| /* |
| * Xen mmu operations |
| * |
| * This file contains the various mmu fetch and update operations. |
| * The most important job they must perform is the mapping between the |
| * domain's pfn and the overall machine mfns. |
| * |
| * Xen allows guests to directly update the pagetable, in a controlled |
| * fashion. In other words, the guest modifies the same pagetable |
| * that the CPU actually uses, which eliminates the overhead of having |
| * a separate shadow pagetable. |
| * |
| * In order to allow this, it falls on the guest domain to map its |
| * notion of a "physical" pfn - which is just a domain-local linear |
| * address - into a real "machine address" which the CPU's MMU can |
| * use. |
| * |
| * A pgd_t/pmd_t/pte_t will typically contain an mfn, and so can be |
| * inserted directly into the pagetable. When creating a new |
| * pte/pmd/pgd, it converts the passed pfn into an mfn. Conversely, |
| * when reading the content back with __(pgd|pmd|pte)_val, it converts |
| * the mfn back into a pfn. |
| * |
| * The other constraint is that all pages which make up a pagetable |
| * must be mapped read-only in the guest. This prevents uncontrolled |
| * guest updates to the pagetable. Xen strictly enforces this, and |
| * will disallow any pagetable update which will end up mapping a |
| * pagetable page RW, and will disallow using any writable page as a |
| * pagetable. |
| * |
| * Naively, when loading %cr3 with the base of a new pagetable, Xen |
| * would need to validate the whole pagetable before going on. |
| * Naturally, this is quite slow. The solution is to "pin" a |
| * pagetable, which enforces all the constraints on the pagetable even |
| * when it is not actively in use. This menas that Xen can be assured |
| * that it is still valid when you do load it into %cr3, and doesn't |
| * need to revalidate it. |
| * |
| * Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007 |
| */ |
| #include <linux/sched.h> |
| #include <linux/highmem.h> |
| #include <linux/bug.h> |
| |
| #include <asm/pgtable.h> |
| #include <asm/tlbflush.h> |
| #include <asm/mmu_context.h> |
| #include <asm/paravirt.h> |
| |
| #include <asm/xen/hypercall.h> |
| #include <asm/xen/hypervisor.h> |
| |
| #include <xen/page.h> |
| #include <xen/interface/xen.h> |
| |
| #include "multicalls.h" |
| #include "mmu.h" |
| |
| xmaddr_t arbitrary_virt_to_machine(unsigned long address) |
| { |
| unsigned int level; |
| pte_t *pte = lookup_address(address, &level); |
| unsigned offset = address & ~PAGE_MASK; |
| |
| BUG_ON(pte == NULL); |
| |
| return XMADDR((pte_mfn(*pte) << PAGE_SHIFT) + offset); |
| } |
| |
| void make_lowmem_page_readonly(void *vaddr) |
| { |
| pte_t *pte, ptev; |
| unsigned long address = (unsigned long)vaddr; |
| unsigned int level; |
| |
| pte = lookup_address(address, &level); |
| BUG_ON(pte == NULL); |
| |
| ptev = pte_wrprotect(*pte); |
| |
| if (HYPERVISOR_update_va_mapping(address, ptev, 0)) |
| BUG(); |
| } |
| |
| void make_lowmem_page_readwrite(void *vaddr) |
| { |
| pte_t *pte, ptev; |
| unsigned long address = (unsigned long)vaddr; |
| unsigned int level; |
| |
| pte = lookup_address(address, &level); |
