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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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