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    Subject[PATCH 08/19] xen/dom0: use _PAGE_IOMAP in ioremap to do machine mappings
    Date
    In a Xen domain, ioremap operates on machine addresses, not
    pseudo-physical addresses. We use _PAGE_IOMAP to determine whether a
    mapping is intended for machine addresses.

    Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
    ---
    arch/x86/include/asm/xen/page.h | 8 +---
    arch/x86/xen/enlighten.c | 4 ++-
    arch/x86/xen/mmu.c | 70 +++++++++++++++++++++++++++++++++++++-
    3 files changed, 73 insertions(+), 9 deletions(-)
    diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
    index 4bd990e..20c3872 100644
    --- a/arch/x86/include/asm/xen/page.h
    +++ b/arch/x86/include/asm/xen/page.h
    @@ -112,13 +112,9 @@ static inline xpaddr_t machine_to_phys(xmaddr_t machine)
    */
    static inline unsigned long mfn_to_local_pfn(unsigned long mfn)
    {
    - extern unsigned long max_mapnr;
    unsigned long pfn = mfn_to_pfn(mfn);
    - if ((pfn < max_mapnr)
    - && !xen_feature(XENFEAT_auto_translated_physmap)
    - && (get_phys_to_machine(pfn) != mfn))
    - return max_mapnr; /* force !pfn_valid() */
    - /* XXX fixme; not true with sparsemem */
    + if (get_phys_to_machine(pfn) != mfn)
    + return -1; /* force !pfn_valid() */
    return pfn;
    }

    diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
    index 1b89d1c..c12a3c8 100644
    --- a/arch/x86/xen/enlighten.c
    +++ b/arch/x86/xen/enlighten.c
    @@ -938,7 +938,9 @@ asmlinkage void __init xen_start_kernel(void)

    /* Prevent unwanted bits from being set in PTEs. */
    __supported_pte_mask &= ~_PAGE_GLOBAL;
    - if (!xen_initial_domain())
    + if (xen_initial_domain())
    + __supported_pte_mask |= _PAGE_IOMAP;
    + else
    __supported_pte_mask &= ~(_PAGE_PWT | _PAGE_PCD);

    /* Don't do the full vcpu_info placement stuff until we have a
    diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
    index 36125ea..6aa6d55 100644
    --- a/arch/x86/xen/mmu.c
    +++ b/arch/x86/xen/mmu.c
    @@ -336,6 +336,28 @@ static bool xen_page_pinned(void *ptr)
    return PagePinned(page);
    }

    +static bool xen_iomap_pte(pte_t pte)
    +{
    + return xen_initial_domain() && (pte_flags(pte) & _PAGE_IOMAP);
    +}
    +
    +static void xen_set_iomap_pte(pte_t *ptep, pte_t pteval)
    +{
    + struct multicall_space mcs;
    + struct mmu_update *u;
    +
    + mcs = xen_mc_entry(sizeof(*u));
    + u = mcs.args;
    +
    + /* ptep might be kmapped when using 32-bit HIGHPTE */
    + u->ptr = arbitrary_virt_to_machine(ptep).maddr;
    + u->val = pte_val_ma(pteval);
    +
    + MULTI_mmu_update(mcs.mc, mcs.args, 1, NULL, DOMID_IO);
    +
    + xen_mc_issue(PARAVIRT_LAZY_MMU);
    +}
    +
    static void xen_extend_mmu_update(const struct mmu_update *update)
    {
    struct multicall_space mcs;
    @@ -416,6 +438,11 @@ void xen_set_pte_at(struct mm_struct *mm, unsigned long addr,
    if (mm == &init_mm)
    preempt_disable();

    + if (xen_iomap_pte(pteval)) {
    + xen_set_iomap_pte(ptep, pteval);
    + goto out;
    + }
    +
    ADD_STATS(set_pte_at, 1);
    // ADD_STATS(set_pte_at_pinned, xen_page_pinned(ptep));
    ADD_STATS(set_pte_at_current, mm == current->mm);
    @@ -488,8 +515,25 @@ static pteval_t pte_pfn_to_mfn(pteval_t val)
    return val;
    }

    +static pteval_t iomap_pte(pteval_t val)
    +{
    + if (val & _PAGE_PRESENT) {
    + unsigned long pfn = (val & PTE_PFN_MASK) >> PAGE_SHIFT;
    + pteval_t flags = val & PTE_FLAGS_MASK;
    +
    + /* We assume the pte frame number is a MFN, so
    + just use it as-is. */
    + val = ((pteval_t)pfn << PAGE_SHIFT) | flags;
    + }
    +
    + return val;
    +}
    +
    pteval_t xen_pte_val(pte_t pte)
    {
    + if (xen_initial_domain() && (pte.pte & _PAGE_IOMAP))
    + return pte.pte;
    +
    return pte_mfn_to_pfn(pte.pte);
    }
    PV_CALLEE_SAVE_REGS_THUNK(xen_pte_val);
    @@ -502,7 +546,11 @@ PV_CALLEE_SAVE_REGS_THUNK(xen_pgd_val);

    pte_t xen_make_pte(pteval_t pte)
    {
    - pte = pte_pfn_to_mfn(pte);
    + if (unlikely(xen_initial_domain() && (pte & _PAGE_IOMAP)))
    + pte = iomap_pte(pte);
    + else
    + pte = pte_pfn_to_mfn(pte);
    +
    return native_make_pte(pte);
    }
    PV_CALLEE_SAVE_REGS_THUNK(xen_make_pte);
    @@ -558,6 +606,11 @@ void xen_set_pud(pud_t *ptr, pud_t val)

    void xen_set_pte(pte_t *ptep, pte_t pte)
    {
    + if (xen_iomap_pte(pte)) {
    + xen_set_iomap_pte(ptep, pte);
    + return;
    + }
    +
    ADD_STATS(pte_update, 1);
    // ADD_STATS(pte_update_pinned, xen_page_pinned(ptep));
    ADD_STATS(pte_update_batched, paravirt_get_lazy_mode() == PARAVIRT_LAZY_MMU);
    @@ -574,6 +627,11 @@ void xen_set_pte(pte_t *ptep, pte_t pte)
    #ifdef CONFIG_X86_PAE
    void xen_set_pte_atomic(pte_t *ptep, pte_t pte)
    {
    + if (xen_iomap_pte(pte)) {
    + xen_set_iomap_pte(ptep, pte);
    + return;
    + }
    +
    set_64bit((u64 *)ptep, native_pte_val(pte));
    }

    @@ -1770,12 +1828,20 @@ static void xen_set_fixmap(unsigned idx, unsigned long phys, pgprot_t prot)
    #ifdef CONFIG_X86_LOCAL_APIC
    case FIX_APIC_BASE: /* maps dummy local APIC */
    #endif
    + /* All local page mappings */
    pte = pfn_pte(phys, prot);
    break;

    - default:
    + case FIX_PARAVIRT_BOOTMAP:
    + /* This is an MFN, but it isn't an IO mapping from the
    + IO domain */
    pte = mfn_pte(phys, prot);
    break;
    +
    + default:
    + /* By default, set_fixmap is used for hardware mappings */
    + pte = mfn_pte(phys, __pgprot(pgprot_val(prot) | _PAGE_IOMAP));
    + break;
    }

    __native_set_fixmap(idx, pte);
    --
    1.6.0.6


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