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

[Tianyu Lan <ltykernel@xxxxxxxxx>]

From: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>

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.
+        */
+       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