* [PATCH 3/4] KVM: ARM: Support hugetlbfs backed huge pages
2013-10-23 9:19 [GIT PULL] Second round of KVM/ARM updates for 3.13 Christoffer Dall
2013-10-23 9:19 ` [PATCH 1/4] ARM: KVM: Yield CPU when vcpu executes a WFE Christoffer Dall
2013-10-23 9:19 ` [PATCH 2/4] KVM: ARM: Update comments for kvm_handle_wfi Christoffer Dall
@ 2013-10-23 9:19 ` Christoffer Dall
2013-10-23 9:19 ` [PATCH 4/4] KVM: ARM: Transparent huge page (THP) support Christoffer Dall
3 siblings, 0 replies; 5+ messages in thread
From: Christoffer Dall @ 2013-10-23 9:19 UTC (permalink / raw)
To: linux-arm-kernel
Support huge pages in KVM/ARM and KVM/ARM64. The pud_huge checking on
the unmap path may feel a bit silly as the pud_huge check is always
defined to false, but the compiler should be smart about this.
Note: This deals only with VMAs marked as huge which are allocated by
users through hugetlbfs only. Transparent huge pages can only be
detected by looking at the underlying pages (or the page tables
themselves) and this patch so far simply maps these on a page-by-page
level in the Stage-2 page tables.
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
---
arch/arm/include/asm/kvm_mmu.h | 17 +++-
arch/arm/include/asm/pgtable-3level.h | 2 +
arch/arm/kvm/mmu.c | 169 +++++++++++++++++++++++++-------
arch/arm64/include/asm/kvm_mmu.h | 12 ++-
arch/arm64/include/asm/pgtable-hwdef.h | 2 +
5 files changed, 158 insertions(+), 44 deletions(-)
diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
index 9b28c41..77de4a4 100644
--- a/arch/arm/include/asm/kvm_mmu.h
+++ b/arch/arm/include/asm/kvm_mmu.h
@@ -62,6 +62,12 @@ phys_addr_t kvm_get_idmap_vector(void);
int kvm_mmu_init(void);
void kvm_clear_hyp_idmap(void);
+static inline void kvm_set_pmd(pmd_t *pmd, pmd_t new_pmd)
+{
+ *pmd = new_pmd;
+ flush_pmd_entry(pmd);
+}
+
static inline void kvm_set_pte(pte_t *pte, pte_t new_pte)
{
*pte = new_pte;
@@ -103,9 +109,15 @@ static inline void kvm_set_s2pte_writable(pte_t *pte)
pte_val(*pte) |= L_PTE_S2_RDWR;
}
+static inline void kvm_set_s2pmd_writable(pmd_t *pmd)
+{
+ pmd_val(*pmd) |= L_PMD_S2_RDWR;
+}
+
struct kvm;
-static inline void coherent_icache_guest_page(struct kvm *kvm, gfn_t gfn)
+static inline void coherent_icache_guest_page(struct kvm *kvm, hva_t hva,
+ unsigned long size)
{
/*
* If we are going to insert an instruction page and the icache is
@@ -120,8 +132,7 @@ static inline void coherent_icache_guest_page(struct kvm *kvm, gfn_t gfn)
* need any kind of flushing (DDI 0406C.b - Page B3-1392).
*/
if (icache_is_pipt()) {
- unsigned long hva = gfn_to_hva(kvm, gfn);
- __cpuc_coherent_user_range(hva, hva + PAGE_SIZE);
+ __cpuc_coherent_user_range(hva, hva + size);
} else if (!icache_is_vivt_asid_tagged()) {
/* any kind of VIPT cache */
__flush_icache_all();
diff --git a/arch/arm/include/asm/pgtable-3level.h b/arch/arm/include/asm/pgtable-3level.h
index 5689c18..a331d25 100644
--- a/arch/arm/include/asm/pgtable-3level.h
+++ b/arch/arm/include/asm/pgtable-3level.h
@@ -126,6 +126,8 @@
#define L_PTE_S2_RDONLY (_AT(pteval_t, 1) << 6) /* HAP[1] */
#define L_PTE_S2_RDWR (_AT(pteval_t, 3) << 6) /* HAP[2:1] */
+#define L_PMD_S2_RDWR (_AT(pmdval_t, 3) << 6) /* HAP[2:1] */
+
/*
* Hyp-mode PL2 PTE definitions for LPAE.
