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    SubjectRe: [PATCH 4/7] xen/hvm: Xen PV extension of HVM initialization
    On 03/04/2010 01:36 AM, Sheng Yang wrote:
    > diff --git a/arch/x86/xen/Kconfig b/arch/x86/xen/Kconfig
    > index b83e119..af3c7a0 100644
    > --- a/arch/x86/xen/Kconfig
    > +++ b/arch/x86/xen/Kconfig
    > @@ -36,3 +36,11 @@ config XEN_DEBUG_FS
    > help
    > Enable statistics output and various tuning options in debugfs.
    > Enabling this option may incur a significant performance overhead.
    > +
    > +config XEN_HVM_PV
    > + bool "PV extension of HVM"
    > + depends on XEN&& X86_64
    > + default n
    > + help
    > + Enable the PV extension of HVM, so that HVM guest would benefit from
    > + PV features like PV timer and evtchn.
    >

    Unless there's a strong reason to make this a user-visible setting, I'd
    make it a hidden option which is enabled by default when the
    dependencies are correct.

    > diff --git a/arch/x86/xen/Makefile b/arch/x86/xen/Makefile
    > index 3bb4fc2..73bd5db 100644
    > --- a/arch/x86/xen/Makefile
    > +++ b/arch/x86/xen/Makefile
    > @@ -17,4 +17,5 @@ obj-y := enlighten.o setup.o multicalls.o mmu.o irq.o \
    > obj-$(CONFIG_SMP) += smp.o
    > obj-$(CONFIG_PARAVIRT_SPINLOCKS)+= spinlock.o
    > obj-$(CONFIG_XEN_DEBUG_FS) += debugfs.o
    > +obj-$(CONFIG_XEN_HVM_PV) += hvmpv.o
    >
    > diff --git a/arch/x86/xen/hvmpv.c b/arch/x86/xen/hvmpv.c
    > new file mode 100644
    > index 0000000..7a741ed
    > --- /dev/null
    > +++ b/arch/x86/xen/hvmpv.c
    > @@ -0,0 +1,133 @@
    > +/*
    > + * PV extension of HVM implementation.
    > + *
    > + * Sheng Yang<sheng@linux.intel.com>, Intel Corporation, 2010
    > + *
    > + */
    > +#include<linux/kernel.h>
    > +#include<linux/init.h>
    > +#include<linux/percpu.h>
    > +#include<linux/module.h>
    > +
    > +#include<xen/xen.h>
    > +#include<xen/features.h>
    > +#include<xen/events.h>
    > +#include<xen/hvm.h>
    > +#include<xen/interface/xen.h>
    > +#include<xen/interface/version.h>
    > +#include<xen/interface/memory.h>
    > +
    > +#include<asm/xen/cpuid.h>
    > +#include<asm/xen/hypercall.h>
    > +#include<asm/xen/hypervisor.h>
    > +
    > +#include "xen-ops.h"
    > +
    > +u32 xen_hvm_pv_features;
    > +EXPORT_SYMBOL_GPL(xen_hvm_pv_features);
    > +
    > +static const struct pv_info xen_hvm_pv_info __initdata = {
    > + .paravirt_enabled = 1,
    > + .shared_kernel_pmd = 0,
    > + .kernel_rpl = 0,
    > + .name = "Xen",
    > +};
    > +
    > +static void __init xen_hvm_pv_banner(void)
    > +{
    > + unsigned version = HYPERVISOR_xen_version(XENVER_version, NULL);
    > + struct xen_extraversion extra;
    > + HYPERVISOR_xen_version(XENVER_extraversion,&extra);
    > +
    > + printk(KERN_INFO "Booting PV extended HVM kernel on %s\n",
    > + pv_info.name);
    > + printk(KERN_INFO "Xen version: %d.%d%s\n",
    > + version>> 16, version& 0xffff, extra.extraversion);
    > +}
    > +
    > +static int __init xen_para_available(void)
    > +{
    > + uint32_t eax, ebx, ecx, edx;
    > + cpuid(XEN_CPUID_LEAF(0),&eax,&ebx,&ecx,&edx);
    > +
    > + if (ebx == XEN_CPUID_SIGNATURE_EBX&&
    > + ecx == XEN_CPUID_SIGNATURE_ECX&&
    > + edx == XEN_CPUID_SIGNATURE_EDX&&
    > + ((eax - XEN_CPUID_LEAF(0))>= 2))
    > + return 1;
    > +
    > + return 0;
    > +}
    > +
    > +static int __init enable_hvm_pv(u64 flags)
    > +{
    > + struct xen_hvm_pv_type a;
    > +
    > + a.domid = DOMID_SELF;
    > + a.flags = flags;
    > + return HYPERVISOR_hvm_op(HVMOP_enable_pv,&a);
    > +}
    > +
    > +static int __init init_hvm_pv_info(void)
    > +{
    > + uint32_t ecx, edx, pages, msr;
    > + u64 pfn;
    > +
    > + if (!xen_para_available())
    > + return -EINVAL;
    > +
    > + cpuid(XEN_CPUID_LEAF(2),&pages,&msr,&ecx,&edx);
    > +
    > + /* Check if hvm_pv mode is supported */
    > + if (!(edx& XEN_CPUID_FEAT2_HVM_PV))
    > + return -ENODEV;
    > +
    > + /* We only support 1 page of hypercall for now */
    > + if (pages != 1)
    > + return -ENOMEM;
    >

