Add support for KVM faulting of daxfd through using dax_direct_access(). The function kvm_dax_get_pfn() is implemented to complete the daxfd support for KVM faulting. A reference is taken on the page. There is no need to call put_dev_pagemap() when put_page() happens as recent kernel changes takes care of that within put_page() path.
Signed-off-by: Dave Jiang <[email protected]> --- arch/x86/kvm/mmu/mmu.c | 48 +++++++++++++++++++++++++++++++++++----- drivers/dax/bus.c | 1 + include/linux/dax.h | 1 + include/linux/kvm_host.h | 8 +++++++ virt/kvm/guest_memfd.c | 42 +++++++++++++++++++++++++++++++++++ 5 files changed, 94 insertions(+), 6 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 02c450686b4a..fe787f73b9a8 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -4588,16 +4588,52 @@ static int kvm_mmu_faultin_pfn_gmem(struct kvm_vcpu *vcpu, return RET_PF_CONTINUE; } +static pgoff_t kvm_gmem_get_index(struct kvm_memory_slot *slot, gfn_t gfn) +{ + return gfn - slot->base_gfn + slot->gmem.pgoff; +} + +static kvm_pfn_t kvm_faultin_dax_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) +{ + kvm_pfn_t pfn; + pgoff_t index; + int rc; + + if (!kvm_memslot_is_dax_only(fault->slot)) + return KVM_PFN_ERR_FAULT; + + index = kvm_gmem_get_index(fault->slot, fault->gfn); + rc = kvm_dax_get_pfn(fault->slot, index, &pfn, &fault->refcounted_page); + if (rc) + return KVM_PFN_ERR_FAULT; + + return pfn; +} + static int __kvm_mmu_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) { unsigned int foll = fault->write ? FOLL_WRITE : 0; + gfn_t gfn = fault->gfn; - if (fault->is_private || kvm_memslot_is_gmem_only(fault->slot)) + if (fault->is_private || (kvm_memslot_is_gmem_only(fault->slot) && + !kvm_memslot_is_dax_only(fault->slot))) return kvm_mmu_faultin_pfn_gmem(vcpu, fault); + if (kvm_memslot_is_dax_only(fault->slot)) { + gfn = kvm_gmem_get_index(fault->slot, fault->gfn); + fault->pfn = kvm_faultin_dax_pfn(vcpu, fault); + if (fault->pfn == KVM_PFN_ERR_FAULT) { + kvm_mmu_prepare_memory_fault_exit(vcpu, fault); + return RET_PF_INVALID; + } + fault->map_writable = !(fault->slot->flags & KVM_MEM_READONLY); + + return RET_PF_CONTINUE; + } + foll |= FOLL_NOWAIT; - fault->pfn = __kvm_faultin_pfn(fault->slot, fault->gfn, foll, + fault->pfn = __kvm_faultin_pfn(fault->slot, gfn, foll, &fault->map_writable, &fault->refcounted_page); /* @@ -4610,9 +4646,9 @@ static int __kvm_mmu_faultin_pfn(struct kvm_vcpu *vcpu, return RET_PF_CONTINUE; if (!fault->prefetch && kvm_can_do_async_pf(vcpu)) { - trace_kvm_try_async_get_page(fault->addr, fault->gfn); - if (kvm_find_async_pf_gfn(vcpu, fault->gfn)) { - trace_kvm_async_pf_repeated_fault(fault->addr, fault->gfn); + trace_kvm_try_async_get_page(fault->addr, gfn); + if (kvm_find_async_pf_gfn(vcpu, gfn)) { + trace_kvm_async_pf_repeated_fault(fault->addr, gfn); kvm_make_request(KVM_REQ_APF_HALT, vcpu); return RET_PF_RETRY; } else if (kvm_arch_setup_async_pf(vcpu, fault)) { @@ -4627,7 +4663,7 @@ static int __kvm_mmu_faultin_pfn(struct kvm_vcpu *vcpu, */ foll |= FOLL_INTERRUPTIBLE; foll &= ~FOLL_NOWAIT; - fault->pfn = __kvm_faultin_pfn(fault->slot, fault->gfn, foll, + fault->pfn = __kvm_faultin_pfn(fault->slot, gfn, foll, &fault->map_writable, &fault->refcounted_page); return RET_PF_CONTINUE; diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c index a99db3739e45..2009f34614d8 100644 --- a/drivers/dax/bus.c +++ b/drivers/dax/bus.c @@ -2,6 +2,7 @@ /* Copyright(c) 2017-2018 Intel Corporation. All rights reserved. */ #include <linux/memremap.h> #include <linux/highmem.h> +#include <linux/kvm_host.h> #include <linux/device.h> #include <linux/mutex.h> #include <linux/list.h> diff --git a/include/linux/dax.h b/include/linux/dax.h index da1413c8a21f..41214b6d7897 100644 --- a/include/linux/dax.h +++ b/include/linux/dax.h @@ -5,6 +5,7 @@ #include <linux/fs.h> #include <linux/mm.h> #include <linux/radix-tree.h> +#include <linux/kvm_host.h> typedef unsigned long dax_entry_t; diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 9afce6d02d9e..ffd0381ba079 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -2552,6 +2552,8 @@ static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn) int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, gfn_t gfn, kvm_pfn_t *pfn, struct page **page, int *max_order); +int kvm_dax_get_pfn(struct kvm_memory_slot *slot, pgoff_t index, kvm_pfn_t *pfn, + struct page **refcounted_page); #else static inline int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, gfn_t gfn, @@ -2561,6 +2563,12 @@ static inline int kvm_gmem_get_pfn(struct kvm *kvm, KVM_BUG_ON(1, kvm); return -EIO; } +static inline int kvm_dax_get_pfn(struct kvm_memory_slot *slot, gfn_t gfn, + kvm_pfn_t *pfn) +{ + KVM_BUG_ON(1, kvm); + return -EIO; +} #endif /* CONFIG_KVM_GUEST_MEMFD */ #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_PREPARE diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index 959f690c1d1d..4e7141fdb2b8 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -840,6 +840,48 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, } EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_gmem_get_pfn); +int kvm_dax_get_pfn(struct kvm_memory_slot *slot, pgoff_t index, kvm_pfn_t *pfn, + struct page **refcounted_page) +{ + struct dev_pagemap *pgmap; + struct dev_dax *dev_dax; + struct page *page; + void *kaddr; + long rc; + int id; + + CLASS(gmem_get_file, file)(slot); + if (!file) + return -EFAULT; + + dev_dax = file->private_data; + if (!dev_dax) + return -ENODEV; + + id = dax_read_lock(); + rc = dax_direct_access(dax_get_dev_dax(dev_dax), index, 1, DAX_ACCESS, + &kaddr, (unsigned long *)pfn); + dax_read_unlock(id); + if (rc < 0) + return rc; + + /* Verify that 'struct page' exists for this PFN */ + pgmap = get_dev_pagemap(*pfn); + if (!pgmap) + return -ENODEV; + + page = pfn_to_page(*pfn); + if (!try_get_page(page)) { + put_dev_pagemap(pgmap); + return -EFAULT; + } + + *refcounted_page = page; + + return 0; +} +EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_dax_get_pfn); + #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_POPULATE long kvm_gmem_populate(struct kvm *kvm, gfn_t start_gfn, void __user *src, long npages, kvm_gmem_populate_cb post_populate, void *opaque) -- 2.53.0
