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[Xen-devel] Re: [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@xxxxxxxxxxxxxxx>, 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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