| BUG_ON(pte == NULL); |
| |
| ptev = pte_mkwrite(*pte); |
| |
| if (HYPERVISOR_update_va_mapping(address, ptev, 0)) |
| BUG(); |
| } |
| |
| |
| void xen_set_pmd(pmd_t *ptr, pmd_t val) |
| { |
| struct multicall_space mcs; |
| struct mmu_update *u; |
| |
| preempt_disable(); |
| |
| mcs = xen_mc_entry(sizeof(*u)); |
| u = mcs.args; |
| u->ptr = virt_to_machine(ptr).maddr; |
| u->val = pmd_val_ma(val); |
| MULTI_mmu_update(mcs.mc, u, 1, NULL, DOMID_SELF); |
| |
| xen_mc_issue(PARAVIRT_LAZY_MMU); |
| |
| preempt_enable(); |
| } |
| |
| /* |
| * Associate a virtual page frame with a given physical page frame |
| * and protection flags for that frame. |
| */ |
| void set_pte_mfn(unsigned long vaddr, unsigned long mfn, pgprot_t flags) |
| { |
| pgd_t *pgd; |
| pud_t *pud; |
| pmd_t *pmd; |
| pte_t *pte; |
| |
| pgd = swapper_pg_dir + pgd_index(vaddr); |
| if (pgd_none(*pgd)) { |
| BUG(); |
| return; |
| } |
| pud = pud_offset(pgd, vaddr); |
| if (pud_none(*pud)) { |
| BUG(); |
| return; |
| } |
| pmd = pmd_offset(pud, vaddr); |
| if (pmd_none(*pmd)) { |
| BUG(); |
| return; |
| } |
| pte = pte_offset_kernel(pmd, vaddr); |
| /* <mfn,flags> stored as-is, to permit clearing entries */ |
| xen_set_pte(pte, mfn_pte(mfn, flags)); |
| |
| /* |
| * It's enough to flush this one mapping. |
| * (PGE mappings get flushed as well) |
| */ |
| __flush_tlb_one(vaddr); |
| } |
| |
| void xen_set_pte_at(struct mm_struct *mm, unsigned long addr, |
| pte_t *ptep, pte_t pteval) |
| { |
| /* updates to init_mm may be done without lock */ |
| if (mm == &init_mm) |
| preempt_disable(); |
| |
| if (mm == current->mm || mm == &init_mm) { |
| if (paravirt_get_lazy_mode() == PARAVIRT_LAZY_MMU) { |
| struct multicall_space mcs; |
| mcs = xen_mc_entry(0); |
| |
| MULTI_update_va_mapping(mcs.mc, addr, pteval, 0); |
| xen_mc_issue(PARAVIRT_LAZY_MMU); |
| goto out; |
| } else |
| if (HYPERVISOR_update_va_mapping(addr, pteval, 0) == 0) |
| goto out; |
| } |
| xen_set_pte(ptep, pteval); |
| |
| out: |
| if (mm == &init_mm) |
| preempt_enable(); |
| } |
| |
| /* Assume pteval_t is equivalent to all the other *val_t types. */ |
| static pteval_t pte_mfn_to_pfn(pteval_t val) |
| { |
| if (val & _PAGE_PRESENT) { |
| unsigned long mfn = (val & PTE_MASK) >> PAGE_SHIFT; |
| pteval_t flags = val & ~PTE_MASK; |
| val = (mfn_to_pfn(mfn) << PAGE_SHIFT) | flags; |
| } |
| |
| return val; |
| } |
| |
| static pteval_t pte_pfn_to_mfn(pteval_t val) |
| { |
| if (val & _PAGE_PRESENT) { |
| unsigned long pfn = (val & PTE_MASK) >> PAGE_SHIFT; |
| pteval_t flags = val & ~PTE_MASK; |
| val = (pfn_to_mfn(pfn) << PAGE_SHIFT) | flags; |
| } |
| |
| return val; |
| } |
| |
| pteval_t xen_pte_val(pte_t pte) |
| { |
| return pte_mfn_to_pfn(pte.pte); |
| } |
| |
| pgdval_t xen_pgd_val(pgd_t pgd) |
| { |
| return pte_mfn_to_pfn(pgd.pgd); |
| } |
| |
| pte_t xen_make_pte(pteval_t pte) |
| { |
| pte = pte_pfn_to_mfn(pte); |
| return native_make_pte(pte); |
| } |
| |
| pgd_t xen_make_pgd(pgdval_t pgd) |
| { |
| pgd = pte_pfn_to_mfn(pgd); |
| return native_make_pgd(pgd); |
| } |
| |
| pmdval_t xen_pmd_val(pmd_t pmd) |
| { |
| return pte_mfn_to_pfn(pmd.pmd); |
| } |
| |
| void xen_set_pud(pud_t *ptr, pud_t val) |
