[PATCH kernel v2 1/6] KVM: PPC: Avoid marking DMA-mapped pages dirty in real mode
Alexey Kardashevskiy
aik at ozlabs.ru
Mon Sep 10 18:29:07 AEST 2018
At the moment the real mode handler of H_PUT_TCE calls iommu_tce_xchg_rm()
which in turn reads the old TCE and if it was a valid entry - marks
the physical page dirty if it was mapped for writing. Since it is
the real mode, realmode_pfn_to_page() is used instead of pfn_to_page()
to get the page struct. However SetPageDirty() itself reads the compound
page head and returns a virtual address for the head page struct and
setting dirty bit for that kills the system.
This adds additional dirty bit tracking into the MM/IOMMU API for use
in the real mode. Note that this does not change how VFIO and
KVM (in virtual mode) set this bit. The KVM (real mode) changes include:
- use the lowest bit of the cached host phys address to carry
the dirty bit;
- mark pages dirty when they are unpinned which happens when
the preregistered memory is released which always happens in virtual
mode;
- add mm_iommu_ua_mark_dirty_rm() helper to set delayed dirty bit;
- change iommu_tce_xchg_rm() to take the kvm struct for the mm to use
in the new mm_iommu_ua_mark_dirty_rm() helper;
- move iommu_tce_xchg_rm() to book3s_64_vio_hv.c (which is the only
caller anyway) to reduce the real mode KVM and IOMMU knowledge
across different subsystems.
This removes realmode_pfn_to_page() as it is not used anymore.
While we at it, remove some EXPORT_SYMBOL_GPL() as that code is for
the real mode only and modules cannot call it anyway.
Signed-off-by: Alexey Kardashevskiy <aik at ozlabs.ru>
---
Changes:
v2:
* only do delaying dirtying for the real mode
* no change in VFIO IOMMU SPAPR TCE driver is needed anymore
* inverted MM_IOMMU_TABLE_GROUP_PAGE_MASK
---
arch/powerpc/include/asm/book3s/64/pgtable.h | 1 -
arch/powerpc/include/asm/iommu.h | 2 --
arch/powerpc/include/asm/mmu_context.h | 1 +
arch/powerpc/kernel/iommu.c | 25 --------------
arch/powerpc/kvm/book3s_64_vio_hv.c | 39 +++++++++++++++++-----
arch/powerpc/mm/init_64.c | 49 ----------------------------
arch/powerpc/mm/mmu_context_iommu.c | 34 ++++++++++++++++---
7 files changed, 62 insertions(+), 89 deletions(-)
diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index 13a688f..2fdc865 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -1051,7 +1051,6 @@ static inline void vmemmap_remove_mapping(unsigned long start,
return hash__vmemmap_remove_mapping(start, page_size);
}
#endif
-struct page *realmode_pfn_to_page(unsigned long pfn);
static inline pte_t pmd_pte(pmd_t pmd)
{
diff --git a/arch/powerpc/include/asm/iommu.h b/arch/powerpc/include/asm/iommu.h
index ab3a4fb..3d4b88c 100644
--- a/arch/powerpc/include/asm/iommu.h
+++ b/arch/powerpc/include/asm/iommu.h
@@ -220,8 +220,6 @@ extern void iommu_del_device(struct device *dev);
extern int __init tce_iommu_bus_notifier_init(void);
extern long iommu_tce_xchg(struct iommu_table *tbl, unsigned long entry,
