From 9702785a747aa27baf46ff504beab6528f21f2dd Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Thu, 11 Oct 2007 11:16:51 +0200 Subject: i386: move xen Signed-off-by: Thomas Gleixner Signed-off-by: Ingo Molnar --- arch/x86/xen/mmu.c | 567 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 567 insertions(+) create mode 100644 arch/x86/xen/mmu.c (limited to 'arch/x86/xen/mmu.c') diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c new file mode 100644 index 000000000000..874db0cd1d2a --- /dev/null +++ b/arch/x86/xen/mmu.c @@ -0,0 +1,567 @@ +/* + * 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 , XenSource Inc, 2007 + */ +#include +#include +#include +#include + +#include +#include +#include +#include + +#include +#include + +#include +#include + +#include "multicalls.h" +#include "mmu.h" + +xmaddr_t arbitrary_virt_to_machine(unsigned long address) +{ + pte_t *pte = lookup_address(address); + 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; + + pte = lookup_address(address); + 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; + + pte = lookup_address(address); + 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); + /* 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) +{ + if (mm == current->mm || mm == &init_mm) { + if (xen_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); + return; + } else + if (HYPERVISOR_update_va_mapping(addr, pteval, 0) == 0) + return; + } + xen_set_pte(ptep, pteval); +} + +#ifdef CONFIG_X86_PAE +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)); +} + +unsigned long long xen_pte_val(pte_t pte) +{ + unsigned long long ret = 0; + + if (pte.pte_low) { + ret = ((unsigned long long)pte.pte_high << 32) | pte.pte_low; + ret = machine_to_phys(XMADDR(ret)).paddr | 1; + } + + return ret; +} + +unsigned long long xen_pmd_val(pmd_t pmd) +{ + unsigned long long ret = pmd.pmd; + if (ret) + ret = machine_to_phys(XMADDR(ret)).paddr | 1; + return ret; +} + +unsigned long long xen_pgd_val(pgd_t pgd) +{ + unsigned long long ret = pgd.pgd; + if (ret) + ret = machine_to_phys(XMADDR(ret)).paddr | 1; + return ret; +} + +pte_t xen_make_pte(unsigned long long pte) +{ + if (pte & 1) + pte = phys_to_machine(XPADDR(pte)).maddr; + + return (pte_t){ pte, pte >> 32 }; +} + +pmd_t xen_make_pmd(unsigned long long pmd) +{ + if (pmd & 1) + pmd = phys_to_machine(XPADDR(pmd)).maddr; + + return (pmd_t){ pmd }; +} + +pgd_t xen_make_pgd(unsigned long long pgd) +{ + if (pgd & _PAGE_PRESENT) + pgd = phys_to_machine(XPADDR(pgd)).maddr; + + return (pgd_t){ pgd }; +} +#else /* !PAE */ +void xen_set_pte(pte_t *ptep, pte_t pte) +{ + *ptep = pte; +} + +unsigned long xen_pte_val(pte_t pte) +{ + unsigned long ret = pte.pte_low; + + if (ret & _PAGE_PRESENT) + ret = machine_to_phys(XMADDR(ret)).paddr; + + return ret; +} + +unsigned long xen_pgd_val(pgd_t pgd) +{ + unsigned long ret = pgd.pgd; + if (ret) + ret = machine_to_phys(XMADDR(ret)).paddr | 1; + return ret; +} + +pte_t xen_make_pte(unsigned long pte) +{ + if (pte & _PAGE_PRESENT) + pte = phys_to_machine(XPADDR(pte)).maddr; + + return (pte_t){ pte }; +} + +pgd_t xen_make_pgd(unsigned long pgd) +{ + if (pgd & _PAGE_PRESENT) + pgd = phys_to_machine(XPADDR(pgd)).maddr; + + return (pgd_t){ pgd }; +} +#endif /* CONFIG_X86_PAE */ + + + +/* + (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 *, unsigned), + 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), 0); + + 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), 0); + + 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), 0); + } + } + } + + flush |= (*func)(virt_to_page(pgd_base), UVMF_TLB_FLUSH); + + return flush; +} + +static int pin_page(struct page *page, unsigned flags) +{ + unsigned pgfl = test_and_set_bit(PG_pinned, &page->flags); + 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); + + flush = 0; + + MULTI_update_va_mapping(mcs.mc, (unsigned long)pt, + pfn_pte(pfn, PAGE_KERNEL_RO), + flags); + } + + 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) +{ + struct multicall_space mcs; + struct mmuext_op *op; + + 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(); + } + + mcs = __xen_mc_entry(sizeof(*op)); + op = mcs.args; + +#ifdef CONFIG_X86_PAE + op->cmd = MMUEXT_PIN_L3_TABLE; +#else + op->cmd = MMUEXT_PIN_L2_TABLE; +#endif + op->arg1.mfn = pfn_to_mfn(PFN_DOWN(__pa(pgd))); + MULTI_mmuext_op(mcs.mc, op, 1, NULL, DOMID_SELF); + + 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, unsigned flags) +{ + 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, unsigned flags) +{ + unsigned pgfl = test_and_clear_bit(PG_pinned, &page->flags); + + if (pgfl && !PageHighMem(page)) { + void *pt = lowmem_page_address(page); + unsigned long pfn = page_to_pfn(page); + struct multicall_space mcs = __xen_mc_entry(0); + + MULTI_update_va_mapping(mcs.mc, (unsigned long)pt, + pfn_pte(pfn, PAGE_KERNEL), + flags); + } + + return 0; /* never need to flush on unpin */ +} + +/* Release a pagetables pages back as normal RW */ +static void xen_pgd_unpin(pgd_t *pgd) +{ + struct mmuext_op *op; + struct multicall_space mcs; + + xen_mc_batch(); + + mcs = __xen_mc_entry(sizeof(*op)); + + op = mcs.args; + op->cmd = MMUEXT_UNPIN_TABLE; + op->arg1.mfn = pfn_to_mfn(PFN_DOWN(__pa(pgd))); + + MULTI_mmuext_op(mcs.mc, op, 1, NULL, DOMID_SELF); + + 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()); +} + +static void drop_mm_ref(struct mm_struct *mm) +{ + if (current->active_mm == mm) { + if (current->mm == mm) + load_cr3(swapper_pg_dir); + else + leave_mm(smp_processor_id()); + } + + if (!cpus_empty(mm->cpu_vm_mask)) + xen_smp_call_function_mask(mm->cpu_vm_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); +} -- cgit v1.2.3