*/
diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index b0de86b..745d8b1 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -19,6 +19,7 @@
#include <linux/mman.h>
#include <linux/kvm_host.h>
#include <linux/io.h>
+#include <linux/hugetlb.h>
#include <trace/events/kvm.h>
#include <asm/pgalloc.h>
#include <asm/cacheflush.h>
@@ -41,6 +42,8 @@ static unsigned long hyp_idmap_start;
static unsigned long hyp_idmap_end;
static phys_addr_t hyp_idmap_vector;
+#define kvm_pmd_huge(_x) (pmd_huge(_x))
+
static void kvm_tlb_flush_vmid_ipa(struct kvm *kvm, phys_addr_t ipa)
{
/*
@@ -93,19 +96,29 @@ static bool page_empty(void *ptr)
static void clear_pud_entry(struct kvm *kvm, pud_t *pud, phys_addr_t addr)
{
- pmd_t *pmd_table = pmd_offset(pud, 0);
- pud_clear(pud);
- kvm_tlb_flush_vmid_ipa(kvm, addr);
- pmd_free(NULL, pmd_table);
+ if (pud_huge(*pud)) {
+ pud_clear(pud);
+ kvm_tlb_flush_vmid_ipa(kvm, addr);
+ } else {
+ pmd_t *pmd_table = pmd_offset(pud, 0);
+ pud_clear(pud);
+ kvm_tlb_flush_vmid_ipa(kvm, addr);
+ pmd_free(NULL, pmd_table);
+ }
put_page(virt_to_page(pud));
}
static void clear_pmd_entry(struct kvm *kvm, pmd_t *pmd, phys_addr_t addr)
{
- pte_t *pte_table = pte_offset_kernel(pmd, 0);
- pmd_clear(pmd);
- kvm_tlb_flush_vmid_ipa(kvm, addr);
- pte_free_kernel(NULL, pte_table);
+ if (kvm_pmd_huge(*pmd)) {
+ pmd_clear(pmd);
+ kvm_tlb_flush_vmid_ipa(kvm, addr);
+ } else {
+ pte_t *pte_table = pte_offset_kernel(pmd, 0);
+ pmd_clear(pmd);
+ kvm_tlb_flush_vmid_ipa(kvm, addr);
+ pte_free_kernel(NULL, pte_table);
+ }
put_page(virt_to_page(pmd));
}
@@ -136,18 +149,32 @@ static void unmap_range(struct kvm *kvm, pgd_t *pgdp,
continue;
}
+ if (pud_huge(*pud)) {
+ /*
+ * If we are dealing with a huge pud, just clear it and
+ * move on.
+ */
+ clear_pud_entry(kvm, pud, addr);
+ addr = pud_addr_end(addr, end);
+ continue;
+ }
+
pmd = pmd_offset(pud, addr);
if (pmd_none(*pmd)) {
addr = pmd_addr_end(addr, end);
continue;
}
- pte = pte_offset_kernel(pmd, addr);
- clear_pte_entry(kvm, pte, addr);
- next = addr + PAGE_SIZE;
+ if (!kvm_pmd_huge(*pmd)) {
+ pte = pte_offset_kernel(pmd, addr);
+ clear_pte_entry(kvm, pte, addr);
+ next = addr + PAGE_SIZE;
+ }
- /* If we emptied the pte, walk back up the ladder */
- if (page_empty(pte)) {
+ /*
+ * If the pmd entry is to be cleared, walk back up the ladder
+ */
+ if (kvm_pmd_huge(*pmd) || page_empty(pte)) {
clear_pmd_entry(kvm, pmd, addr);
next = pmd_addr_end(addr, end);
if (page_empty(pmd) && !page_empty(pud)) {
@@ -420,29 +447,71 @@ void kvm_free_stage2_pgd(struct kvm *kvm)
kvm->arch.pgd = NULL;
}
-
-static int stage2_set_pte(struct kvm *kvm, struct kvm_mmu_memory_cache *cache,
- phys_addr_t addr, const pte_t *new_pte, bool iomap)
+static pmd_t *stage2_get_pmd(struct kvm *kvm, struct kvm_mmu_memory_cache *cache,
+ phys_addr_t addr)
{
pgd_t *pgd;
pud_t *pud;
pmd_t *pmd;
- pte_t *pte, old_pte;
- /* Create 2nd stage page table mapping - Level 1 */
pgd = kvm->arch.pgd + pgd_index(addr);
pud = pud_offset(pgd, addr);
if (pud_none(*pud)) {
if (!cache)
- return 0; /* ignore calls from kvm_set_spte_hva */
+ return NULL;
pmd = mmu_memory_cache_alloc(cache);
pud_populate(NULL, pud, pmd);
get_page(virt_to_page(pud));
}
- pmd = pmd_offset(pud, addr);
+ return pmd_offset(pud, addr);
+}
+
+static int stage2_set_pmd_huge(struct kvm *kvm, struct kvm_mmu_memory_cache
+ *cache, phys_addr_t addr, const pmd_t *new_pmd)
+{
+ pmd_t *pmd, old_pmd;
+
+ pmd = stage2_get_pmd(kvm, cache, addr);
+ VM_BUG_ON(!pmd);
- /* Create 2nd stage page table mapping - Level 2 */
+ /*
+ * Mapping in huge pages should only happen through a fault. If a
+ * page is merged into a transparent huge page, the individual
+ * subpages of that huge page should be unmapped through MMU
+ * notifiers before we get here.
