RE: [PATCH V4 01/13] x86/hyperv: Initialize GHCB page in Isolation VM

[Michael Kelley]

From: Tianyu Lan <ltykernel@xxxxxxxxx> Sent: Friday, August 27, 2021 10:21 AM
> 
> Hyperv exposes GHCB page via SEV ES GHCB MSR for SNP guest
> to communicate with hypervisor. Map GHCB page for all
> cpus to read/write MSR register and submit hvcall request
> via ghcb page.
> 
> Signed-off-by: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>
> ---
> Chagne since v3:
>         * Rename ghcb_base to hv_ghcb_pg and move it out of
> 	  struct ms_hyperv_info.
> 	* Allocate hv_ghcb_pg before cpuhp_setup_state() and leverage
> 	  hv_cpu_init() to initialize ghcb page.
> ---
>  arch/x86/hyperv/hv_init.c       | 68 +++++++++++++++++++++++++++++----
>  arch/x86/include/asm/mshyperv.h |  4 ++
>  arch/x86/kernel/cpu/mshyperv.c  |  3 ++
>  include/asm-generic/mshyperv.h  |  1 +
>  4 files changed, 69 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index 708a2712a516..eba10ed4f73e 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -20,6 +20,7 @@
>  #include <linux/kexec.h>
>  #include <linux/version.h>
>  #include <linux/vmalloc.h>
> +#include <linux/io.h>
>  #include <linux/mm.h>
>  #include <linux/hyperv.h>
>  #include <linux/slab.h>
> @@ -36,12 +37,42 @@ EXPORT_SYMBOL_GPL(hv_current_partition_id);
>  void *hv_hypercall_pg;
>  EXPORT_SYMBOL_GPL(hv_hypercall_pg);
> 
> +void __percpu **hv_ghcb_pg;
> +
>  /* Storage to save the hypercall page temporarily for hibernation */
>  static void *hv_hypercall_pg_saved;
> 
>  struct hv_vp_assist_page **hv_vp_assist_page;
>  EXPORT_SYMBOL_GPL(hv_vp_assist_page);
> 
> +static int hyperv_init_ghcb(void)
> +{
> +	u64 ghcb_gpa;
> +	void *ghcb_va;
> +	void **ghcb_base;
> +
> +	if (!hv_isolation_type_snp())
> +		return 0;
> +
> +	if (!hv_ghcb_pg)
> +		return -EINVAL;
> +
> +	/*
> +	 * GHCB page is allocated by paravisor. The address
> +	 * returned by MSR_AMD64_SEV_ES_GHCB is above shared
> +	 * ghcb boundary and map it here.

I'm not sure what the "shared ghcb boundary" is.  Did you
mean "shared_gpa_boundary"?

