From 6dd761d92f6600342860c618639489bb9c3843ea Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Thu, 11 Jul 2024 18:27:50 -0400 Subject: [PATCH] KVM: guest_memfd: make kvm_gmem_prepare_folio() operate on a single struct kvm This is now possible because preparation is done by kvm_gmem_get_pfn() instead of fallocate(). In practice this is not a limitation, because even though guest_memfd can be bound to multiple struct kvm, for hardware implementations of confidential computing only one guest (identified by an ASID on SEV-SNP, or an HKID on TDX) will be able to access it. In the case of intra-host migration (not implemented yet for SEV-SNP, but we can use SEV-ES as an idea of how it will work), the new struct kvm inherits the same ASID and preparation need not be repeated. Reviewed-by: Michael Roth Signed-off-by: Paolo Bonzini --- virt/kvm/guest_memfd.c | 47 ++++++++++++++++-------------------------- 1 file changed, 18 insertions(+), 29 deletions(-) diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index 5af278c7adba..444ded162154 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -25,37 +25,27 @@ static inline kvm_pfn_t folio_file_pfn(struct folio *folio, pgoff_t index) return folio_pfn(folio) + (index & (folio_nr_pages(folio) - 1)); } -static int __kvm_gmem_prepare_folio(struct inode *inode, pgoff_t index, struct folio *folio) +static int __kvm_gmem_prepare_folio(struct kvm *kvm, struct kvm_memory_slot *slot, + pgoff_t index, struct folio *folio) { #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_PREPARE - struct list_head *gmem_list = &inode->i_mapping->i_private_list; - struct kvm_gmem *gmem; + kvm_pfn_t pfn; + gfn_t gfn; + int rc; - list_for_each_entry(gmem, gmem_list, entry) { - struct kvm_memory_slot *slot; - struct kvm *kvm = gmem->kvm; - kvm_pfn_t pfn; - gfn_t gfn; - int rc; + if (!kvm_arch_gmem_prepare_needed(kvm)) + return 0; - if (!kvm_arch_gmem_prepare_needed(kvm)) - continue; - - slot = xa_load(&gmem->bindings, index); - if (!slot) - continue; - - pfn = folio_file_pfn(folio, index); - gfn = slot->base_gfn + index - slot->gmem.pgoff; - rc = kvm_arch_gmem_prepare(kvm, gfn, pfn, folio_order(folio)); - if (rc) { - pr_warn_ratelimited("gmem: Failed to prepare folio for GFN %llx PFN %llx error %d.\n", - gfn, pfn, rc); - return rc; - } + pfn = folio_file_pfn(folio, index); + gfn = slot->base_gfn + index - slot->gmem.pgoff; + rc = kvm_arch_gmem_prepare(kvm, gfn, pfn, folio_order(folio)); + if (rc) { + pr_warn_ratelimited("gmem: Failed to prepare folio for index %lx GFN %llx PFN %llx error %d.\n", + index, gfn, pfn, rc); + return rc; } - #endif + return 0; } @@ -65,7 +55,7 @@ static int __kvm_gmem_prepare_folio(struct inode *inode, pgoff_t index, struct f * On successful return the guest sees a zero page so as to avoid * leaking host data and the up-to-date flag is set. */ -static int kvm_gmem_prepare_folio(struct file *file, struct kvm_memory_slot *slot, +static int kvm_gmem_prepare_folio(struct kvm *kvm, struct kvm_memory_slot *slot, gfn_t gfn, struct folio *folio) { unsigned long nr_pages, i; @@ -95,8 +85,7 @@ static int kvm_gmem_prepare_folio(struct file *file, struct kvm_memory_slot *slo WARN_ON(!IS_ALIGNED(slot->gmem.pgoff, 1 << folio_order(folio))); index = gfn - slot->base_gfn + slot->gmem.pgoff; index = ALIGN_DOWN(index, 1 << folio_order(folio)); - - r = __kvm_gmem_prepare_folio(file_inode(file), index, folio); + r = __kvm_gmem_prepare_folio(kvm, slot, index, folio); if (!r) folio_mark_uptodate(folio); @@ -619,7 +608,7 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, goto out; } - r = kvm_gmem_prepare_folio(file, slot, gfn, folio); + r = kvm_gmem_prepare_folio(kvm, slot, gfn, folio); folio_unlock(folio); if (r < 0) folio_put(folio);