Messages in this thread | | | Subject | Re: [PATCH 04/10] KVM: Introduce a new guest mapping API | From | Paolo Bonzini <> | Date | Thu, 12 Apr 2018 16:33:08 +0200 |
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Coming back to this (nice) series.
On 21/02/2018 18:47, KarimAllah Ahmed wrote: > +bool kvm_vcpu_map(struct kvm_vcpu *vcpu, gfn_t gfn, struct kvm_host_map *map) > +{ > + kvm_pfn_t pfn; > + void *kaddr = NULL;
Can we s/kaddr/hva/ since that's the standard nomenclature?
> + struct page *page = NULL; > + > + if (map->kaddr && map->gfn == gfn) > + /* If the mapping is valid and guest memory is already mapped */ > + return true;
Please return 0/-EINVAL instead. More important, this optimization is problematic because:
1) the underlying memslots array could have changed. You'd also need to store the generation count (see kvm_read_guest_cached for an example)
2) worse, the memslots array could have switched between the SMM and non-SMM address spaces. This is by the way the reason why there is no kvm_vcpu_read_guest_cached API.
However, all the places you're changing in patches 4-10 are doing already kvm_vcpu_gpa_to_page, so I suggest just dropping this optimization.
> + else if (map->kaddr) > + /* If the mapping is valid but trying to map a different guest pfn */ > + kvm_vcpu_unmap(map); > + > + pfn = kvm_vcpu_gfn_to_pfn(vcpu, gfn);
Please change the API to:
static int __kvm_map_gfn(struct kvm_memslot *memslots, gfn_t gfn, struct kvm_host_map *map)
calling gfn_to_pfn_memslot(memslots, gfn)
int kvm_vcpu_map_gfn(struct kvm_vcpu *vcpu gfn_t gfn, struct kvm_host_map *map)
calling kvm_vcpu_gfn_to_memslot + __kvm_map
void kvm_unmap_gfn(struct kvm_host_map *map)
> + if (is_error_pfn(pfn)) > + return false;
Should this be is_error_noslot_pfn?
> + if (pfn_valid(pfn)) { > + page = pfn_to_page(pfn); > + kaddr = vmap(&page, 1, VM_MAP, PAGE_KERNEL); > + } else { > + kaddr = memremap(pfn_to_hpa(pfn), PAGE_SIZE, MEMREMAP_WB); > + } > + > + if (!kaddr) > + return false; > + > + map->page = page; > + map->kaddr = kaddr; > + map->pfn = pfn; > + map->gfn = gfn; > + > + return true; > +}
> > +void kvm_vcpu_unmap(struct kvm_host_map *map) > +{ > + if (!map->kaddr) > + return; > + > + if (map->page) > + kunmap(map->page); > + else > + memunmap(map->kaddr); > + > + kvm_release_pfn_dirty(map->pfn); > + memset(map, 0, sizeof(*map));
This can clear just map->kaddr (map->hva after the above review).
Thanks,
Paolo
> +} > +
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