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    Subject[PATCH 06/24] xen: make xen_load_gdt simpler
    Date
    From: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

    Remove use of multicall machinery which is unused (gdt loading
    is never performance critical). This removes the implicit use
    of percpu variables, which simplifies understanding how
    the percpu code's use of load_gdt interacts with this code.

    Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
    ---
    arch/x86/xen/enlighten.c | 14 ++++++--------
    1 files changed, 6 insertions(+), 8 deletions(-)

    diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
    index 5776dc2..48b399b 100644
    --- a/arch/x86/xen/enlighten.c
    +++ b/arch/x86/xen/enlighten.c
    @@ -284,12 +284,11 @@ static void xen_set_ldt(const void *addr, unsigned entries)

    static void xen_load_gdt(const struct desc_ptr *dtr)
    {
    - unsigned long *frames;
    unsigned long va = dtr->address;
    unsigned int size = dtr->size + 1;
    unsigned pages = (size + PAGE_SIZE - 1) / PAGE_SIZE;
    + unsigned long frames[pages];
    int f;
    - struct multicall_space mcs;

    /* A GDT can be up to 64k in size, which corresponds to 8192
    8-byte entries, or 16 4k pages.. */
    @@ -297,9 +296,6 @@ static void xen_load_gdt(const struct desc_ptr *dtr)
    BUG_ON(size > 65536);
    BUG_ON(va & ~PAGE_MASK);

    - mcs = xen_mc_entry(sizeof(*frames) * pages);
    - frames = mcs.args;
    -
    for (f = 0; va < dtr->address + size; va += PAGE_SIZE, f++) {
    int level;
    pte_t *ptep = lookup_address(va, &level);
    @@ -314,13 +310,15 @@ static void xen_load_gdt(const struct desc_ptr *dtr)

    frames[f] = mfn;

    + printk("xen_load_gdt: %d va=%p mfn=%lx pfn=%lx va'=%p\n",
    + f, (void *)va, mfn, pfn, virt);
    +
    make_lowmem_page_readonly((void *)va);
    make_lowmem_page_readonly(virt);
    }

    - MULTI_set_gdt(mcs.mc, frames, size / sizeof(struct desc_struct));
    -
    - xen_mc_issue(PARAVIRT_LAZY_CPU);
    + if (HYPERVISOR_set_gdt(frames, size / sizeof(struct desc_struct)))
    + BUG();
    }

    static void load_TLS_descriptor(struct thread_struct *t,
    --
    1.6.0.6


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