Wei Liu <wei.liu@xxxxxxxxxx> writes:
> For now we can use the privilege flag to check. Stash the value to be
> used later.
>
> Put in a bunch of defines for future use when we want to have more
> fine-grained detection.
>
> Signed-off-by: Wei Liu <wei.liu@xxxxxxxxxx>
> ---
> arch/x86/hyperv/hv_init.c | 4 ++++
> arch/x86/include/asm/hyperv-tlfs.h | 10 ++++++++++
> arch/x86/include/asm/mshyperv.h | 2 ++
> arch/x86/kernel/cpu/mshyperv.c | 16 ++++++++++++++++
> 4 files changed, 32 insertions(+)
>
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index e04d90af4c27..533fe9e887f2 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -26,6 +26,10 @@
> #include <linux/syscore_ops.h>
> #include <clocksource/hyperv_timer.h>
>
> +/* Is Linux running as the root partition? */
> +bool hv_root_partition;
> +EXPORT_SYMBOL_GPL(hv_root_partition);
(Nitpick and rather a personal preference): I'd prefer
'hv_partition_is_root' for a boolean.
> +
> void *hv_hypercall_pg;
> EXPORT_SYMBOL_GPL(hv_hypercall_pg);
>
> diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
> index 0ed20e8bba9e..41b628b9fb15 100644
> --- a/arch/x86/include/asm/hyperv-tlfs.h
> +++ b/arch/x86/include/asm/hyperv-tlfs.h
> @@ -21,6 +21,7 @@
> #define HYPERV_CPUID_FEATURES 0x40000003
> #define HYPERV_CPUID_ENLIGHTMENT_INFO 0x40000004
> #define HYPERV_CPUID_IMPLEMENT_LIMITS 0x40000005
> +#define HYPERV_CPUID_CPU_MANAGEMENT_FEATURES 0x40000007
> #define HYPERV_CPUID_NESTED_FEATURES 0x4000000A
>
> #define HYPERV_HYPERVISOR_PRESENT_BIT 0x80000000
> @@ -103,6 +104,15 @@
> /* Recommend using enlightened VMCS */
> #define HV_X64_ENLIGHTENED_VMCS_RECOMMENDED BIT(14)
>
> +/*
> + * CPU management features identification.
> + * These are HYPERV_CPUID_CPU_MANAGEMENT_FEATURES.EAX bits.
> + */
> +#define HV_X64_START_LOGICAL_PROCESSOR BIT(0)
> +#define HV_X64_CREATE_ROOT_VIRTUAL_PROCESSOR BIT(1)
> +#define HV_X64_PERFORMANCE_COUNTER_SYNC BIT(2)
> +#define HV_X64_RESERVED_IDENTITY_BIT BIT(31)
> +
> /*
> * Virtual processor will never share a physical core with another virtual
> * processor, except for virtual processors that are reported as sibling SMT
> diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
> index ffc289992d1b..ac2b0d110f03 100644
> --- a/arch/x86/include/asm/mshyperv.h
> +++ b/arch/x86/include/asm/mshyperv.h
> @@ -237,6 +237,8 @@ int hyperv_fill_flush_guest_mapping_list(
> struct hv_guest_mapping_flush_list *flush,
> u64 start_gfn, u64 end_gfn);
>
> +extern bool hv_root_partition;
Eventually this is not going to be an x86 only thing I believe?
> +
> #ifdef CONFIG_X86_64
> void hv_apic_init(void);
> void __init hv_init_spinlocks(void);
> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> index 05ef1f4550cb..f7633e1e4c82 100644
> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -237,6 +237,22 @@ static void __init ms_hyperv_init_platform(void)
> pr_debug("Hyper-V: max %u virtual processors, %u logical processors\n",
> ms_hyperv.max_vp_index, ms_hyperv.max_lp_index);
>
> + /*
> + * Check CPU management privilege.
> + *
> + * To mirror what Windows does we should extract CPU management
> + * features and use the ReservedIdentityBit to detect if Linux is the
> + * root partition. But that requires negotiating CPU management
> + * interface (a process to be finalized).
> + *
> + * For now, use the privilege flag as the indicator for running as
> + * root.
> + */
> + if (cpuid_ebx(HYPERV_CPUID_FEATURES) & HV_CPU_MANAGEMENT) {
We may want to cache cpuid_ebx(HYPERV_CPUID_FEATURES) somewhere but we
already had a discussion regading naming for these caches and decided to
wait until TLFS for ARM is out so we don't need to rename again.
> + hv_root_partition = true;
> + pr_info("Hyper-V: running as root partition\n");
> + }
> +
> /*
> * Extract host information.
> */
Reviewed-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
--
Vitaly
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