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    SubjectRe: [PATCH v4 07/24] xen/arm: Xen detection and shared_info page mapping
    On Fri, 14 Sep 2012, Konrad Rzeszutek Wilk wrote:
    > On Fri, Sep 14, 2012 at 12:13:09PM +0100, Stefano Stabellini wrote:
    > > Check for a node in the device tree compatible with "xen,xen", if it is
    > > present set xen_domain_type to XEN_HVM_DOMAIN and continue
    > > initialization.
    > >
    > > Map the real shared info page using XENMEM_add_to_physmap with
    > > XENMAPSPACE_shared_info.
    > >
    > > Changes in v4:
    > >
    > > - simpler parsing of Xen version in the compatible DT node.
    > >
    > > Changes in v3:
    > >
    > > - use the "xen,xen" notation rather than "arm,xen";
    > > - add an additional check on the presence of the Xen version.
    > >
    > > Changes in v2:
    > >
    > > - replace pr_info with pr_debug.
    > >
    > > Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
    > > ---
    > > arch/arm/xen/enlighten.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++
    > > 1 files changed, 61 insertions(+), 0 deletions(-)
    > >
    > > diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
    > > index c535540..6a0217d 100644
    > > --- a/arch/arm/xen/enlighten.c
    > > +++ b/arch/arm/xen/enlighten.c
    > > @@ -5,6 +5,9 @@
    > > #include <asm/xen/hypervisor.h>
    > > #include <asm/xen/hypercall.h>
    > > #include <linux/module.h>
    > > +#include <linux/of.h>
    > > +#include <linux/of_irq.h>
    > > +#include <linux/of_address.h>
    > >
    > > struct start_info _xen_start_info;
    > > struct start_info *xen_start_info = &_xen_start_info;
    > > @@ -33,3 +36,61 @@ int xen_remap_domain_mfn_range(struct vm_area_struct *vma,
    > > return -ENOSYS;
    > > }
    > > EXPORT_SYMBOL_GPL(xen_remap_domain_mfn_range);
    > > +
    > > +/*
    > > + * see Documentation/devicetree/bindings/arm/xen.txt for the
    > > + * documentation of the Xen Device Tree format.
    > > + */
    > > +static int __init xen_guest_init(void)
    > > +{
    > > + struct xen_add_to_physmap xatp;
    > > + static struct shared_info *shared_info_page = 0;
    > > + struct device_node *node;
    > > + int len;
    > > + const char *s = NULL;
    > > + const char *version = NULL;
    > > + const char *xen_prefix = "xen,xen-";
    > > +
    > > + node = of_find_compatible_node(NULL, NULL, "xen,xen");
    > > + if (!node) {
    > > + pr_debug("No Xen support\n");
    > > + return 0;
    > > + }
    > > + s = of_get_property(node, "compatible", &len);
    > > + if (strlen(xen_prefix) + 3 < len &&
    > > + !strncmp(xen_prefix, s, strlen(xen_prefix)))
    >
    > If we have version '4.3.1' won't this trip us over?

    This isn't an issue:

    if (8 + 3 < 14 &&
    !strncmp("xen,xen-", "xen,xen-4.3.1", 8)

    would return true

    and version is set to "4.3.1".


    > Or if we only have 'major' and 'minor', then won't '4.11' trip us
    > over too?

    For the same reason this shouldn't be an issue either:

    if (8 + 3 < 13 &&
    !strncmp("xen,xen-", "xen,xen-4.11", 8)

    would return true

    and version would be set to "4.11".

    BTW I have just tried both out of paranoia and it works as expected.


    > > + version = s + strlen(xen_prefix);
    > > + if (version == NULL) {
    > > + pr_debug("Xen version not found\n");
    > > + return 0;
    > > + }
    > > + xen_domain_type = XEN_HVM_DOMAIN;
    > > +
    > > + if (!shared_info_page)
    > > + shared_info_page = (struct shared_info *)
    > > + get_zeroed_page(GFP_KERNEL);
    > > + if (!shared_info_page) {
    > > + pr_err("not enough memory\n");
    > > + return -ENOMEM;
    > > + }
    > > + xatp.domid = DOMID_SELF;
    > > + xatp.idx = 0;
    > > + xatp.space = XENMAPSPACE_shared_info;
    > > + xatp.gpfn = __pa(shared_info_page) >> PAGE_SHIFT;
    > > + if (HYPERVISOR_memory_op(XENMEM_add_to_physmap, &xatp))
    > > + BUG();
    > > +
    > > + HYPERVISOR_shared_info = (struct shared_info *)shared_info_page;
    > > +
    > > + /* xen_vcpu is a pointer to the vcpu_info struct in the shared_info
    > > + * page, we use it in the event channel upcall and in some pvclock
    > > + * related functions. We don't need the vcpu_info placement
    > > + * optimizations because we don't use any pv_mmu or pv_irq op on
    > > + * HVM.
    > > + * The shared info contains exactly 1 CPU (the boot CPU). The guest
    > > + * is required to use VCPUOP_register_vcpu_info to place vcpu info
    > > + * for secondary CPUs as they are brought up. */
    > > + per_cpu(xen_vcpu, 0) = &HYPERVISOR_shared_info->vcpu_info[0];
    > > + return 0;
    > > +}
    > > +core_initcall(xen_guest_init);
    > > --
    > > 1.7.2.5
    >


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