+ *
+ * Merging of CompoundPages is not supported; they should become
+ * splitting first, unmapped, merged, and mapped back in on-demand.
+ */
+ VM_BUG_ON(pmd_present(*pmd) && pmd_pfn(*pmd) != pmd_pfn(*new_pmd));
+
+ old_pmd = *pmd;
+ kvm_set_pmd(pmd, *new_pmd);
+ if (pmd_present(old_pmd))
+ kvm_tlb_flush_vmid_ipa(kvm, addr);
+ else
+ get_page(virt_to_page(pmd));
+ return 0;
+}
+
+static int stage2_set_pte(struct kvm *kvm, struct kvm_mmu_memory_cache *cache,
+ phys_addr_t addr, const pte_t *new_pte, bool iomap)
+{
+ pmd_t *pmd;
+ pte_t *pte, old_pte;
+
+ /* Create stage-2 page table mapping - Level 1 */
+ pmd = stage2_get_pmd(kvm, cache, addr);
+ if (!pmd) {
+ /*
+ * Ignore calls from kvm_set_spte_hva for unallocated
+ * address ranges.
+ */
+ return 0;
+ }
+
+ /* Create stage-2 page mappings - Level 2 */
if (pmd_none(*pmd)) {
if (!cache)
return 0; /* ignore calls from kvm_set_spte_hva */
@@ -508,15 +577,18 @@ out:
}
static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
- gfn_t gfn, struct kvm_memory_slot *memslot,
+ struct kvm_memory_slot *memslot,
unsigned long fault_status)
{
- pte_t new_pte;
- pfn_t pfn;
int ret;
- bool write_fault, writable;
+ bool write_fault, writable, hugetlb = false;
unsigned long mmu_seq;
+ gfn_t gfn = fault_ipa >> PAGE_SHIFT;
+ unsigned long hva = gfn_to_hva(vcpu->kvm, gfn);
+ struct kvm *kvm = vcpu->kvm;
struct kvm_mmu_memory_cache *memcache = &vcpu->arch.mmu_page_cache;
+ struct vm_area_struct *vma;
+ pfn_t pfn;
write_fault = kvm_is_write_fault(kvm_vcpu_get_hsr(vcpu));
if (fault_status == FSC_PERM && !write_fault) {
@@ -524,6 +596,15 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
return -EFAULT;
}
+ /* Let's check if we will get back a huge page backed by hugetlbfs */
+ down_read(¤t->mm->mmap_sem);
+ vma = find_vma_intersection(current->mm, hva, hva + 1);
+ if (is_vm_hugetlb_page(vma)) {
+ hugetlb = true;
+ gfn = (fault_ipa & PMD_MASK) >> PAGE_SHIFT;
+ }
+ up_read(¤t->mm->mmap_sem);
+
/* We need minimum second+third level pages */
ret = mmu_topup_memory_cache(memcache, 2, KVM_NR_MEM_OBJS);
if (ret)
@@ -541,26 +622,38 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
*/
smp_rmb();
- pfn = gfn_to_pfn_prot(vcpu->kvm, gfn, write_fault, &writable);
+ pfn = gfn_to_pfn_prot(kvm, gfn, write_fault, &writable);
if (is_error_pfn(pfn))
return -EFAULT;
- new_pte = pfn_pte(pfn, PAGE_S2);
- coherent_icache_guest_page(vcpu->kvm, gfn);
-
- spin_lock(&vcpu->kvm->mmu_lock);
- if (mmu_notifier_retry(vcpu->kvm, mmu_seq))
+ spin_lock(&kvm->mmu_lock);
+ if (mmu_notifier_retry(kvm, mmu_seq))
goto out_unlock;
- if (writable) {
- kvm_set_s2pte_writable(&new_pte);
- kvm_set_pfn_dirty(pfn);
+
+ if (hugetlb) {
+ pmd_t new_pmd = pfn_pmd(pfn, PAGE_S2);
+ new_pmd = pmd_mkhuge(new_pmd);
