_MASK) == SPTE_MMIO_MASK; > +} > + > +static inline int is_shadow_present_pte(u64 pte) > +{ > + return (pte != 0) && !is_mmio_spte(pte); > +} > + > +static inline int is_large_pte(u64 pte) > +{ > + return pte & PT_PAGE_SIZE_MASK; > +} > + > +static inline int is_last_spte(u64 pte, int level) > +{ > + if (level == PG_LEVEL_4K) > + return 1; > + if (is_large_pte(pte)) > + return 1; > + return 0; > +} > + > +static inline kvm_pfn_t spte_to_pfn(u64 pte) > +{ > + return (pte & PT64_BASE_ADDR_MASK) >> PAGE_SHIFT; > +} > + > #endif /* __KVM_X86_MMU_INTERNAL_H */ > diff --git a/arch/x86/kvm/mmu/tdp_iter.c b/arch/x86/kvm/mmu/tdp_iter.c > new file mode 100644 > index 0000000000000..b07e9f0c5d4aa > --- /dev/null > +++ b/arch/x86/kvm/mmu/tdp_iter.c > @@ -0,0 +1,176 @@ > +// SPDX-License-Identifier: GPL-2.0 > + > +#include "mmu_internal.h" > +#include "tdp_iter.h" > + > +/* > + * Recalculates the pointer to the SPTE for the current GFN and level and > + * reread the SPTE. > + */ > +static void tdp_iter_refresh_sptep(struct tdp_iter *iter) > +{ > + iter->sptep = iter->pt_path[iter->level - 1] + > + SHADOW_PT_INDEX(iter->gfn << PAGE_SHIFT, iter->level); > + iter->old_spte = READ_ONCE(*iter->sptep); > +} > + > +static gfn_t round_gfn_for_level(gfn_t gfn, int level) > +{ > + return gfn - (gfn % KVM_PAGES_PER_HPAGE(level)); Instead of the modulo operator, how about we use: return gfn & ~(KVM_PAGES_PER_HPAGE(level) - 1); here? :) > +} > + > +/* > + * Sets a TDP iterator to walk a pre-order traversal of the paging structure > + * rooted at root_pt, starting with the walk to translate goal_gfn. > + */ > +void tdp_iter_start(struct tdp_iter *iter, u64 *root_pt, int root_level, > + int min_level, gfn_t goal_gfn) > +{ > + WARN_ON(root_level < 1); > + WARN_ON(root_level > PT64_ROOT_MAX_LEVEL); > + > + iter->goal_gfn = goal_gfn; > + iter->root_level = root_level; > + iter->min_level = min_level; > + iter->level = root_level; > + iter->pt_path[iter->level - 1] = root_pt; > + > + iter->gfn = round_gfn_for_level(iter->goal_gfn, iter->level); > + tdp_iter_refresh_sptep(iter); > + > + iter->valid = true; > +} > + > +/* > + * Given an SPTE and its level, returns a pointer containing the host virtual > + * address of the child page table referenced by the SPTE. Returns null if > + * there is no such entry. > + */ > +u64 *spte_to_child_pt(u64 spte, int level) > +{ > + /* > + * There's no child entry if this entry isn't present or is a > + * last-level entry. > + */ > + if (!is_shadow_present_pte(spte) || is_last_spte(spte, level)) > + return NULL; > + > + return __va(spte_to_pfn(spte) << PAGE_SHIFT); > +} > + > +/* > + * Steps down one level in the paging structure towards the goal GFN. Returns > + * true if the iterator was able to step down a level, false otherwise. > + */ > +static bool try_step_down(struct tdp_iter *iter) > +{ > + u64 *child_pt; > + > + if (iter->level == iter->min_level) > + return false; > + > + /* > + * Reread the SPTE before stepping down to avoid traversing into page > + * tables that are no longer linked from this entry. > + */ > + iter->old_spte = READ_ONCE(*iter->sptep); > + > + child_pt = spte_to_child_pt(iter->old_spte, iter->level); > + if (!child_pt) > + return false; > + > + iter->level--; > + iter->pt_path[iter->level - 1] = child_pt; > + iter->gfn = round_gfn_for_level(iter->goal_gfn, iter->level); > + tdp_iter_refresh_sptep(iter); > + > + return true; > +} > + > +/* > + * Steps to the next entry in the current page table, at the current page table > + * level. The next entry could point to a page backing guest memory or another > + * page table, or it could be non-present. Returns true if the iterator was > + * able to step to the next entry in the page table, false if the iterator was > + * already at the end of the current page table. > + */ > +static bool try_step_side(struct tdp_iter *iter) > +{ > + /* > + * Check if the iterator is already at the end of the current page > + * table. > + */ > + if (!