Re: [Xen-devel] [PATCH 3/7] xen/hvm: Xen PV extension of HVM initialization

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

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@xxxxxxxxxxxxxxx>
> Signed-off-by: Yaozu (Eddie) Dong<eddie.dong@xxxxxxxxx>
> ---
>   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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