From e45adf665a53df0db37f784ed87c6b57ddd81885 Mon Sep 17 00:00:00 2001 From: KarimAllah Ahmed Date: Thu, 31 Jan 2019 21:24:34 +0100 Subject: KVM: Introduce a new guest mapping API In KVM, specially for nested guests, there is a dominant pattern of: => map guest memory -> do_something -> unmap guest memory In addition to all this unnecessarily noise in the code due to boiler plate code, most of the time the mapping function does not properly handle memory that is not backed by "struct page". This new guest mapping API encapsulate most of this boiler plate code and also handles guest memory that is not backed by "struct page". The current implementation of this API is using memremap for memory that is not backed by a "struct page" which would lead to a huge slow-down if it was used for high-frequency mapping operations. The API does not have any effect on current setups where guest memory is backed by a "struct page". Further patches are going to also introduce a pfn-cache which would significantly improve the performance of the memremap case. Signed-off-by: KarimAllah Ahmed Reviewed-by: Konrad Rzeszutek Wilk Signed-off-by: Paolo Bonzini --- virt/kvm/kvm_main.c | 64 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 64 insertions(+) (limited to 'virt') diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 3194aa3d0b43..53de2f946f9e 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -1742,6 +1742,70 @@ struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn) } EXPORT_SYMBOL_GPL(gfn_to_page); +static int __kvm_map_gfn(struct kvm_memory_slot *slot, gfn_t gfn, + struct kvm_host_map *map) +{ + kvm_pfn_t pfn; + void *hva = NULL; + struct page *page = KVM_UNMAPPED_PAGE; + + if (!map) + return -EINVAL; + + pfn = gfn_to_pfn_memslot(slot, gfn); + if (is_error_noslot_pfn(pfn)) + return -EINVAL; + + if (pfn_valid(pfn)) { + page = pfn_to_page(pfn); + hva = kmap(page); + } else { + hva = memremap(pfn_to_hpa(pfn), PAGE_SIZE, MEMREMAP_WB); + } + + if (!hva) + return -EFAULT; + + map->page = page; + map->hva = hva; + map->pfn = pfn; + map->gfn = gfn; + + return 0; +} + +int kvm_vcpu_map(struct kvm_vcpu *vcpu, gfn_t gfn, struct kvm_host_map *map) +{ + return __kvm_map_gfn(kvm_vcpu_gfn_to_memslot(vcpu, gfn), gfn, map); +} +EXPORT_SYMBOL_GPL(kvm_vcpu_map); + +void kvm_vcpu_unmap(struct kvm_vcpu *vcpu, struct kvm_host_map *map, + bool dirty) +{ + if (!map) + return; + + if (!map->hva) + return; + + if (map->page) + kunmap(map->page); + else + memunmap(map->hva); + + if (dirty) { + kvm_vcpu_mark_page_dirty(vcpu, map->gfn); + kvm_release_pfn_dirty(map->pfn); + } else { + kvm_release_pfn_clean(map->pfn); + } + + map->hva = NULL; + map->page = NULL; +} +EXPORT_SYMBOL_GPL(kvm_vcpu_unmap); + struct page *kvm_vcpu_gfn_to_page(struct kvm_vcpu *vcpu, gfn_t gfn) { kvm_pfn_t pfn; -- cgit v1.2.3