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Merge branch kvm-arm64/mmu/mapping-levels into kvmarm-master/next

Browse source 
Revamp the KVM/arm64 THP code by parsing the userspace
page tables instead of relying on an infrastructure that
is about to disappear (we are the last user).

* kvm-arm64/mmu/mapping-levels:
  KVM: Get rid of kvm_get_pfn()
  KVM: arm64: Use get_page() instead of kvm_get_pfn()
  KVM: Remove kvm_is_transparent_hugepage() and PageTransCompoundMap()
  KVM: arm64: Avoid mapping size adjustment on permission fault
  KVM: arm64: Walk userspace page tables to compute the THP mapping size
  KVM: arm64: Introduce helper to retrieve a PTE and its level

Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Marc Zyngier 2021-08-20 12:14:40 +01:00
commit 2d84f3ce5e
6 changed files with 98 additions and 63 deletions
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20
arch/arm64/include/asm/kvm_pgtable.h
View file

@ -432,6 +432,26 @@ int kvm_pgtable_stage2_flush(struct kvm_pgtable *pgt, u64 addr, u64 size);
int kvm_pgtable_walk(struct kvm_pgtable *pgt, u64 addr, u64 size,
struct kvm_pgtable_walker *walker);
/**
* kvm_pgtable_get_leaf() - Walk a page-table and retrieve the leaf entry
* with its level.
* @pgt: Page-table structure initialised by kvm_pgtable_*_init()
* or a similar initialiser.
* @addr: Input address for the start of the walk.
* @ptep: Pointer to storage for the retrieved PTE.
* @level: Pointer to storage for the level of the retrieved PTE.
*
* The offset of @addr within a page is ignored.
*
* The walker will walk the page-table entries corresponding to the input
* address specified, retrieving the leaf corresponding to this address.
* Invalid entries are treated as leaf entries.
*
* Return: 0 on success, negative error code on failure.
*/
int kvm_pgtable_get_leaf(struct kvm_pgtable *pgt, u64 addr,
kvm_pte_t *ptep, u32 *level);
/**
* kvm_pgtable_stage2_find_range() - Find a range of Intermediate Physical
* Addresses with compatible permission

39
arch/arm64/kvm/hyp/pgtable.c
View file

@ -326,6 +326,45 @@ int kvm_pgtable_walk(struct kvm_pgtable *pgt, u64 addr, u64 size,
return _kvm_pgtable_walk(&walk_data);
}
struct leaf_walk_data {
kvm_pte_t pte;
u32 level;
};
static int leaf_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
enum kvm_pgtable_walk_flags flag, void * const arg)
{
struct leaf_walk_data *data = arg;
data->pte = *ptep;
data->level = level;
return 0;
}
int kvm_pgtable_get_leaf(struct kvm_pgtable *pgt, u64 addr,
kvm_pte_t *ptep, u32 *level)
{
struct leaf_walk_data data;
struct kvm_pgtable_walker walker = {
.cb = leaf_walker,
.flags = KVM_PGTABLE_WALK_LEAF,
.arg = &data,
};
int ret;
ret = kvm_pgtable_walk(pgt, ALIGN_DOWN(addr, PAGE_SIZE),
PAGE_SIZE, &walker);
if (!ret) {
if (ptep)
*ptep = data.pte;
if (level)
*level = data.level;
}
return ret;
}
struct hyp_map_data {
u64 phys;
kvm_pte_t attr;

45
arch/arm64/kvm/mmu.c
View file

@ -433,6 +433,32 @@ int create_hyp_exec_mappings(phys_addr_t phys_addr, size_t size,
return 0;
}
static struct kvm_pgtable_mm_ops kvm_user_mm_ops = {
/* We shouldn't need any other callback to walk the PT */
.phys_to_virt = kvm_host_va,
};
static int get_user_mapping_size(struct kvm *kvm, u64 addr)
{
struct kvm_pgtable pgt = {
.pgd = (kvm_pte_t *)kvm->mm->pgd,
.ia_bits = VA_BITS,
.start_level = (KVM_PGTABLE_MAX_LEVELS -
CONFIG_PGTABLE_LEVELS),
.mm_ops = &kvm_user_mm_ops,
};
kvm_pte_t pte = 0; /* Keep GCC quiet... */
u32 level = ~0;
int ret;
ret = kvm_pgtable_get_leaf(&pgt, addr, &pte, &level);
VM_BUG_ON(ret);
VM_BUG_ON(level >= KVM_PGTABLE_MAX_LEVELS);
VM_BUG_ON(!(pte & PTE_VALID));
return BIT(ARM64_HW_PGTABLE_LEVEL_SHIFT(level));
}
static struct kvm_pgtable_mm_ops kvm_s2_mm_ops = {
.zalloc_page = stage2_memcache_zalloc_page,
.zalloc_pages_exact = kvm_host_zalloc_pages_exact,
@ -780,7 +806,7 @@ static bool fault_supports_stage2_huge_mapping(struct kvm_memory_slot *memslot,
* Returns the size of the mapping.
*/
static unsigned long
transparent_hugepage_adjust(struct kvm_memory_slot *memslot,
transparent_hugepage_adjust(struct kvm *kvm, struct kvm_memory_slot *memslot,
unsigned long hva, kvm_pfn_t *pfnp,
phys_addr_t *ipap)
{
@ -791,8 +817,8 @@ transparent_hugepage_adjust(struct kvm_memory_slot *memslot,
* sure that the HVA and IPA are sufficiently aligned and that the
* block map is contained within the memslot.
*/
if (kvm_is_transparent_hugepage(pfn) &&
fault_supports_stage2_huge_mapping(memslot, hva, PMD_SIZE)) {
if (fault_supports_stage2_huge_mapping(memslot, hva, PMD_SIZE) &&
get_user_mapping_size(kvm, hva) >= PMD_SIZE) {
/*
* The address we faulted on is backed by a transparent huge
* page. However, because we map the compound huge page and
@ -814,7 +840,7 @@ transparent_hugepage_adjust(struct kvm_memory_slot *memslot,
*ipap &= PMD_MASK;
kvm_release_pfn_clean(pfn);
pfn &= ~(PTRS_PER_PMD - 1);
kvm_get_pfn(pfn);
get_page(pfn_to_page(pfn));
*pfnp = pfn;
return PMD_SIZE;
@ -1050,9 +1076,14 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
* If we are not forced to use page mapping, check if we are
* backed by a THP and thus use block mapping if possible.
*/
if (vma_pagesize == PAGE_SIZE && !(force_pte || device))
vma_pagesize = transparent_hugepage_adjust(memslot, hva,
&pfn, &fault_ipa);
if (vma_pagesize == PAGE_SIZE && !(force_pte || device)) {
if (fault_status == FSC_PERM && fault_granule > PAGE_SIZE)
vma_pagesize = fault_granule;
else
vma_pagesize = transparent_hugepage_adjust(kvm, memslot,
hva, &pfn,
&fault_ipa);
}
if (fault_status != FSC_PERM && !device && kvm_has_mte(kvm)) {
/* Check the VMM hasn't introduced a new VM_SHARED VMA */

