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 | 19 +--- arch/x86/kvm/mmu/mmu_internal.h | 15 +++ arch/x86/kvm/mmu/tdp_iter.c | 163 ++++++++++++++++++++++++++++++++ arch/x86/kvm/mmu/tdp_iter.h | 53 +++++++++++ 5 files changed, 237 insertions(+), 16 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 4a3081e9f4b5d..cf6a9947955f7 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 kvm-amd-y += svm/svm.o svm/vmenter.o svm/pmu.o svm/nested.o svm/avic.o svm/sev.o diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 81240b558d67f..b48b00c8cde65 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -134,15 +134,6 @@ module_param(dbg, bool, 0644); #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) \ @@ -192,8 +183,6 @@ 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 @@ -346,7 +335,7 @@ 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) +bool is_mmio_spte(u64 spte) { return (spte & SPTE_SPECIAL_MASK) == SPTE_MMIO_MASK; } @@ -623,7 +612,7 @@ static int is_nx(struct kvm_vcpu *vcpu) return vcpu->arch.efer & EFER_NX; } -static int is_shadow_present_pte(u64 pte) +int is_shadow_present_pte(u64 pte) { return (pte != 0) && !is_mmio_spte(pte); } @@ -633,7 +622,7 @@ static int is_large_pte(u64 pte) return pte & PT_PAGE_SIZE_MASK; } -static int is_last_spte(u64 pte, int level) +int is_last_spte(u64 pte, int level) { if (level == PG_LEVEL_4K) return 1; @@ -647,7 +636,7 @@ 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) +kvm_pfn_t spte_to_pfn(u64 pte) { return (pte & PT64_BASE_ADDR_MASK) >> PAGE_SHIFT; } diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h index 3acf3b8eb469d..65bb110847858 100644 --- a/arch/x86/kvm/mmu/mmu_internal.h +++ b/arch/x86/kvm/mmu/mmu_internal.h @@ -60,4 +60,19 @@ 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) + +/* Functions for interpreting SPTEs */ +kvm_pfn_t spte_to_pfn(u64 pte); +bool is_mmio_spte(u64 spte); +int is_shadow_present_pte(u64 pte); +int is_last_spte(u64 pte, int level); + #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..ee90d62d2a9b1 --- /dev/null +++ b/arch/x86/kvm/mmu/tdp_iter.c @@ -0,0 +1,163 @@ +/* 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); +} + +/* + * 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, + 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->level = root_level; + iter->pt_path[iter->level - 1] = root_pt; + + iter->gfn = iter->goal_gfn - + (iter->goal_gfn % KVM_PAGES_PER_HPAGE(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) +{ + u64 *pt; + /* There's no child entry if this entry isn't present */ + if (!is_shadow_present_pte(spte)) + return NULL; + + /* There is no child page table if this is a leaf entry. */ + if (is_last_spte(spte, level)) + return NULL; + + pt = (u64 *)__va(spte_to_pfn(spte) << PAGE_SHIFT); + return pt; +} + +/* + * 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 == PG_LEVEL_4K) + 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 = iter->goal_gfn - + (iter->goal_gfn % KVM_PAGES_PER_HPAGE(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; + + 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 = iter->gfn - (iter->gfn % KVM_PAGES_PER_HPAGE(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) +{ + bool done; + + done = try_step_down(iter); + if (done) + return; + + done = try_step_side(iter); + while (!done) { + if (!try_step_up(iter)) { + iter->valid = false; + break; + } + done = try_step_side(iter); + } +} diff --git a/arch/x86/kvm/mmu/tdp_iter.h b/arch/x86/kvm/mmu/tdp_iter.h new file mode 100644 index 0000000000000..b102109778eac --- /dev/null +++ b/arch/x86/kvm/mmu/tdp_iter.h @@ -0,0 +1,53 @@ +/* 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 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, 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, + gfn_t goal_gfn); +void tdp_iter_next(struct tdp_iter *iter); + +#endif /* __KVM_X86_MMU_TDP_ITER_H */ -- 2.28.0.709.gb0816b6eb0-goog
