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    Subject[PATCH 38/41] KVM: Simply gfn_to_page()
    Date
    Mapping a guest page to a host page is a common operation.  Currently,
    one has first to find the memory slot where the page belongs (gfn_to_memslot),
    then locate the page itself (gfn_to_page()).

    This is clumsy, and also won't work well with memory aliases. So simplify
    gfn_to_page() not to require memory slot translation first, and instead do it
    internally.

    Signed-off-by: Avi Kivity <avi@qumranet.com>
    ---
    drivers/kvm/kvm.h | 12 +-----------
    drivers/kvm/kvm_main.c | 45 +++++++++++++++++++++++++--------------------
    drivers/kvm/mmu.c | 12 ++++--------
    drivers/kvm/vmx.c | 6 +++---
    4 files changed, 33 insertions(+), 42 deletions(-)

    diff --git a/drivers/kvm/kvm.h b/drivers/kvm/kvm.h
    index 59357be..d19985a 100644
    --- a/drivers/kvm/kvm.h
    +++ b/drivers/kvm/kvm.h
    @@ -443,11 +443,7 @@ void kvm_emulator_want_group7_invlpg(void);

    extern hpa_t bad_page_address;

    -static inline struct page *gfn_to_page(struct kvm_memory_slot *slot, gfn_t gfn)
    -{
    - return slot->phys_mem[gfn - slot->base_gfn];
    -}
    -
    +struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn);
    struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn);
    void mark_page_dirty(struct kvm *kvm, gfn_t gfn);

    @@ -523,12 +519,6 @@ static inline int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t gva,
    return vcpu->mmu.page_fault(vcpu, gva, error_code);
    }

    -static inline struct page *_gfn_to_page(struct kvm *kvm, gfn_t gfn)
    -{
    - struct kvm_memory_slot *slot = gfn_to_memslot(kvm, gfn);
    - return (slot) ? slot->phys_mem[gfn - slot->base_gfn] : NULL;
    -}
    -
    static inline int is_long_mode(struct kvm_vcpu *vcpu)
    {
    #ifdef CONFIG_X86_64
    diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
    index 1ef5e9a..aaaf306 100644
    --- a/drivers/kvm/kvm_main.c
    +++ b/drivers/kvm/kvm_main.c
    @@ -420,12 +420,12 @@ static int load_pdptrs(struct kvm_vcpu *vcpu, unsigned long cr3)
    u64 pdpte;
    u64 *pdpt;
    int ret;
    - struct kvm_memory_slot *memslot;
    + struct page *page;

    spin_lock(&vcpu->kvm->lock);
    - memslot = gfn_to_memslot(vcpu->kvm, pdpt_gfn);
    - /* FIXME: !memslot - emulate? 0xff? */
    - pdpt = kmap_atomic(gfn_to_page(memslot, pdpt_gfn), KM_USER0);
    + page = gfn_to_page(vcpu->kvm, pdpt_gfn);
    + /* FIXME: !page - emulate? 0xff? */
    + pdpt = kmap_atomic(page, KM_USER0);

    ret = 1;
    for (i = 0; i < 4; ++i) {
    @@ -861,6 +861,17 @@ struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn)
    }
    EXPORT_SYMBOL_GPL(gfn_to_memslot);

    +struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn)
    +{
    + struct kvm_memory_slot *slot;
    +
    + slot = gfn_to_memslot(kvm, gfn);
    + if (!slot)
    + return NULL;
    + return slot->phys_mem[gfn - slot->base_gfn];
    +}
    +EXPORT_SYMBOL_GPL(gfn_to_page);
    +
    void mark_page_dirty(struct kvm *kvm, gfn_t gfn)
    {
    int i;
    @@ -899,20 +910,20 @@ static int emulator_read_std(unsigned long addr,
    unsigned offset = addr & (PAGE_SIZE-1);
    unsigned tocopy = min(bytes, (unsigned)PAGE_SIZE - offset);
    unsigned long pfn;
    - struct kvm_memory_slot *memslot;
    - void *page;
    + struct page *page;
    + void *page_virt;

    if (gpa == UNMAPPED_GVA)
    return X86EMUL_PROPAGATE_FAULT;
    pfn = gpa >> PAGE_SHIFT;
    - memslot = gfn_to_memslot(vcpu->kvm, pfn);
    - if (!memslot)
    + page = gfn_to_page(vcpu->kvm, pfn);
    + if (!page)
    return X86EMUL_UNHANDLEABLE;
    - page = kmap_atomic(gfn_to_page(memslot, pfn), KM_USER0);
    + page_virt = kmap_atomic(page, KM_USER0);