> +	 */
> +	rdmsrl(MSR_AMD64_SEV_ES_GHCB, ghcb_gpa);
> +	ghcb_va = memremap(ghcb_gpa, HV_HYP_PAGE_SIZE, MEMREMAP_WB);
> +	if (!ghcb_va)
> +		return -ENOMEM;
> +
> +	ghcb_base = (void **)this_cpu_ptr(hv_ghcb_pg);
> +	*ghcb_base = ghcb_va;
> +
> +	return 0;
> +}
> +
>  static int hv_cpu_init(unsigned int cpu)
>  {
>  	union hv_vp_assist_msr_contents msr = { 0 };
> @@ -85,7 +116,7 @@ static int hv_cpu_init(unsigned int cpu)
>  		}
>  	}
> 
> -	return 0;
> +	return hyperv_init_ghcb();
>  }
> 
>  static void (*hv_reenlightenment_cb)(void);
> @@ -177,6 +208,14 @@ static int hv_cpu_die(unsigned int cpu)
>  {
>  	struct hv_reenlightenment_control re_ctrl;
>  	unsigned int new_cpu;
> +	void **ghcb_va;
> +
> +	if (hv_ghcb_pg) {
> +		ghcb_va = (void **)this_cpu_ptr(hv_ghcb_pg);
> +		if (*ghcb_va)
> +			memunmap(*ghcb_va);
> +		*ghcb_va = NULL;
> +	}
> 
>  	hv_common_cpu_die(cpu);
> 
> @@ -366,10 +405,16 @@ void __init hyperv_init(void)
>  		goto common_free;
>  	}
> 
> +	if (hv_isolation_type_snp()) {
> +		hv_ghcb_pg = alloc_percpu(void *);
> +		if (!hv_ghcb_pg)
> +			goto free_vp_assist_page;
> +	}
> +
>  	cpuhp = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/hyperv_init:online",
>  				  hv_cpu_init, hv_cpu_die);
>  	if (cpuhp < 0)
> -		goto free_vp_assist_page;
> +		goto free_ghcb_page;
> 
>  	/*
>  	 * Setup the hypercall page and enable hypercalls.
> @@ -383,10 +428,8 @@ void __init hyperv_init(void)
>  			VMALLOC_END, GFP_KERNEL, PAGE_KERNEL_ROX,
>  			VM_FLUSH_RESET_PERMS, NUMA_NO_NODE,
>  			__builtin_return_address(0));
> -	if (hv_hypercall_pg == NULL) {
> -		wrmsrl(HV_X64_MSR_GUEST_OS_ID, 0);
> -		goto remove_cpuhp_state;
> -	}
> +	if (hv_hypercall_pg == NULL)
> +		goto clean_guest_os_id;
> 
>  	rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
>  	hypercall_msr.enable = 1;
> @@ -456,8 +499,11 @@ void __init hyperv_init(void)
>  	hv_query_ext_cap(0);
>  	return;
> 
> -remove_cpuhp_state:
> +clean_guest_os_id:
> +	wrmsrl(HV_X64_MSR_GUEST_OS_ID, 0);
>  	cpuhp_remove_state(cpuhp);
> +free_ghcb_page:
> +	free_percpu(hv_ghcb_pg);
>  free_vp_assist_page:
>  	kfree(hv_vp_assist_page);
>  	hv_vp_assist_page = NULL;
> @@ -559,3 +605,11 @@ bool hv_is_isolation_supported(void)
>  {
>  	return hv_get_isolation_type() != HV_ISOLATION_TYPE_NONE;
>  }
> +
> +DEFINE_STATIC_KEY_FALSE(isolation_type_snp);
> +
> +bool hv_isolation_type_snp(void)
> +{
> +	return static_branch_unlikely(&isolation_type_snp);
> +}
> +EXPORT_SYMBOL_GPL(hv_isolation_type_snp);
> diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
> index adccbc209169..37739a277ac6 100644
> --- a/arch/x86/include/asm/mshyperv.h
> +++ b/arch/x86/include/asm/mshyperv.h
> @@ -11,6 +11,8 @@
>  #include <asm/paravirt.h>
>  #include <asm/mshyperv.h>
> 
> +DECLARE_STATIC_KEY_FALSE(isolation_type_snp);
> +
>  typedef int (*hyperv_fill_flush_list_func)(
>  		struct hv_guest_mapping_flush_list *flush,
>  		void *data);
> @@ -39,6 +41,8 @@ extern void *hv_hypercall_pg;
> 
>  extern u64 hv_current_partition_id;
> 
> +extern void __percpu **hv_ghcb_pg;
> +
>  int hv_call_deposit_pages(int node, u64 partition_id, u32 num_pages);
>  int hv_call_add_logical_proc(int node, u32 lp_index, u32 acpi_id);
>  int hv_call_create_vp(int node, u64 partition_id, u32 vp_index, u32 flags);
> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> index 6b5835a087a3..20557a9d6e25 100644
> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -316,6 +316,9 @@ static void __init ms_hyperv_init_platform(void)
> 
>  		pr_info("Hyper-V: Isolation Config: Group A 0x%x, Group B 0x%x\n",
>  			ms_hyperv.isolation_config_a, ms_hyperv.isolation_config_b);
> +
> +		if (hv_get_isolation_type() == HV_ISOLATION_TYPE_SNP)
> +			static_branch_enable(&isolation_type_snp);
>  	}
> 
>  	if (hv_max_functions_eax >= HYPERV_CPUID_NESTED_FEATURES) {
> diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
> index c1ab6a6e72b5..0924bbd8458e 100644
> --- a/include/asm-generic/mshyperv.h
> +++ b/include/asm-generic/mshyperv.h
> @@ -237,6 +237,7 @@ bool hv_is_hyperv_initialized(void);
>  bool hv_is_hibernation_supported(void);
>  enum hv_isolation_type hv_get_isolation_type(void);
>  bool hv_is_isolation_supported(void);
> +bool hv_isolation_type_snp(void);
>  void hyperv_cleanup(void);
>  bool hv_query_ext_cap(u64 cap_query);
>  #else /* CONFIG_HYPERV */
> --
> 2.25.1