| { |
| struct multicall_space mcs; |
| struct mmu_update *u; |
| |
| preempt_disable(); |
| |
| mcs = xen_mc_entry(sizeof(*u)); |
| u = mcs.args; |
| u->ptr = virt_to_machine(ptr).maddr; |
| u->val = pud_val_ma(val); |
| MULTI_mmu_update(mcs.mc, u, 1, NULL, DOMID_SELF); |
| |
| xen_mc_issue(PARAVIRT_LAZY_MMU); |
| |
| preempt_enable(); |
| } |
| |
| void xen_set_pte(pte_t *ptep, pte_t pte) |
| { |
| ptep->pte_high = pte.pte_high; |
| smp_wmb(); |
| ptep->pte_low = pte.pte_low; |
| } |
| |
| void xen_set_pte_atomic(pte_t *ptep, pte_t pte) |
| { |
| set_64bit((u64 *)ptep, pte_val_ma(pte)); |
| } |
| |
| void xen_pte_clear(struct mm_struct *mm, unsigned long addr, pte_t *ptep) |
| { |
| ptep->pte_low = 0; |
| smp_wmb(); /* make sure low gets written first */ |
| ptep->pte_high = 0; |
| } |
| |
| void xen_pmd_clear(pmd_t *pmdp) |
| { |
| xen_set_pmd(pmdp, __pmd(0)); |
| } |
| |
| pmd_t xen_make_pmd(pmdval_t pmd) |
| { |
| pmd = pte_pfn_to_mfn(pmd); |
| return native_make_pmd(pmd); |
| } |
| |
| /* |
| (Yet another) pagetable walker. This one is intended for pinning a |
| pagetable. This means that it walks a pagetable and calls the |
| callback function on each page it finds making up the page table, |
| at every level. It walks the entire pagetable, but it only bothers |
| pinning pte pages which are below pte_limit. In the normal case |
| this will be TASK_SIZE, but at boot we need to pin up to |
| FIXADDR_TOP. But the important bit is that we don't pin beyond |
| there, because then we start getting into Xen's ptes. |
| */ |
| static int pgd_walk(pgd_t *pgd_base, int (*func)(struct page *, enum pt_level), |
| unsigned long limit) |
| { |
| pgd_t *pgd = pgd_base; |
| int flush = 0; |
| unsigned long addr = 0; |
| unsigned long pgd_next; |
| |
| BUG_ON(limit > FIXADDR_TOP); |
| |
| if (xen_feature(XENFEAT_auto_translated_physmap)) |
| return 0; |
| |
| for (; addr != FIXADDR_TOP; pgd++, addr = pgd_next) { |
| pud_t *pud; |
| unsigned long pud_limit, pud_next; |
| |
| pgd_next = pud_limit = pgd_addr_end(addr, FIXADDR_TOP); |
| |
| if (!pgd_val(*pgd)) |
| continue; |
| |
| pud = pud_offset(pgd, 0); |
| |
| if (PTRS_PER_PUD > 1) /* not folded */ |
| flush |= (*func)(virt_to_page(pud), PT_PUD); |
| |
| for (; addr != pud_limit; pud++, addr = pud_next) { |
| pmd_t *pmd; |
| unsigned long pmd_limit; |
| |
| pud_next = pud_addr_end(addr, pud_limit); |
| |
| if (pud_next < limit) |
| pmd_limit = pud_next; |
| else |
| pmd_limit = limit; |
| |
| if (pud_none(*pud)) |
| continue; |
| |
| pmd = pmd_offset(pud, 0); |
| |
| if (PTRS_PER_PMD > 1) /* not folded */ |
| flush |= (*func)(virt_to_page(pmd), PT_PMD); |
| |
| for (; addr != pmd_limit; pmd++) { |
| addr += (PAGE_SIZE * PTRS_PER_PTE); |
| if ((pmd_limit-1) < (addr-1)) { |
| addr = pmd_limit; |
| break; |
| } |
| |
| if (pmd_none(*pmd)) |
| continue; |
| |
| flush |= (*func)(pmd_page(*pmd), PT_PTE); |
| } |
| } |
| } |
| |
| flush |= (*func)(virt_to_page(pgd_base), PT_PGD); |
| |
| return flush; |
| } |
| |
| static spinlock_t *lock_pte(struct page *page) |
| { |
| spinlock_t *ptl = NULL; |
| |
| #if NR_CPUS >= CONFIG_SPLIT_PTLOCK_CPUS |
| ptl = __pte_lockptr(page); |
| spin_lock(ptl); |