+ if (writable) {
+ kvm_set_s2pmd_writable(&new_pmd);
+ kvm_set_pfn_dirty(pfn);
+ }
+ coherent_icache_guest_page(kvm, hva & PMD_MASK, PMD_SIZE);
+ ret = stage2_set_pmd_huge(kvm, memcache, fault_ipa, &new_pmd);
+ } else {
+ pte_t new_pte = pfn_pte(pfn, PAGE_S2);
+ if (writable) {
+ kvm_set_s2pte_writable(&new_pte);
+ kvm_set_pfn_dirty(pfn);
+ }
+ coherent_icache_guest_page(kvm, hva, PAGE_SIZE);
+ ret = stage2_set_pte(kvm, memcache, fault_ipa, &new_pte, false);
}
- stage2_set_pte(vcpu->kvm, memcache, fault_ipa, &new_pte, false);
+
out_unlock:
- spin_unlock(&vcpu->kvm->mmu_lock);
+ spin_unlock(&kvm->mmu_lock);
kvm_release_pfn_clean(pfn);
- return 0;
+ return ret;
}
/**
@@ -629,7 +722,7 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu, struct kvm_run *run)
memslot = gfn_to_memslot(vcpu->kvm, gfn);
- ret = user_mem_abort(vcpu, fault_ipa, gfn, memslot, fault_status);
+ ret = user_mem_abort(vcpu, fault_ipa, memslot, fault_status);
if (ret == 0)
ret = 1;
out_unlock:
diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index efe609c..680f74e 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -91,6 +91,7 @@ int kvm_mmu_init(void);
void kvm_clear_hyp_idmap(void);
#define kvm_set_pte(ptep, pte) set_pte(ptep, pte)
+#define kvm_set_pmd(pmdp, pmd) set_pmd(pmdp, pmd)
static inline bool kvm_is_write_fault(unsigned long esr)
{
@@ -116,13 +117,18 @@ static inline void kvm_set_s2pte_writable(pte_t *pte)
pte_val(*pte) |= PTE_S2_RDWR;
}
+static inline void kvm_set_s2pmd_writable(pmd_t *pmd)
+{
+ pmd_val(*pmd) |= PMD_S2_RDWR;
+}
+
struct kvm;
-static inline void coherent_icache_guest_page(struct kvm *kvm, gfn_t gfn)
+static inline void coherent_icache_guest_page(struct kvm *kvm, hva_t hva,
+ unsigned long size)
{
if (!icache_is_aliasing()) { /* PIPT */
- unsigned long hva = gfn_to_hva(kvm, gfn);
- flush_icache_range(hva, hva + PAGE_SIZE);
+ flush_icache_range(hva, hva + size);
} else if (!icache_is_aivivt()) { /* non ASID-tagged VIVT */
/* any kind of VIPT cache */
__flush_icache_all();
diff --git a/arch/arm64/include/asm/pgtable-hwdef.h b/arch/arm64/include/asm/pgtable-hwdef.h
index d57e668..755f861 100644
--- a/arch/arm64/include/asm/pgtable-hwdef.h
+++ b/arch/arm64/include/asm/pgtable-hwdef.h
@@ -85,6 +85,8 @@
#define PTE_S2_RDONLY (_AT(pteval_t, 1) << 6) /* HAP[2:1] */
#define PTE_S2_RDWR (_AT(pteval_t, 3) << 6) /* HAP[2:1] */
+#define PMD_S2_RDWR (_AT(pmdval_t, 3) << 6) /* HAP[2:1] */
+
/*
* Memory Attribute override for Stage-2 (MemAttr[3:0])
*/
--
1.7.10.4
^ permalink raw reply related [flat|nested] 5+ messages in thread* [PATCH 4/4] KVM: ARM: Transparent huge page (THP) support
2013-10-23 9:19 [GIT PULL] Second round of KVM/ARM updates for 3.13 Christoffer Dall
` (2 preceding siblings ...)
