Re: [Xen-devel] [PATCH v7 05/10] x86/hyperv: setup hypercall page
> -Original Message-
> From: Wei Liu On Behalf Of Wei Liu
> Sent: 04 February 2020 15:37
> To: Xen Development List
> Cc: Durrant, Paul ; Michael Kelley
> ; Wei Liu ; Wei Liu
> ; Jan Beulich ; Andrew Cooper
> ; Roger Pau Monné
> 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
Acked-by: Paul Durrant
> ---
> 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
> +#include
>
> +#include
> #include
> #include
> +#include
>
> 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
> }
>
> +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_ID0x8300
> 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
Re: [Xen-devel] [PATCH v7 05/10] x86/hyperv: setup hypercall page
On Wed, Feb 05, 2020 at 03:00:24PM +, Wei Liu wrote:
> On Wed, Feb 05, 2020 at 03:04:16PM +0100, Roger Pau Monné wrote:
> [...]
> > > +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;
> >
> > Is it expected that the guest ID or the hypercal page is already
> > setup?
> >
> > Ie: would virtual firmware setup any of this? (and not clean it up
> > afterwards)
>
> There is no definitive answer to why/when this happens in TLFS, but it
> does require guest to respect that is already in the MSR.
My guess would be after migration Hyper-V sets up the same MSR/page
FWIW.
Wei.
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Re: [Xen-devel] [PATCH v7 05/10] x86/hyperv: setup hypercall page
On Wed, Feb 05, 2020 at 03:04:16PM +0100, Roger Pau Monné wrote:
[...]
> > +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;
>
> Is it expected that the guest ID or the hypercal page is already
> setup?
>
> Ie: would virtual firmware setup any of this? (and not clean it up
> afterwards)
There is no definitive answer to why/when this happens in TLFS, but it
does require guest to respect that is already in the MSR.
Wei.
>
> Thanks, Roger.
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Re: [Xen-devel] [PATCH v7 05/10] x86/hyperv: setup hypercall page
On Tue, Feb 04, 2020 at 03:36:59PM +, Wei Liu wrote:
> 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
Reviewed-by: Roger Pau Monné
> ---
> 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
> +#include
>
> +#include
> #include
> #include
> +#include
>
> 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
> }
>
> +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;
Is it expected that the guest ID or the hypercal page is already
setup?
Ie: would virtual firmware setup any of this? (and not clean it up
afterwards)
Thanks, Roger.
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