Commit c9180b72 authored by Ben Gardon's avatar Ben Gardon Committed by Paolo Bonzini

kvm: x86/mmu: Introduce tdp_iter

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/+/2538Signed-off-by: default avatarBen Gardon <bgardon@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 5a9624af
...@@ -16,7 +16,7 @@ kvm-$(CONFIG_KVM_ASYNC_PF) += $(KVM)/async_pf.o ...@@ -16,7 +16,7 @@ kvm-$(CONFIG_KVM_ASYNC_PF) += $(KVM)/async_pf.o
kvm-y += x86.o emulate.o i8259.o irq.o lapic.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 \ 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/spte.o mmu/spte.o mmu/tdp_iter.o
kvm-intel-y += vmx/vmx.o vmx/vmenter.o vmx/pmu_intel.o vmx/vmcs12.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 vmx/evmcs.o vmx/nested.o vmx/posted_intr.o
......
// SPDX-License-Identifier: GPL-2.0
#include "mmu_internal.h"
#include "tdp_iter.h"
#include "spte.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 & -KVM_PAGES_PER_HPAGE(level);
}
/*
* 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 (SHADOW_PT_INDEX(iter->gfn << PAGE_SHIFT, iter->level) ==
(PT64_ENT_PER_PAGE - 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 = 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);
}
// 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 */
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