    - memcpy(data, page + offset, tocopy);
    + memcpy(data, page_virt + offset, tocopy);

    - kunmap_atomic(page, KM_USER0);
    + kunmap_atomic(page_virt, KM_USER0);

    bytes -= tocopy;
    data += tocopy;
    @@ -963,16 +974,14 @@ static int emulator_read_emulated(unsigned long addr,
    static int emulator_write_phys(struct kvm_vcpu *vcpu, gpa_t gpa,
    unsigned long val, int bytes)
    {
    - struct kvm_memory_slot *m;
    struct page *page;
    void *virt;

    if (((gpa + bytes - 1) >> PAGE_SHIFT) != (gpa >> PAGE_SHIFT))
    return 0;
    - m = gfn_to_memslot(vcpu->kvm, gpa >> PAGE_SHIFT);
    - if (!m)
    + page = gfn_to_page(vcpu->kvm, gpa >> PAGE_SHIFT);
    + if (!page)
    return 0;
    - page = gfn_to_page(m, gpa >> PAGE_SHIFT);
    kvm_mmu_pre_write(vcpu, gpa, bytes);
    mark_page_dirty(vcpu->kvm, gpa >> PAGE_SHIFT);
    virt = kmap_atomic(page, KM_USER0);
    @@ -2507,15 +2516,11 @@ static struct page *kvm_vm_nopage(struct vm_area_struct *vma,
    {
    struct kvm *kvm = vma->vm_file->private_data;
    unsigned long pgoff;
    - struct kvm_memory_slot *slot;
    struct page *page;

    *type = VM_FAULT_MINOR;
    pgoff = ((address - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
    - slot = gfn_to_memslot(kvm, pgoff);
    - if (!slot)
    - return NOPAGE_SIGBUS;
    - page = gfn_to_page(slot, pgoff);
    + page = gfn_to_page(kvm, pgoff);
    if (!page)
    return NOPAGE_SIGBUS;
    get_page(page);
    diff --git a/drivers/kvm/mmu.c b/drivers/kvm/mmu.c
    index 707f63c..35135ec 100644
    --- a/drivers/kvm/mmu.c
    +++ b/drivers/kvm/mmu.c
    @@ -390,13 +390,11 @@ static void rmap_write_protect(struct kvm_vcpu *vcpu, u64 gfn)
    {
    struct kvm *kvm = vcpu->kvm;
    struct page *page;
    - struct kvm_memory_slot *slot;
    struct kvm_rmap_desc *desc;
    u64 *spte;

    - slot = gfn_to_memslot(kvm, gfn);
    - BUG_ON(!slot);
    - page = gfn_to_page(slot, gfn);
    + page = gfn_to_page(kvm, gfn);
    + BUG_ON(!page);

    while (page_private(page)) {
    if (!(page_private(page) & 1))
    @@ -711,14 +709,12 @@ hpa_t safe_gpa_to_hpa(struct kvm_vcpu *vcpu, gpa_t gpa)

    hpa_t gpa_to_hpa(struct kvm_vcpu *vcpu, gpa_t gpa)
    {
    - struct kvm_memory_slot *slot;
    struct page *page;

    ASSERT((gpa & HPA_ERR_MASK) == 0);
    - slot = gfn_to_memslot(vcpu->kvm, gpa >> PAGE_SHIFT);
    - if (!slot)
    + page = gfn_to_page(vcpu->kvm, gpa >> PAGE_SHIFT);
    + if (!page)
    return gpa | HPA_ERR_MASK;
    - page = gfn_to_page(slot, gpa >> PAGE_SHIFT);
    return ((hpa_t)page_to_pfn(page) << PAGE_SHIFT)
    | (gpa & (PAGE_SIZE-1));
    }
    diff --git a/drivers/kvm/vmx.c b/drivers/kvm/vmx.c
    index b64b7b7..61a6116 100644
    --- a/drivers/kvm/vmx.c
    +++ b/drivers/kvm/vmx.c
    @@ -926,9 +926,9 @@ static int init_rmode_tss(struct kvm* kvm)
    gfn_t fn = rmode_tss_base(kvm) >> PAGE_SHIFT;
    char *page;

    - p1 = _gfn_to_page(kvm, fn++);
    - p2 = _gfn_to_page(kvm, fn++);
    - p3 = _gfn_to_page(kvm, fn);
    + p1 = gfn_to_page(kvm, fn++);
    + p2 = gfn_to_page(kvm, fn++);
    + p3 = gfn_to_page(kvm, fn);

    if (!p1 || !p2 || !p3) {
    kvm_printf(kvm,"%s: gfn_to_page failed\n", __FUNCTION__);
    --
    1.5.0.5
    -
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