Re: [Xen-devel] [PATCH v7 05/10] x86/hyperv: setup hypercall page

["Durrant, Paul" <pdurrant@xxxxxxxxxxxx>]

> -----Original Message-----
> From: Wei Liu <wei.liu.xen@xxxxxxxxx> On Behalf Of Wei Liu
> Sent: 04 February 2020 15:37
> To: Xen Development List <xen-devel@xxxxxxxxxxxxxxxxxxxx>
> Cc: Durrant, Paul <pdurrant@xxxxxxxxxxxx>; Michael Kelley
> <mikelley@xxxxxxxxxxxxx>; Wei Liu <liuwe@xxxxxxxxxxxxx>; Wei Liu
> <wl@xxxxxxx>; Jan Beulich <jbeulich@xxxxxxxx>; Andrew Cooper
> <andrew.cooper3@xxxxxxxxxx>; Roger Pau Monné <roger.pau@xxxxxxxxxx>
> Subject: [PATCH v7 05/10] x86/hyperv: setup hypercall page
> 
> Hyper-V uses a technique called overlay page for its hypercall page. It
> will insert a backing page to the guest when the hypercall functionality
> is enabled. That means we can use a page that is not backed by real
> memory for hypercall page.
> 
> To avoid shattering L0 superpages and treading on any MMIO areas
> residing in low addresses, use the top-most addressable page for that
> purpose. Adjust e820 map accordingly.
> 
> We also need to register Xen's guest OS ID to Hyper-V. Use 0x3 as the
> vendor ID. Fix the comment in hyperv-tlfs.h while at it.
> 
> Signed-off-by: Wei Liu <liuwe@xxxxxxxxxxxxx>

