Re: [Xen-devel] [PATCH 8/8] x86/hyperv: setup VP assist page

[Michael Kelley <mikelley@xxxxxxxxxxxxx>]

From: Wei Liu <wei.liu.xen@xxxxxxxxx> On Behalf Of Wei Liu  Sent: Sunday, 
December 29, 2019 10:34 AM
> 
> VP assist page is rather important as we need to toggle some bits in
> that page such that L1 guest can make hypercalls directly to L0 Hyper-V.
> 
> Preemptively split out set_vp_assist page which will be used in the resume
> path.
> 
> Signed-off-by: Wei Liu <liuwe@xxxxxxxxxxxxx>
> ---
>  xen/arch/x86/guest/hyperv/hyperv.c | 35 ++++++++++++++++++++++++++++++
>  xen/include/asm-x86/guest/hyperv.h |  1 +
>  2 files changed, 36 insertions(+)
> 
> diff --git a/xen/arch/x86/guest/hyperv/hyperv.c 
> b/xen/arch/x86/guest/hyperv/hyperv.c
> index da3a8cd85d..a88b9ae6d9 100644
> --- a/xen/arch/x86/guest/hyperv/hyperv.c
> +++ b/xen/arch/x86/guest/hyperv/hyperv.c
> @@ -30,6 +30,7 @@ void *hv_hypercall;
>  static struct page_info *hv_hypercall_page;
>  DEFINE_PER_CPU_READ_MOSTLY(struct hyperv_pcpu_page, hv_pcpu_input_arg);
>  DEFINE_PER_CPU_READ_MOSTLY(unsigned int, hv_vp_index);
> +DEFINE_PER_CPU_READ_MOSTLY(struct hyperv_pcpu_page, hv_vp_assist);
> 
>  static const struct hypervisor_ops ops;
>  const struct hypervisor_ops *__init hyperv_probe(void)
> @@ -125,17 +126,51 @@ static void setup_vp_index(void)
>      this_cpu(hv_vp_index) = vp_index_msr;
>  }
> 
> +static void set_vp_assist(void)
> +{
> +    uint64_t val = paddr_to_pfn(this_cpu(hv_vp_assist).maddr);
> +
> +    val = (val << HV_X64_MSR_VP_ASSIST_PAGE_ADDRESS_SHIFT) | 

I'd recommend using HV_HYP_PAGE_SHIFT instead of
HV_X64_MSR_VP_ASSIST_PAGE_ADDRESS_SHIFT.  On the Linux side,
I'm planning to remove that #define and the similar
*_PAGE_ADDRESS_MASK in favor of the newer HV_HYP_PAGE_* values.
There's nothing special about the VP assist page, so using the generic
#defines based on the Hyper-V page size is reasonable.

Michael

> +        HV_X64_MSR_VP_ASSIST_PAGE_ENABLE;
> +
> +    wrmsrl(HV_X64_MSR_VP_ASSIST_PAGE, val);
> +}
> +
> +static void setup_vp_assist(void)
> +{
> +    struct page_info *pg;
> +    void *mapping;
> +    unsigned int cpu = smp_processor_id();
> +
> +    pg = alloc_domheap_page(NULL, 0);
> +    if ( !pg )
> +        panic("Failed to allocate vp_assist page for %u\n", cpu);
> +
> +    mapping = __map_domain_page_global(pg);
> +    if ( !mapping )
> +        panic("Failed to map vp_assist page for %u\n", cpu);
> +
> +    clear_page(mapping);
> +
> +    this_cpu(hv_vp_assist).maddr = page_to_maddr(pg);
> +    this_cpu(hv_vp_assist).mapping = mapping;
> +
> +    set_vp_assist();
> +}
> +
>  static void __init setup(void)
>  {
>      setup_hypercall_page();
>      setup_hypercall_pcpu_arg();
>      setup_vp_index();
> +    setup_vp_assist();
>  }
> 
>  static void ap_setup(void)
>  {
>      setup_hypercall_pcpu_arg();
>      setup_vp_index();
> +    setup_vp_assist();
>  }
> 
>  static const struct hypervisor_ops ops = {
> diff --git a/xen/include/asm-x86/guest/hyperv.h 
> b/xen/include/asm-x86/guest/hyperv.h
> index 4b635829f3..917f4e02c2 100644
> --- a/xen/include/asm-x86/guest/hyperv.h
> +++ b/xen/include/asm-x86/guest/hyperv.h
> @@ -71,6 +71,7 @@ struct hyperv_pcpu_page {
>  };
>  DECLARE_PER_CPU(struct hyperv_pcpu_page, hv_pcpu_input_arg);
>  DECLARE_PER_CPU(unsigned int, hv_vp_index);
> +DECLARE_PER_CPU(struct hyperv_pcpu_page, hv_vp_assist);
> 
>  const struct hypervisor_ops *hyperv_probe(void);
> 
> --
> 2.20.1


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel