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Commit 425333bf authored by Alexey Kardashevskiy's avatar Alexey Kardashevskiy Committed by Paul Mackerras
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KVM: PPC: Avoid marking DMA-mapped pages dirty in real mode 



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 in
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: default avatarAlexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: default avatarDavid Gibson <david@gibson.dropbear.id.au>
Signed-off-by: default avatarPaul Mackerras <paulus@ozlabs.org>
parent bdf7ffc8

arch/powerpc/include/asm/book3s/64/pgtable.h

+0 −1
Original line number Diff line number Diff line
@@ -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)

{

arch/powerpc/include/asm/iommu.h

+0 −2
Original line number Diff line number Diff line
@@ -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,

arch/powerpc/include/asm/mmu_context.h

+1 −0
Original line number Diff line number Diff line
@@ -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

arch/powerpc/kernel/iommu.c

+0 −25
Original line number Diff line number Diff line
@@ -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;

arch/powerpc/kvm/book3s_64_vio_hv.c

+31 −8
Original line number Diff line number Diff line
@@ -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);

		}

	}