2013-10-23 9:19 ` [PATCH 3/4] KVM: ARM: Support hugetlbfs backed huge pages Christoffer Dall
@ 2013-10-23 9:19 ` Christoffer Dall
3 siblings, 0 replies; 5+ messages in thread
From: Christoffer Dall @ 2013-10-23 9:19 UTC (permalink / raw)
To: linux-arm-kernel
Support transparent huge pages in KVM/ARM and KVM/ARM64. The
transparent_hugepage_adjust is not very pretty, but this is also how
it's solved on x86 and seems to be simply an artifact on how THPs
behave. This should eventually be shared across architectures if
possible, but that can always be changed down the road.
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
---
arch/arm/kvm/mmu.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 56 insertions(+), 2 deletions(-)
diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index 745d8b1..3719583 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -42,7 +42,7 @@ static unsigned long hyp_idmap_start;
static unsigned long hyp_idmap_end;
static phys_addr_t hyp_idmap_vector;
-#define kvm_pmd_huge(_x) (pmd_huge(_x))
+#define kvm_pmd_huge(_x) (pmd_huge(_x) || pmd_trans_huge(_x))
static void kvm_tlb_flush_vmid_ipa(struct kvm *kvm, phys_addr_t ipa)
{
@@ -576,12 +576,53 @@ out:
return ret;
}
+static bool transparent_hugepage_adjust(pfn_t *pfnp, phys_addr_t *ipap)
+{
+ pfn_t pfn = *pfnp;
+ gfn_t gfn = *ipap >> PAGE_SHIFT;
+
+ if (PageTransCompound(pfn_to_page(pfn))) {
+ unsigned long mask;
+ /*
+ * The address we faulted on is backed by a transparent huge
+ * page. However, because we map the compound huge page and
+ * not the individual tail page, we need to transfer the
+ * refcount to the head page. We have to be careful that the
+ * THP doesn't start to split while we are adjusting the
+ * refcounts.
+ *
+ * We are sure this doesn't happen, because mmu_notifier_retry
+ * was successful and we are holding the mmu_lock, so if this
+ * THP is trying to split, it will be blocked in the mmu
+ * notifier before touching any of the pages, specifically
+ * before being able to call __split_huge_page_refcount().
+ *
+ * We can therefore safely transfer the refcount from PG_tail
+ * to PG_head and switch the pfn from a tail page to the head
+ * page accordingly.
+ */
+ mask = PTRS_PER_PMD - 1;
+ VM_BUG_ON((gfn & mask) != (pfn & mask));
+ if (pfn & mask) {
+ *ipap &= PMD_MASK;
+ kvm_release_pfn_clean(pfn);
+ pfn &= ~mask;
+ kvm_get_pfn(pfn);
+ *pfnp = pfn;
+ }
+
+ return true;
+ }
+
+ return false;
+}
+
static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
struct kvm_memory_slot *memslot,
unsigned long fault_status)
{
int ret;
- bool write_fault, writable, hugetlb = false;
+ bool write_fault, writable, hugetlb = false, force_pte = false;
unsigned long mmu_seq;
gfn_t gfn = fault_ipa >> PAGE_SHIFT;
unsigned long hva = gfn_to_hva(vcpu->kvm, gfn);
@@ -602,6 +643,17 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
if (is_vm_hugetlb_page(vma)) {
hugetlb = true;
gfn = (fault_ipa & PMD_MASK) >> PAGE_SHIFT;
+ } else {
+ /*
+ * Pages belonging to VMAs not aligned to the PMD mapping
+ * granularity cannot be mapped using block descriptors even
+ * if the pages belong to a THP for the process, because the
+ * stage-2 block descriptor will cover more than a single THP
+ * and we loose atomicity for unmapping, updates, and splits
+ * of the THP or other pages in the stage-2 block range.
+ */
+ if (vma->vm_start & ~PMD_MASK)
+ force_pte = true;
}
up_read(¤t->mm->mmap_sem);
@@ -629,6 +681,8 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
spin_lock(&kvm->mmu_lock);
if (mmu_notifier_retry(kvm, mmu_seq))
goto out_unlock;
+ if (!hugetlb && !force_pte)
+ hugetlb = transparent_hugepage_adjust(&pfn, &fault_ipa);
if (hugetlb) {
pmd_t new_pmd = pfn_pmd(pfn, PAGE_S2);
--
1.7.10.4
^ permalink raw reply related [flat|nested] 5+ messages in thread