On 22/01/2020 20:23, Wei Liu wrote:
> Use the top-most addressable page for that purpose. Adjust e820 code
> accordingly.
>
> We also need to register Xen's guest OS ID to Hyper-V. Use 0x300 as the
> OS type.
>
> Signed-off-by: Wei Liu <li...@microsoft.com>
> ---
> XXX the decision on Xen's vendor ID is pending.
Presumably this is pending a published update to the TLFS? (And I
presume using 0x8088 is out of the question? That is an X in the bottom
byte, not a reference to an 8 bit microprocessor.)
> diff --git a/xen/arch/x86/e820.c b/xen/arch/x86/e820.c
> index 082f9928a1..5a4ef27a0b 100644
> --- a/xen/arch/x86/e820.c
> +++ b/xen/arch/x86/e820.c
> @@ -36,6 +36,22 @@ boolean_param("e820-verbose", e820_verbose);
> @@ -357,6 +373,21 @@ static unsigned long __init find_max_pfn(void)
> max_pfn = end;
> }
>
> +#ifdef CONFIG_HYPERV_GUEST
> + {
> + /*
> + * We reserve the top-most page for hypercall page. Adjust
> + * max_pfn if necessary.
It might be worth leaving a "TODO: Better algorithm/guess?" here.
> + */
> + unsigned int phys_bits = find_phys_addr_bits();
> + unsigned long hcall_pfn =
> + ((1ull << phys_bits) - 1) >> PAGE_SHIFT;
(1ull << (phys_bits - PAGE_SHIFT)) - 1 is equivalent, and doesn't
require a right shift. I don't know if the compiler is smart enough to
make this optimisation automatically.
> +
> + if ( max_pfn >= hcall_pfn )
> + max_pfn = hcall_pfn - 1;
Indentation looks weird.
> @@ -446,13 +477,7 @@ static uint64_t __init mtrr_top_of_ram(void)
> return 0;
>
> /* Find the physical address size for this CPU. */
> - eax = cpuid_eax(0x80000000);
> - if ( (eax >> 16) == 0x8000 && eax >= 0x80000008 )
> - {
> - phys_bits = (uint8_t)cpuid_eax(0x80000008);
> - if ( phys_bits > PADDR_BITS )
> - phys_bits = PADDR_BITS;
> - }
> + phys_bits = find_phys_addr_bits();
> addr_mask = ((1ull << phys_bits) - 1) & ~((1ull << 12) - 1);
Note for whomever is next doing cleanup in this area. This wants to be
& PAGE_MASK.
> diff --git a/xen/arch/x86/guest/hyperv/hyperv.c
> b/xen/arch/x86/guest/hyperv/hyperv.c
> index 8d38313d7a..f986c1a805 100644
> --- a/xen/arch/x86/guest/hyperv/hyperv.c
> +++ b/xen/arch/x86/guest/hyperv/hyperv.c
> @@ -72,6 +82,43 @@ 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;
> +
> + 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 = ((1ull << paddr_bits) - 1) >> HV_HYP_PAGE_SHIFT;
> + hypercall_msr.enable = 1;
> + hypercall_msr.guest_physical_address = mfn;
> + wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
Is it worth reading back, and BUG() if it is different? It will be a
more obvious failure than hypercalls disappearing mysteriously.
> + } else {
> + mfn = hypercall_msr.guest_physical_address;
> + }
Style.
Otherwise, LGTM.
~Andrew
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