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[91.219.240.2]) by smtp.gmail.com with ESMTPSA id y11sm6415716wmj.36.2020.11.12.07.16.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 12 Nov 2020 07:16:32 -0800 (PST) From: Vitaly Kuznetsov To: Wei Liu , Linux on Hyper-V List Cc: virtualization@lists.linux-foundation.org, Linux Kernel List , Michael Kelley , Vineeth Pillai , Sunil Muthuswamy , Nuno Das Neves , Wei Liu , "K. Y. Srinivasan" , Haiyang Zhang , Stephen Hemminger , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , "H. Peter Anvin" Subject: Re: [PATCH v2 02/17] x86/hyperv: detect if Linux is the root partition In-Reply-To: <20201105165814.29233-3-wei.liu@kernel.org> References: <20201105165814.29233-1-wei.liu@kernel.org> <20201105165814.29233-3-wei.liu@kernel.org> Date: Thu, 12 Nov 2020 16:16:30 +0100 Message-ID: <87lff6y59t.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Wei Liu 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 > --- > 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 > #include > > +/* 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 -- Vitaly