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    SubjectRe: [Xen-devel] [PATCH 3/7] xen/hvm: Xen PV extension of HVM initialization
    On 03/01/2010 01:38 AM, Sheng Yang wrote:
    > The PV extension of HVM(once known as Hybrid) is started from real mode like
    > HVM guest, but also with a component based PV feature selection(e.g. PV halt,
    > PV timer, event channel, then PV drivers). So guest can takes the advantages
    > of both H/W virtualization and Para-Virtualization.
    >
    > This patch introduced the PV extension of HVM guest initialization.
    >
    > Guest would detect the capability using CPUID 0x40000002.edx, then call
    > HVMOP_enable_pv hypercall to enable pv support in hypervisor.
    >
    > Signed-off-by: Sheng Yang<sheng@linux.intel.com>
    > Signed-off-by: Yaozu (Eddie) Dong<eddie.dong@intel.com>
    > ---
    > arch/x86/include/asm/xen/cpuid.h | 5 ++
    > arch/x86/xen/enlighten.c | 115 ++++++++++++++++++++++++++++++++++++
    > arch/x86/xen/irq.c | 21 +++++++
    > arch/x86/xen/xen-head.S | 6 ++
    > arch/x86/xen/xen-ops.h | 1 +
    > include/xen/interface/hvm/hvm_op.h | 7 ++
    > include/xen/xen.h | 9 +++
    > 7 files changed, 164 insertions(+), 0 deletions(-)
    >
    > diff --git a/arch/x86/include/asm/xen/cpuid.h b/arch/x86/include/asm/xen/cpuid.h
    > index 8787f03..a93c851 100644
    > --- a/arch/x86/include/asm/xen/cpuid.h
    > +++ b/arch/x86/include/asm/xen/cpuid.h
    > @@ -65,4 +65,9 @@
    > #define _XEN_CPUID_FEAT1_MMU_PT_UPDATE_PRESERVE_AD 0
    > #define XEN_CPUID_FEAT1_MMU_PT_UPDATE_PRESERVE_AD (1u<<0)
    >
    > +#define _XEN_CPUID_FEAT2_HVM_PV 0
    > +#define XEN_CPUID_FEAT2_HVM_PV (1u<<0)
    > +#define _XEN_CPUID_FEAT2_HVM_PV_EVTCHN 1
    > +#define XEN_CPUID_FEAT2_HVM_PV_EVTCHN (1u<<1)
    > +
    > #endif /* __XEN_PUBLIC_ARCH_X86_CPUID_H__ */
    > diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
    > index 36daccb..fdb9664 100644
    > --- a/arch/x86/xen/enlighten.c
    > +++ b/arch/x86/xen/enlighten.c
    > @@ -34,6 +34,8 @@
    > #include<xen/interface/version.h>
    > #include<xen/interface/physdev.h>
    > #include<xen/interface/vcpu.h>
    > +#include<xen/interface/memory.h>
    > +#include<xen/interface/hvm/hvm_op.h>
    > #include<xen/features.h>
    > #include<xen/page.h>
    > #include<xen/hvc-console.h>
    > @@ -43,6 +45,7 @@
    > #include<asm/page.h>
    > #include<asm/xen/hypercall.h>
    > #include<asm/xen/hypervisor.h>
    > +#include<asm/xen/cpuid.h>
    > #include<asm/fixmap.h>
    > #include<asm/processor.h>
    > #include<asm/proto.h>
    > @@ -1198,3 +1201,115 @@ asmlinkage void __init xen_start_kernel(void)
    > x86_64_start_reservations((char *)__pa_symbol(&boot_params));
    > #endif
    > }
    > +
    > +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 featured 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 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;
    > +}
    > +
    > +u32 xen_hvm_pv_status;
    > +EXPORT_SYMBOL_GPL(xen_hvm_pv_status);
    > +
    > +static int 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_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;
    > +
    > + xen_hvm_pv_status = XEN_HVM_PV_ENABLED;
    >

    Why use this? Why not just set the domain type to HVM, and leave the
    "status" field as a bitset of available paravirtualizations?

    > +
    > + /* We only support 1 page of hypercall for now */
    > + if (pages != 1)
    > + return -ENOMEM;
    > +
    > + pfn = __pa(hypercall_page);
    > + wrmsrl(msr, pfn);
    > +
    > + xen_setup_features();
    > +
    > + x86_init.oem.banner = xen_hvm_pv_banner;
    > + pv_info = xen_info;
    > + pv_info.kernel_rpl = 0;
    > +
    > + return 0;
    > +}
    > +
    > +extern struct shared_info shared_info_page;
    > +
    > +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();
    > +
    > + HYPERVISOR_shared_info = (struct shared_info *)&shared_info_page;
    > +
    > + /* Don't do the full vcpu_info placement stuff until we have a
    > + possible map and a non-dummy shared_info. */
    >

    Is this comment meaningful here? This is the real shared info at this
    point, no? Are you going to support vcpu_info placement?

    > + per_cpu(xen_vcpu, 0) =&HYPERVISOR_shared_info->vcpu_info[0];
    > +}
    > +
    > +void __init xen_guest_init(void)
    > +{
    > +#ifdef CONFIG_X86_32
    > + return;
    > +#else
    > + int r;
    > +
    > + /* Ensure the we won't confused with PV */
    > + if (xen_domain_type == XEN_PV_DOMAIN)
    > + return;
    >

    Aren't you specifically testing for xen_domain_type == NATIVE here? If
    its anything else, then it means we're either PV, or have become an HVM
    domain some other way (like probing for the Xen platform PCI device).