    Why does it matter? If you're only using hypercalls in the first page,
    it doesn't matter whether Xen exports more pages beyond that.

    > +
    > + pfn = __pa(hypercall_page);
    > + wrmsrl(msr, pfn);
    >
    wrmsr_safe() with error check, just in case it fails?

    > +
    > + xen_setup_features();
    > +
    > + x86_init.oem.banner = xen_hvm_pv_banner;
    > + pv_info = xen_hvm_pv_info;
    > +
    > + xen_domain_type = XEN_HVM_DOMAIN;
    >

    Set this very last, once everything else has successfully set up.

    > +
    > + return 0;
    > +}
    > +
    > +static struct shared_info shared_info_page __page_aligned_bss;
    > +
    > +static void __init init_shared_info(void)
    > +{
    > + struct xen_add_to_physmap xatp;
    > +
    > + 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();
    >
    It isn't too late to back out if it fails; just return an error code.
    > +
    > + HYPERVISOR_shared_info = (struct shared_info *)&shared_info_page;
    > +
    > + per_cpu(xen_vcpu, 0) =&HYPERVISOR_shared_info->vcpu_info[0];
    > +}
    > +
    > +void __init xen_guest_init(void)
    > +{
    > + int r;
    > +
    > + /* Ensure the we won't confused with others */
    > + if (xen_domain_type != XEN_NATIVE)
    >
    Just use xen_domain()?

    > + return;
    > +
    > + r = init_hvm_pv_info();
    > + if (r< 0)
    > + return;
    > +
    > + init_shared_info();
    > +}
    > diff --git a/include/xen/interface/hvm/hvm_op.h b/include/xen/interface/hvm/hvm_op.h
    > index 7c74ba4..3f0b118 100644
    > --- a/include/xen/interface/hvm/hvm_op.h
    > +++ b/include/xen/interface/hvm/hvm_op.h
    > @@ -69,4 +69,12 @@ DEFINE_GUEST_HANDLE_STRUCT(xen_hvm_set_pci_link_route);
    > /* Flushes all VCPU TLBs: @arg must be NULL. */
    > #define HVMOP_flush_tlbs 5
    >
    > +#define HVMOP_enable_pv 9
    > +struct xen_hvm_pv_type {
    > + domid_t domid;
    > + uint32_t flags;
    > +#define HVM_PV_CLOCK (1ull<<0)
    > +#define HVM_PV_EVTCHN (1ull<<1)
    > +};
    > +
    > #endif /* __XEN_PUBLIC_HVM_HVM_OP_H__ */
    > diff --git a/include/xen/xen.h b/include/xen/xen.h
    > index a164024..11f5ced 100644
    > --- a/include/xen/xen.h
    > +++ b/include/xen/xen.h
    > @@ -19,6 +19,15 @@ extern enum xen_domain_type xen_domain_type;
    > #define xen_hvm_domain() (xen_domain()&& \
    > xen_domain_type == XEN_HVM_DOMAIN)
    >
    > +#ifdef CONFIG_XEN_HVM_PV
    > +
    > +#define XEN_HVM_PV_EVTCHN_ENABLED (1u<< 1)
    > +extern u32 xen_hvm_pv_features;
    > +
    > +#define xen_hvm_pv_evtchn_enabled() \
    > + (xen_hvm_pv_features& XEN_HVM_PV_EVTCHN_ENABLED)
    > +#endif /* CONFIG_XEN_HVM_PV */
    >

    Did you compile test this with !CONFIG_XEN_HVM_PV? I think it would
    fail with xen_hvm_pv_evtchn_enabled() undefined. Fortunately making
    xen_hvm_pv_evtchn_enabled() evaluate to constant 0 in the !configed case
    will clean things up.

    J


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