unsigned long *hpa, enum dma_data_direction *direction);
-extern long iommu_tce_xchg_rm(struct iommu_table *tbl, unsigned long entry,
- unsigned long *hpa, enum dma_data_direction *direction);
#else
static inline void iommu_register_group(struct iommu_table_group *table_group,
int pci_domain_number,
diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/include/asm/mmu_context.h
index b2f89b6..b694d6a 100644
--- a/arch/powerpc/include/asm/mmu_context.h
+++ b/arch/powerpc/include/asm/mmu_context.h
@@ -38,6 +38,7 @@ extern long mm_iommu_ua_to_hpa(struct mm_iommu_table_group_mem_t *mem,
unsigned long ua, unsigned int pageshift, unsigned long *hpa);
extern long mm_iommu_ua_to_hpa_rm(struct mm_iommu_table_group_mem_t *mem,
unsigned long ua, unsigned int pageshift, unsigned long *hpa);
+extern void mm_iommu_ua_mark_dirty_rm(struct mm_struct *mm, unsigned long ua);
extern long mm_iommu_mapped_inc(struct mm_iommu_table_group_mem_t *mem);
extern void mm_iommu_mapped_dec(struct mm_iommu_table_group_mem_t *mem);
#endif
diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
index af7a20d..19b4c62 100644
--- a/arch/powerpc/kernel/iommu.c
+++ b/arch/powerpc/kernel/iommu.c
@@ -1013,31 +1013,6 @@ long iommu_tce_xchg(struct iommu_table *tbl, unsigned long entry,
}
EXPORT_SYMBOL_GPL(iommu_tce_xchg);
-#ifdef CONFIG_PPC_BOOK3S_64
-long iommu_tce_xchg_rm(struct iommu_table *tbl, unsigned long entry,
- unsigned long *hpa, enum dma_data_direction *direction)
-{
- long ret;
-
- ret = tbl->it_ops->exchange_rm(tbl, entry, hpa, direction);
-
- if (!ret && ((*direction == DMA_FROM_DEVICE) ||
- (*direction == DMA_BIDIRECTIONAL))) {
- struct page *pg = realmode_pfn_to_page(*hpa >> PAGE_SHIFT);
-
- if (likely(pg)) {
- SetPageDirty(pg);
- } else {
- tbl->it_ops->exchange_rm(tbl, entry, hpa, direction);
- ret = -EFAULT;
- }
- }
-
- return ret;
-}
-EXPORT_SYMBOL_GPL(iommu_tce_xchg_rm);
-#endif
-
int iommu_take_ownership(struct iommu_table *tbl)
{
unsigned long flags, i, sz = (tbl->it_size + 7) >> 3;
diff --git a/arch/powerpc/kvm/book3s_64_vio_hv.c b/arch/powerpc/kvm/book3s_64_vio_hv.c
index 506a4d4..6821ead 100644
--- a/arch/powerpc/kvm/book3s_64_vio_hv.c
+++ b/arch/powerpc/kvm/book3s_64_vio_hv.c
@@ -187,12 +187,35 @@ long kvmppc_gpa_to_ua(struct kvm *kvm, unsigned long gpa,
EXPORT_SYMBOL_GPL(kvmppc_gpa_to_ua);
#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
-static void kvmppc_rm_clear_tce(struct iommu_table *tbl, unsigned long entry)
+static long iommu_tce_xchg_rm(struct mm_struct *mm, struct iommu_table *tbl,
+ unsigned long entry, unsigned long *hpa,
+ enum dma_data_direction *direction)
+{
+ long ret;
+
+ ret = tbl->it_ops->exchange_rm(tbl, entry, hpa, direction);
+
+ if (!ret && ((*direction == DMA_FROM_DEVICE) ||
+ (*direction == DMA_BIDIRECTIONAL))) {
+ __be64 *pua = IOMMU_TABLE_USERSPACE_ENTRY_RM(tbl, entry);
+ /*
+ * kvmppc_rm_tce_iommu_do_map() updates the UA cache after
+ * calling this so we still get here a valid UA.
