static int stage2_set_pmd_huge(struct kvm *kvm, struct kvm_mmu_memory_cache
*cache, phys_addr_t addr, const pmd_t *new_pmd)
{
pmd_t *pmd, old_pmd;
pmd = stage2_get_pmd(kvm, cache, addr);
VM_BUG_ON(!pmd);
/*
* Mapping in huge pages should only happen through a fault. If a
* page is merged into a transparent huge page, the individual
* subpages of that huge page should be unmapped through MMU
* notifiers before we get here.
*
* Merging of CompoundPages is not supported; they should become
* splitting first, unmapped, merged, and mapped back in on-demand.
*/
VM_BUG_ON(pmd_present(*pmd) && pmd_pfn(*pmd) != pmd_pfn(*new_pmd));
old_pmd = *pmd;
kvm_set_pmd(pmd, *new_pmd);
if (pmd_present(old_pmd))
kvm_tlb_flush_vmid_ipa(kvm, addr);
else
get_page(virt_to_page(pmd));
return 0;
}
static int stage2_set_pmd_huge(struct kvm *kvm, struct kvm_mmu_memory_cache
*cache, phys_addr_t addr, const pmd_t *new_pmd)
{
pmd_t *pmd, old_pmd;
pmd = stage2_get_pmd(kvm, cache, addr);
VM_BUG_ON(!pmd);
old_pmd = *pmd;
if (pmd_present(old_pmd)) {
/*
* Multiple vcpus faulting on the same PMD entry, can
* lead to them sequentially updating the PMD with the
* same value. Following the break-before-make
* (pmd_clear() followed by tlb_flush()) process can
* hinder forward progress due to refaults generated
* on missing translations.
*
* Skip updating the page table if the entry is
* unchanged.
*/
if (pmd_val(old_pmd) == pmd_val(*new_pmd))
return 0;
/*
* Mapping in huge pages should only happen through a
* fault. If a page is merged into a transparent huge
* page, the individual subpages of that huge page
* should be unmapped through MMU notifiers before we
* get here.
*
* Merging of CompoundPages is not supported; they
* should become splitting first, unmapped, merged,
* and mapped back in on-demand.
*/
VM_BUG_ON(pmd_pfn(old_pmd) != pmd_pfn(*new_pmd));
pmd_clear(pmd);
kvm_tlb_flush_vmid_ipa(kvm, addr);
} else {
get_page(virt_to_page(pmd));
}
kvm_set_pmd(pmd, *new_pmd);
return 0;
}