Acked-by: Paul Durrant <pdurrant@xxxxxxxxxx>

> ---
> v7:
> 1. Fix a style issue
> 2. Initialise ID to 0
> 3. Update commit message
> 
> v6:
> 1. Use hv_guest_os_id
> 2. Use new e820_fixup hook
> 3. Add a BUILD_BUG_ON
> 
> v5:
> 1. use hypervisor_reserve_top_pages
> 2. add a macro for hypercall page mfn
> 3. address other misc comments
> 
> v4:
> 1. Use fixmap
> 2. Follow routines listed in TLFS
> ---
>  xen/arch/x86/guest/hyperv/hyperv.c      | 69 +++++++++++++++++++++++--
>  xen/include/asm-x86/guest/hyperv-tlfs.h |  5 +-
>  xen/include/asm-x86/guest/hyperv.h      |  3 ++
>  3 files changed, 72 insertions(+), 5 deletions(-)
> 
> diff --git a/xen/arch/x86/guest/hyperv/hyperv.c
> b/xen/arch/x86/guest/hyperv/hyperv.c
> index 8d38313d7a..2e20a96f30 100644
> --- a/xen/arch/x86/guest/hyperv/hyperv.c
> +++ b/xen/arch/x86/guest/hyperv/hyperv.c
> @@ -19,15 +19,27 @@
>   * Copyright (c) 2019 Microsoft.
>   */
>  #include <xen/init.h>
> +#include <xen/version.h>
> 
> +#include <asm/fixmap.h>
>  #include <asm/guest.h>
>  #include <asm/guest/hyperv-tlfs.h>
> +#include <asm/processor.h>
> 
>  struct ms_hyperv_info __read_mostly ms_hyperv;
> 
> -static const struct hypervisor_ops ops = {
> -    .name = "Hyper-V",
> -};
> +static uint64_t generate_guest_id(void)
> +{
> +    union hv_guest_os_id id = {};
> +
> +    id.vendor = HV_XEN_VENDOR_ID;
> +    id.major = xen_major_version();
> +    id.minor = xen_minor_version();
> +
> +    return id.raw;
> +}
> +
> +static const struct hypervisor_ops ops;
> 
>  const struct hypervisor_ops *__init hyperv_probe(void)
>  {
> @@ -72,6 +84,57 @@ const struct hypervisor_ops *__init hyperv_probe(void)
>      return &ops;
>  }
> 
> +static void __init setup_hypercall_page(void)
> +{
> +    union hv_x64_msr_hypercall_contents hypercall_msr;
> +    union hv_guest_os_id guest_id;
> +    unsigned long mfn;
> +
> +    BUILD_BUG_ON(HV_HYP_PAGE_SHIFT != PAGE_SHIFT);
> +
> +    rdmsrl(HV_X64_MSR_GUEST_OS_ID, guest_id.raw);
> +    if ( !guest_id.raw )
> +    {
> +        guest_id.raw = generate_guest_id();
> +        wrmsrl(HV_X64_MSR_GUEST_OS_ID, guest_id.raw);
> +    }
> +
> +    rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
> +    if ( !hypercall_msr.enable )
> +    {
> +        mfn = HV_HCALL_MFN;
> +        hypercall_msr.enable = 1;
> +        hypercall_msr.guest_physical_address = mfn;
> +        wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
> +    }
> +    else
> +        mfn = hypercall_msr.guest_physical_address;
> +
> +    rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
> +    BUG_ON(!hypercall_msr.enable);
> +
> +    set_fixmap_x(FIX_X_HYPERV_HCALL, mfn << PAGE_SHIFT);
> +}
> +
> +static void __init setup(void)
> +{
> +    setup_hypercall_page();
> +}
> +
> +static void __init e820_fixup(struct e820map *e820)
> +{
> +    uint64_t s = HV_HCALL_MFN << PAGE_SHIFT;
> +
> +    if ( !e820_add_range(e820, s, s + PAGE_SIZE, E820_RESERVED) )
> +        panic("Unable to reserve Hyper-V hypercall range\n");
> +}
> +
> +static const struct hypervisor_ops ops = {
> +    .name = "Hyper-V",
> +    .setup = setup,
> +    .e820_fixup = e820_fixup,
> +};
> +
>  /*
>   * Local variables:
>   * mode: C
> diff --git a/xen/include/asm-x86/guest/hyperv-tlfs.h b/xen/include/asm-
> x86/guest/hyperv-tlfs.h
> index 091e25cdd1..0a0f3398c1 100644
> --- a/xen/include/asm-x86/guest/hyperv-tlfs.h
> +++ b/xen/include/asm-x86/guest/hyperv-tlfs.h
> @@ -318,15 +318,16 @@ struct ms_hyperv_tsc_page {
>   *
>   * Bit(s)
>   * 63 - Indicates if the OS is Open Source or not; 1 is Open Source
> - * 62:56 - Os Type; Linux is 0x100
> + * 62:56 - Os Type; Linux 0x1, FreeBSD 0x2, Xen 0x3
>   * 55:48 - Distro specific identification
> - * 47:16 - Linux kernel version number
> + * 47:16 - Guest OS version number
>   * 15:0  - Distro specific identification
>   *
>   *
>   */
> 
>  #define HV_LINUX_VENDOR_ID              0x8100
> +#define HV_XEN_VENDOR_ID                0x8300
>  union hv_guest_os_id
>  {
>      uint64_t raw;
> diff --git a/xen/include/asm-x86/guest/hyperv.h b/xen/include/asm-
> x86/guest/hyperv.h
> index c7a7f32bd5..1a1b47831c 100644
> --- a/xen/include/asm-x86/guest/hyperv.h
> +++ b/xen/include/asm-x86/guest/hyperv.h
> @@ -21,6 +21,9 @@
> 
>  #include <xen/types.h>
> 
> +/* Use top-most MFN for hypercall page */
> +#define HV_HCALL_MFN   (((1ull << paddr_bits) - 1) >> HV_HYP_PAGE_SHIFT)
> +
>  /*
>   * The specification says: "The partition reference time is computed
>   * by the following formula:
> --
> 2.20.1


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