+ */
+ if (pua && *pua)
+ mm_iommu_ua_mark_dirty_rm(mm, be64_to_cpu(*pua));
+ }
+
+ return ret;
+}
+
+static void kvmppc_rm_clear_tce(struct kvm *kvm, struct iommu_table *tbl,
+ unsigned long entry)
{
unsigned long hpa = 0;
enum dma_data_direction dir = DMA_NONE;
- iommu_tce_xchg_rm(tbl, entry, &hpa, &dir);
+ iommu_tce_xchg_rm(kvm->mm, tbl, entry, &hpa, &dir);
}
static long kvmppc_rm_tce_iommu_mapped_dec(struct kvm *kvm,
@@ -224,7 +247,7 @@ static long kvmppc_rm_tce_iommu_do_unmap(struct kvm *kvm,
unsigned long hpa = 0;
long ret;
- if (iommu_tce_xchg_rm(tbl, entry, &hpa, &dir))
+ if (iommu_tce_xchg_rm(kvm->mm, tbl, entry, &hpa, &dir))
/*
* real mode xchg can fail if struct page crosses
* a page boundary
@@ -236,7 +259,7 @@ static long kvmppc_rm_tce_iommu_do_unmap(struct kvm *kvm,
ret = kvmppc_rm_tce_iommu_mapped_dec(kvm, tbl, entry);
if (ret)
- iommu_tce_xchg_rm(tbl, entry, &hpa, &dir);
+ iommu_tce_xchg_rm(kvm->mm, tbl, entry, &hpa, &dir);
return ret;
}
@@ -282,7 +305,7 @@ static long kvmppc_rm_tce_iommu_do_map(struct kvm *kvm, struct iommu_table *tbl,
if (WARN_ON_ONCE_RM(mm_iommu_mapped_inc(mem)))
return H_CLOSED;
- ret = iommu_tce_xchg_rm(tbl, entry, &hpa, &dir);
+ ret = iommu_tce_xchg_rm(kvm->mm, tbl, entry, &hpa, &dir);
if (ret) {
mm_iommu_mapped_dec(mem);
/*
@@ -371,7 +394,7 @@ long kvmppc_rm_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
return ret;
WARN_ON_ONCE_RM(1);
- kvmppc_rm_clear_tce(stit->tbl, entry);
+ kvmppc_rm_clear_tce(vcpu->kvm, stit->tbl, entry);
}
kvmppc_tce_put(stt, entry, tce);
@@ -520,7 +543,7 @@ long kvmppc_rm_h_put_tce_indirect(struct kvm_vcpu *vcpu,
goto unlock_exit;
WARN_ON_ONCE_RM(1);
- kvmppc_rm_clear_tce(stit->tbl, entry);
+ kvmppc_rm_clear_tce(vcpu->kvm, stit->tbl, entry);
}
kvmppc_tce_put(stt, entry + i, tce);
@@ -571,7 +594,7 @@ long kvmppc_rm_h_stuff_tce(struct kvm_vcpu *vcpu,
return ret;
WARN_ON_ONCE_RM(1);
- kvmppc_rm_clear_tce(stit->tbl, entry);
+ kvmppc_rm_clear_tce(vcpu->kvm, stit->tbl, entry);
}
}
diff --git a/arch/powerpc/mm/init_64.c b/arch/powerpc/mm/init_64.c
index 51ce091..7a9886f 100644
--- a/arch/powerpc/mm/init_64.c
+++ b/arch/powerpc/mm/init_64.c
@@ -308,55 +308,6 @@ void register_page_bootmem_memmap(unsigned long section_nr,
{
}
-/*
- * We do not have access to the sparsemem vmemmap, so we fallback to
- * walking the list of sparsemem blocks which we already maintain for
- * the sake of crashdump. In the long run, we might want to maintain
- * a tree if performance of that linear walk becomes a problem.
- *
- * realmode_pfn_to_page functions can fail due to:
- * 1) As real sparsemem blocks do not lay in RAM continously (they
- * are in virtual address space which is not available in the real mode),
- * the requested page struct can be split between blocks so get_page/put_page
- * may fail.
- * 2) When huge pages are used, the get_page/put_page API will fail
- * in real mode as the linked addresses in the page struct are virtual
- * too.
