Pavel Tatashin
2021-Jan-20 16:03 UTC
[PATCH v5 02/16] x86/hyperv: detect if Linux is the root partition
On Wed, Jan 20, 2021 at 7:01 AM Wei Liu <wei.liu at kernel.org> wrote:> > 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 at kernel.org> > --- > v3: move hv_root_partition to mshyperv.c > --- > arch/x86/include/asm/hyperv-tlfs.h | 10 ++++++++++ > arch/x86/include/asm/mshyperv.h | 2 ++ > arch/x86/kernel/cpu/mshyperv.c | 20 ++++++++++++++++++++ > 3 files changed, 32 insertions(+) > > diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h > index 6bf42aed387e..204010350604 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_CPUID_VIRT_STACK_INTERFACE 0x40000081 > @@ -110,6 +111,15 @@ > /* 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; > + > #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 f628e3dc150f..c376d191a260 100644 > --- a/arch/x86/kernel/cpu/mshyperv.c > +++ b/arch/x86/kernel/cpu/mshyperv.c > @@ -32,6 +32,10 @@ > #include <asm/nmi.h> > #include <clocksource/hyperv_timer.h> > > +/* Is Linux running as the root partition? */ > +bool hv_root_partition; > +EXPORT_SYMBOL_GPL(hv_root_partition); > + > struct ms_hyperv_info ms_hyperv; > EXPORT_SYMBOL_GPL(ms_hyperv); > > @@ -237,6 +241,22 @@ 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).Is this comment relevant? Do we have to mirror what Windows does?> + * > + * For now, use the privilege flag as the indicator for running as > + * root. > + */ > + if (cpuid_ebx(HYPERV_CPUID_FEATURES) & HV_CPU_MANAGEMENT) { > + hv_root_partition = true; > + pr_info("Hyper-V: running as root partition\n"); > + } > +Reviewed-by: Pavel Tatashin <pasha.tatashin at soleen.com>> /* > * Extract host information. > */ > -- > 2.20.1 >