((iter->gfn + KVM_PAGES_PER_HPAGE(iter->level)) % > + KVM_PAGES_PER_HPAGE(iter->level + 1))) > + return false; > + And maybe: if (SHADOW_PT_INDEX(iter->gfn << PAGE_SHIFT, iter->level) == (PT64_ENT_PER_PAGE - 1)) here? > + iter->gfn += KVM_PAGES_PER_HPAGE(iter->level); > + iter->goal_gfn = iter->gfn; > + iter->sptep++; > + iter->old_spte = READ_ONCE(*iter->sptep); > + > + return true; > +} > + > +/* > + * Tries to traverse back up a level in the paging structure so that the walk > + * can continue from the next entry in the parent page table. Returns true on a > + * successful step up, false if already in the root page. > + */ > +static bool try_step_up(struct tdp_iter *iter) > +{ > + if (iter->level == iter->root_level) > + return false; > + > + iter->level++; > + iter->gfn = round_gfn_for_level(iter->gfn, iter->level); > + tdp_iter_refresh_sptep(iter); > + > + return true; > +} > + > +/* > + * Step to the next SPTE in a pre-order traversal of the paging structure. > + * To get to the next SPTE, the iterator either steps down towards the goal > + * GFN, if at a present, non-last-level SPTE, or over to a SPTE mapping a > + * highter GFN. > + * > + * The basic algorithm is as follows: > + * 1. If the current SPTE is a non-last-level SPTE, step down into the page > + * table it points to. > + * 2. If the iterator cannot step down, it will try to step to the next SPTE > + * in the current page of the paging structure. > + * 3. If the iterator cannot step to the next entry in the current page, it will > + * try to step up to the parent paging structure page. In this case, that > + * SPTE will have already been visited, and so the iterator must also step > + * to the side again. > + */ > +void tdp_iter_next(struct tdp_iter *iter) > +{ > + if (try_step_down(iter)) > + return; > + > + do { > + if (try_step_side(iter)) > + return; > + } while (try_step_up(iter)); > + iter->valid = false; > +} > + > +/* > + * Restart the walk over the paging structure from the root, starting from the > + * highest gfn the iterator had previously reached. Assumes that the entire > + * paging structure, except the root page, may have been completely torn down > + * and rebuilt. > + */ > +void tdp_iter_refresh_walk(struct tdp_iter *iter) > +{ > + gfn_t goal_gfn = iter->goal_gfn; > + > + if (iter->gfn > goal_gfn) > + goal_gfn = iter->gfn; > + > + tdp_iter_start(iter, iter->pt_path[iter->root_level - 1], > + iter->root_level, iter->min_level, goal_gfn); > +} > + > diff --git a/arch/x86/kvm/mmu/tdp_iter.h b/arch/x86/kvm/mmu/tdp_iter.h > new file mode 100644 > index 0000000000000..d629a53e1b73f > --- /dev/null > +++ b/arch/x86/kvm/mmu/tdp_iter.h > @@ -0,0 +1,56 @@ > +// SPDX-License-Identifier: GPL-2.0 > + > +#ifndef __KVM_X86_MMU_TDP_ITER_H > +#define __KVM_X86_MMU_TDP_ITER_H > + > +#include <linux/kvm_host.h> > + > +#include "mmu.h" > + > +/* > + * A TDP iterator performs a pre-order walk over a TDP paging structure. > + */ > +struct tdp_iter { > + /* > + * The iterator will traverse the paging structure towards the mapping > + * for this GFN. > + */ > + gfn_t goal_gfn; > + /* Pointers to the page tables traversed to reach the current SPTE */ > + u64 *pt_path[PT64_ROOT_MAX_LEVEL]; > + /* A pointer to the current SPTE */ > + u64 *sptep; > + /* The lowest GFN mapped by the current SPTE */ > + gfn_t gfn; > + /* The level of the root page given to the iterator */ > + int root_level; > + /* The lowest level the iterator should traverse to */ > + int min_level; > + /* The iterator's current level within the paging structure */ > + int level; > + /* A snapshot of the value at sptep */ > + u64 old_spte; > + /* > + * Whether the iterator has a valid state. This will be false if the > + * iterator walks off the end of the paging structure. > + */ > + bool valid; > +}; > + > +/* > + * Iterates over every SPTE mapping the GFN range [start, end) in a > + * preorder traversal. > + */ > +#define for_each_tdp_pte(iter, root, root_level, start, end) \ > + for (tdp_iter_start(&iter, root, root_level, PG_LEVEL_4K, start); \ > + iter.valid && iter.gfn < end; \ > + tdp_iter_next(&iter)) > + > +u64 *spte_to_child_pt(u64 pte, int level); > + > +void tdp_iter_start(struct tdp_iter *iter, u64 *root_pt, int root_level, > + int min_level, gfn_t goal_gfn); > +void tdp_iter_next(struct tdp_iter *iter); > +void tdp_iter_refresh_walk(struct tdp_iter *iter); > + > +#endif /* __KVM_X86_MMU_TDP_ITER_H */ > -- > 2.28.0.1011.ga647a8990f-goog > I am just suggesting to replace the modulo operations with bit-shifts... Also, it's very exciting to see such patch set. Thanks! B.R. Yu