    > +
    > + r = init_hvm_pv_info();
    > + if (r< 0)
    > + return;
    > +
    > + init_shared_info();
    > +
    > + xen_hvm_pv_init_irq_ops();
    > +#endif
    > +}
    >

    Can you split all this off into a new file. It doesn't seem to have any
    dependencies on the rest of enlighten.c, and I've been trying to
    disaggregate it anyway.

    > +
    > diff --git a/arch/x86/xen/irq.c b/arch/x86/xen/irq.c
    > index 9d30105..fadaa97 100644
    > --- a/arch/x86/xen/irq.c
    > +++ b/arch/x86/xen/irq.c
    > @@ -131,3 +131,24 @@ void __init xen_init_irq_ops()
    > pv_irq_ops = xen_irq_ops;
    > x86_init.irqs.intr_init = xen_init_IRQ;
    > }
    > +
    > +static void xen_hvm_pv_safe_halt(void)
    > +{
    > + /* Do local_irq_enable() explicitly in hvm_pv guest */
    > + local_irq_enable();
    > + xen_safe_halt();
    > +}
    > +
    > +static void xen_hvm_pv_halt(void)
    > +{
    > + if (irqs_disabled())
    > + HYPERVISOR_vcpu_op(VCPUOP_down, smp_processor_id(), NULL);
    > + else
    > + xen_hvm_pv_safe_halt();
    > +}
    > +
    > +void __init xen_hvm_pv_init_irq_ops(void)
    > +{
    > + pv_irq_ops.safe_halt = xen_hvm_pv_safe_halt;
    > + pv_irq_ops.halt = xen_hvm_pv_halt;
    > +}
    >

    It would be better to make this patch purely common infrastructure, and
    make specific features (like hvm+pv halt) separate patches (one per patch).

    > diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S
    > index 1a5ff24..26041ce 100644
    > --- a/arch/x86/xen/xen-head.S
    > +++ b/arch/x86/xen/xen-head.S
    > @@ -33,6 +33,12 @@ ENTRY(hypercall_page)
    > .skip PAGE_SIZE_asm
    > .popsection
    >
    > +.pushsection .data
    > + .align PAGE_SIZE_asm
    > +ENTRY(shared_info_page)
    > + .skip PAGE_SIZE_asm
    > +.popsection
    >

    Why does this need to be defined in asm? Can't it be either allocated
    or defined in C?

    > +
    > ELFNOTE(Xen, XEN_ELFNOTE_GUEST_OS, .asciz "linux")
    > ELFNOTE(Xen, XEN_ELFNOTE_GUEST_VERSION, .asciz "2.6")
    > ELFNOTE(Xen, XEN_ELFNOTE_XEN_VERSION, .asciz "xen-3.0")
    > diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
    > index f9153a3..cc00760 100644
    > --- a/arch/x86/xen/xen-ops.h
    > +++ b/arch/x86/xen/xen-ops.h
    > @@ -41,6 +41,7 @@ void xen_vcpu_restore(void);
    > void __init xen_build_dynamic_phys_to_machine(void);
    >
    > void xen_init_irq_ops(void);
    > +void xen_hvm_pv_init_irq_ops(void);
    > void xen_setup_timer(int cpu);
    > void xen_setup_runstate_info(int cpu);
    > void xen_teardown_timer(int cpu);
    > diff --git a/include/xen/interface/hvm/hvm_op.h b/include/xen/interface/hvm/hvm_op.h
    > index 7c74ba4..0ce8a26 100644
    > --- a/include/xen/interface/hvm/hvm_op.h
    > +++ b/include/xen/interface/hvm/hvm_op.h
    > @@ -69,4 +69,11 @@ 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_EVTCHN (1ull<<1)
    > +};
    > +
    > #endif /* __XEN_PUBLIC_HVM_HVM_OP_H__ */
    > diff --git a/include/xen/xen.h b/include/xen/xen.h
    > index a164024..9bb92e5 100644
    > --- a/include/xen/xen.h
    > +++ b/include/xen/xen.h
    > @@ -9,6 +9,7 @@ enum xen_domain_type {
    >
    > #ifdef CONFIG_XEN
    > extern enum xen_domain_type xen_domain_type;
    > +extern void xen_guest_init(void);
    > #else
    > #define xen_domain_type XEN_NATIVE
    > #endif
    > @@ -19,6 +20,14 @@ extern enum xen_domain_type xen_domain_type;
    > #define xen_hvm_domain() (xen_domain()&& \
    > xen_domain_type == XEN_HVM_DOMAIN)
    >
    > +#define XEN_HVM_PV_ENABLED (1u<< 0)
    >

    Why have this? We already have xen_domain_type which will either be
    XEN_NATIVE (ie, either real native, or on some fully emulated
    environment we have no specific optimisations for), or XEN_HVM_DOMAIN
    (we know we're running under Xen as an HVM domain).

    > +#define XEN_HVM_PV_EVTCHN_ENABLED (1u<< 1)
    > +extern u32 xen_hvm_pv_status;
    >

    I think "status" is a misnomer here. Isn't it specifically a set of PV
    features which are active?

    > +
    > +#define xen_hvm_pv_enabled() (xen_hvm_pv_status& XEN_HVM_PV_ENABLED)
    > +#define xen_hvm_pv_evtchn_enabled() (xen_hvm_pv_enabled()&& \
    > + (xen_hvm_pv_status& XEN_HVM_PV_EVTCHN_ENABLED))
    >

    Testing for xen_hvm_pv_enabled() should be redundant; surely the
    status/feature flag won't be set unless the environment supports the
    feature, and if it does it doesn't really matter what the domain type is.

    > +
    > #ifdef CONFIG_XEN_DOM0
    > #include<xen/interface/xen.h>
    > #include<asm/xen/hypervisor.h>
    >

    J


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