| #endif |
| |
| return ptl; |
| } |
| |
| static void do_unlock(void *v) |
| { |
| spinlock_t *ptl = v; |
| spin_unlock(ptl); |
| } |
| |
| static void xen_do_pin(unsigned level, unsigned long pfn) |
| { |
| struct mmuext_op *op; |
| struct multicall_space mcs; |
| |
| mcs = __xen_mc_entry(sizeof(*op)); |
| op = mcs.args; |
| op->cmd = level; |
| op->arg1.mfn = pfn_to_mfn(pfn); |
| MULTI_mmuext_op(mcs.mc, op, 1, NULL, DOMID_SELF); |
| } |
| |
| static int pin_page(struct page *page, enum pt_level level) |
| { |
| unsigned pgfl = TestSetPagePinned(page); |
| int flush; |
| |
| if (pgfl) |
| flush = 0; /* already pinned */ |
| else if (PageHighMem(page)) |
| /* kmaps need flushing if we found an unpinned |
| highpage */ |
| flush = 1; |
| else { |
| void *pt = lowmem_page_address(page); |
| unsigned long pfn = page_to_pfn(page); |
| struct multicall_space mcs = __xen_mc_entry(0); |
| spinlock_t *ptl; |
| |
| flush = 0; |
| |
| ptl = NULL; |
| if (level == PT_PTE) |
| ptl = lock_pte(page); |
| |
| MULTI_update_va_mapping(mcs.mc, (unsigned long)pt, |
| pfn_pte(pfn, PAGE_KERNEL_RO), |
| level == PT_PGD ? UVMF_TLB_FLUSH : 0); |
| |
| if (level == PT_PTE) |
| xen_do_pin(MMUEXT_PIN_L1_TABLE, pfn); |
| |
| if (ptl) { |
| /* Queue a deferred unlock for when this batch |
| is completed. */ |
| xen_mc_callback(do_unlock, ptl); |
| } |
| } |
| |
| return flush; |
| } |
| |
| /* This is called just after a mm has been created, but it has not |
| been used yet. We need to make sure that its pagetable is all |
| read-only, and can be pinned. */ |
| void xen_pgd_pin(pgd_t *pgd) |
| { |
| xen_mc_batch(); |
| |
| if (pgd_walk(pgd, pin_page, TASK_SIZE)) { |
| /* re-enable interrupts for kmap_flush_unused */ |
| xen_mc_issue(0); |
| kmap_flush_unused(); |
| xen_mc_batch(); |
| } |
| |
| xen_do_pin(MMUEXT_PIN_L3_TABLE, PFN_DOWN(__pa(pgd))); |
| xen_mc_issue(0); |
| } |
| |
| /* The init_mm pagetable is really pinned as soon as its created, but |
| that's before we have page structures to store the bits. So do all |
| the book-keeping now. */ |
| static __init int mark_pinned(struct page *page, enum pt_level level) |
| { |
| SetPagePinned(page); |
| return 0; |
| } |
| |
| void __init xen_mark_init_mm_pinned(void) |
| { |
| pgd_walk(init_mm.pgd, mark_pinned, FIXADDR_TOP); |
| } |
| |
| static int unpin_page(struct page *page, enum pt_level level) |
| { |
| unsigned pgfl = TestClearPagePinned(page); |
| |
| if (pgfl && !PageHighMem(page)) { |
| void *pt = lowmem_page_address(page); |
| unsigned long pfn = page_to_pfn(page); |
| spinlock_t *ptl = NULL; |
| struct multicall_space mcs; |
| |
| if (level == PT_PTE) { |
| ptl = lock_pte(page); |
| |
| xen_do_pin(MMUEXT_UNPIN_TABLE, pfn); |
| } |
| |
| mcs = __xen_mc_entry(0); |
| |
| MULTI_update_va_mapping(mcs.mc, (unsigned long)pt, |
| pfn_pte(pfn, PAGE_KERNEL), |
| level == PT_PGD ? UVMF_TLB_FLUSH : 0); |
| |
| if (ptl) { |
| /* unlock when batch completed */ |
| xen_mc_callback(do_unlock, ptl); |
| } |
| } |
| |
| return 0; /* never need to flush on unpin */ |
| } |
| |
| /* Release a pagetables pages back as normal RW */ |
| static void xen_pgd_unpin(pgd_t *pgd) |
| { |
| xen_mc_batch(); |
| |