1
include/linux/kvm_host.h
View file

@ -824,7 +824,6 @@ void kvm_release_pfn_clean(kvm_pfn_t pfn);
void kvm_release_pfn_dirty(kvm_pfn_t pfn);
void kvm_set_pfn_dirty(kvm_pfn_t pfn);
void kvm_set_pfn_accessed(kvm_pfn_t pfn);
void kvm_get_pfn(kvm_pfn_t pfn);
void kvm_release_pfn(kvm_pfn_t pfn, bool dirty, struct gfn_to_pfn_cache *cache);
int kvm_read_guest_page(struct kvm *kvm, gfn_t gfn, void *data, int offset,

37
include/linux/page-flags.h
View file

@ -632,43 +632,6 @@ static inline int PageTransCompound(struct page *page)
return PageCompound(page);
}
/*
* PageTransCompoundMap is the same as PageTransCompound, but it also
* guarantees the primary MMU has the entire compound page mapped
* through pmd_trans_huge, which in turn guarantees the secondary MMUs
* can also map the entire compound page. This allows the secondary
* MMUs to call get_user_pages() only once for each compound page and
* to immediately map the entire compound page with a single secondary
* MMU fault. If there will be a pmd split later, the secondary MMUs
* will get an update through the MMU notifier invalidation through
* split_huge_pmd().
*
* Unlike PageTransCompound, this is safe to be called only while
* split_huge_pmd() cannot run from under us, like if protected by the
* MMU notifier, otherwise it may result in page->_mapcount check false
* positives.
*
* We have to treat page cache THP differently since every subpage of it
* would get _mapcount inc'ed once it is PMD mapped. But, it may be PTE
* mapped in the current process so comparing subpage's _mapcount to
* compound_mapcount to filter out PTE mapped case.
*/
static inline int PageTransCompoundMap(struct page *page)
{
struct page *head;
if (!PageTransCompound(page))
return 0;
if (PageAnon(page))
return atomic_read(&page->_mapcount) < 0;
head = compound_head(page);
/* File THP is PMD mapped and not PTE mapped */
return atomic_read(&page->_mapcount) ==
atomic_read(compound_mapcount_ptr(head));
}
/*
* PageTransTail returns true for both transparent huge pages
* and hugetlbfs pages, so it should only be called when it's known

19
virt/kvm/kvm_main.c
View file

@ -189,16 +189,6 @@ bool kvm_is_reserved_pfn(kvm_pfn_t pfn)
return true;
}
bool kvm_is_transparent_hugepage(kvm_pfn_t pfn)
{
struct page *page = pfn_to_page(pfn);
if (!PageTransCompoundMap(page))
return false;
return is_transparent_hugepage(compound_head(page));
}
/*
* Switches to specified vcpu, until a matching vcpu_put()
*/
@ -2225,7 +2215,7 @@ static int hva_to_pfn_remapped(struct vm_area_struct *vma,
* Get a reference here because callers of *hva_to_pfn* and
* *gfn_to_pfn* ultimately call kvm_release_pfn_clean on the
* returned pfn. This is only needed if the VMA has VM_MIXEDMAP
* set, but the kvm_get_pfn/kvm_release_pfn_clean pair will
* set, but the kvm_try_get_pfn/kvm_release_pfn_clean pair will
* simply do nothing for reserved pfns.
*
* Whoever called remap_pfn_range is also going to call e.g.
@ -2622,13 +2612,6 @@ void kvm_set_pfn_accessed(kvm_pfn_t pfn)
}
EXPORT_SYMBOL_GPL(kvm_set_pfn_accessed);
void kvm_get_pfn(kvm_pfn_t pfn)
{
if (!kvm_is_reserved_pfn(pfn))
get_page(pfn_to_page(pfn));
}
EXPORT_SYMBOL_GPL(kvm_get_pfn);
static int next_segment(unsigned long len, int offset)
{
if (len > PAGE_SIZE - offset)