- */
-struct page *realmode_pfn_to_page(unsigned long pfn)
-{
- struct vmemmap_backing *vmem_back;
- struct page *page;
- unsigned long page_size = 1 << mmu_psize_defs[mmu_vmemmap_psize].shift;
- unsigned long pg_va = (unsigned long) pfn_to_page(pfn);
-
- for (vmem_back = vmemmap_list; vmem_back; vmem_back = vmem_back->list) {
- if (pg_va < vmem_back->virt_addr)
- continue;
-
- /* After vmemmap_list entry free is possible, need check all */
- if ((pg_va + sizeof(struct page)) <=
- (vmem_back->virt_addr + page_size)) {
- page = (struct page *) (vmem_back->phys + pg_va -
- vmem_back->virt_addr);
- return page;
- }
- }
-
- /* Probably that page struct is split between real pages */
- return NULL;
-}
-EXPORT_SYMBOL_GPL(realmode_pfn_to_page);
-
-#else
-
-struct page *realmode_pfn_to_page(unsigned long pfn)
-{
- struct page *page = pfn_to_page(pfn);
- return page;
-}
-EXPORT_SYMBOL_GPL(realmode_pfn_to_page);
-
#endif /* CONFIG_SPARSEMEM_VMEMMAP */
#ifdef CONFIG_PPC_BOOK3S_64
diff --git a/arch/powerpc/mm/mmu_context_iommu.c b/arch/powerpc/mm/mmu_context_iommu.c
index c9ee9e2..56c2234 100644
--- a/arch/powerpc/mm/mmu_context_iommu.c
+++ b/arch/powerpc/mm/mmu_context_iommu.c
@@ -18,11 +18,15 @@
#include <linux/migrate.h>
#include <linux/hugetlb.h>
#include <linux/swap.h>
+#include <linux/sizes.h>
#include <asm/mmu_context.h>
#include <asm/pte-walk.h>
static DEFINE_MUTEX(mem_list_mutex);
+#define MM_IOMMU_TABLE_GROUP_PAGE_DIRTY 0x1
+#define MM_IOMMU_TABLE_GROUP_PAGE_MASK ~(SZ_4K - 1)
+
struct mm_iommu_table_group_mem_t {
struct list_head next;
struct rcu_head rcu;
@@ -263,6 +267,9 @@ static void mm_iommu_unpin(struct mm_iommu_table_group_mem_t *mem)
if (!page)
continue;
+ if (mem->hpas[i] & MM_IOMMU_TABLE_GROUP_PAGE_DIRTY)
+ SetPageDirty(page);
+
put_page(page);
mem->hpas[i] = 0;
}
@@ -360,7 +367,6 @@ struct mm_iommu_table_group_mem_t *mm_iommu_lookup_rm(struct mm_struct *mm,
return ret;
}
-EXPORT_SYMBOL_GPL(mm_iommu_lookup_rm);
struct mm_iommu_table_group_mem_t *mm_iommu_find(struct mm_struct *mm,
unsigned long ua, unsigned long entries)
@@ -390,7 +396,7 @@ long mm_iommu_ua_to_hpa(struct mm_iommu_table_group_mem_t *mem,
if (pageshift > mem->pageshift)
return -EFAULT;
- *hpa = *va | (ua & ~PAGE_MASK);
+ *hpa = (*va & MM_IOMMU_TABLE_GROUP_PAGE_MASK) | (ua & ~PAGE_MASK);
return 0;
}
@@ -413,11 +419,31 @@ long mm_iommu_ua_to_hpa_rm(struct mm_iommu_table_group_mem_t *mem,
if (!pa)
return -EFAULT;
- *hpa = *pa | (ua & ~PAGE_MASK);
+ *hpa = (*pa & MM_IOMMU_TABLE_GROUP_PAGE_MASK) | (ua & ~PAGE_MASK);
return 0;
}
-EXPORT_SYMBOL_GPL(mm_iommu_ua_to_hpa_rm);
+
+extern void mm_iommu_ua_mark_dirty_rm(struct mm_struct *mm, unsigned long ua)
+{
+ struct mm_iommu_table_group_mem_t *mem;
+ long entry;
+ void *va;
+ unsigned long *pa;
+
+ mem = mm_iommu_lookup_rm(mm, ua, PAGE_SIZE);
+ if (!mem)
+ return;
+
+ entry = (ua - mem->ua) >> PAGE_SHIFT;
+ va = &mem->hpas[entry];
+
+ pa = (void *) vmalloc_to_phys(va);
+ if (!pa)
+ return;
+
+ *pa |= MM_IOMMU_TABLE_GROUP_PAGE_DIRTY;
+}
long mm_iommu_mapped_inc(struct mm_iommu_table_group_mem_t *mem)
{
--
2.11.0
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