| xen_do_pin(MMUEXT_UNPIN_TABLE, PFN_DOWN(__pa(pgd))); |
| |
| pgd_walk(pgd, unpin_page, TASK_SIZE); |
| |
| xen_mc_issue(0); |
| } |
| |
| void xen_activate_mm(struct mm_struct *prev, struct mm_struct *next) |
| { |
| spin_lock(&next->page_table_lock); |
| xen_pgd_pin(next->pgd); |
| spin_unlock(&next->page_table_lock); |
| } |
| |
| void xen_dup_mmap(struct mm_struct *oldmm, struct mm_struct *mm) |
| { |
| spin_lock(&mm->page_table_lock); |
| xen_pgd_pin(mm->pgd); |
| spin_unlock(&mm->page_table_lock); |
| } |
| |
| |
| #ifdef CONFIG_SMP |
| /* Another cpu may still have their %cr3 pointing at the pagetable, so |
| we need to repoint it somewhere else before we can unpin it. */ |
| static void drop_other_mm_ref(void *info) |
| { |
| struct mm_struct *mm = info; |
| |
| if (__get_cpu_var(cpu_tlbstate).active_mm == mm) |
| leave_mm(smp_processor_id()); |
| |
| /* If this cpu still has a stale cr3 reference, then make sure |
| it has been flushed. */ |
| if (x86_read_percpu(xen_current_cr3) == __pa(mm->pgd)) { |
| load_cr3(swapper_pg_dir); |
| arch_flush_lazy_cpu_mode(); |
| } |
| } |
| |
| static void drop_mm_ref(struct mm_struct *mm) |
| { |
| cpumask_t mask; |
| unsigned cpu; |
| |
| if (current->active_mm == mm) { |
| if (current->mm == mm) |
| load_cr3(swapper_pg_dir); |
| else |
| leave_mm(smp_processor_id()); |
| arch_flush_lazy_cpu_mode(); |
| } |
| |
| /* Get the "official" set of cpus referring to our pagetable. */ |
| mask = mm->cpu_vm_mask; |
| |
| /* It's possible that a vcpu may have a stale reference to our |
| cr3, because its in lazy mode, and it hasn't yet flushed |
| its set of pending hypercalls yet. In this case, we can |
| look at its actual current cr3 value, and force it to flush |
| if needed. */ |
| for_each_online_cpu(cpu) { |
| if (per_cpu(xen_current_cr3, cpu) == __pa(mm->pgd)) |
| cpu_set(cpu, mask); |
| } |
| |
| if (!cpus_empty(mask)) |
| smp_call_function_mask(mask, drop_other_mm_ref, mm, 1); |
| } |
| #else |
| static void drop_mm_ref(struct mm_struct *mm) |
| { |
| if (current->active_mm == mm) |
| load_cr3(swapper_pg_dir); |
| } |
| #endif |
| |
| /* |
| * While a process runs, Xen pins its pagetables, which means that the |
| * hypervisor forces it to be read-only, and it controls all updates |
| * to it. This means that all pagetable updates have to go via the |
| * hypervisor, which is moderately expensive. |
| * |
| * Since we're pulling the pagetable down, we switch to use init_mm, |
| * unpin old process pagetable and mark it all read-write, which |
| * allows further operations on it to be simple memory accesses. |
| * |
| * The only subtle point is that another CPU may be still using the |
| * pagetable because of lazy tlb flushing. This means we need need to |
| * switch all CPUs off this pagetable before we can unpin it. |
| */ |
| void xen_exit_mmap(struct mm_struct *mm) |
| { |
| get_cpu(); /* make sure we don't move around */ |
| drop_mm_ref(mm); |
| put_cpu(); |
| |
| spin_lock(&mm->page_table_lock); |
| |
| /* pgd may not be pinned in the error exit path of execve */ |
| if (PagePinned(virt_to_page(mm->pgd))) |
| xen_pgd_unpin(mm->pgd); |
| |
| spin_unlock(&mm->page_table_lock); |
| } |