[PATCH V2 01/14] x86/HV: Initialize GHCB page in Isolation VM

[Tianyu Lan <ltykernel@xxxxxxxxx>]

From: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>

Hyper-V 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.

Signed-off-by: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>
---
 arch/x86/hyperv/hv_init.c       | 69 +++++++++++++++++++++++++++++++--
 arch/x86/include/asm/mshyperv.h |  2 +
 include/asm-generic/mshyperv.h  |  2 +
 3 files changed, 69 insertions(+), 4 deletions(-)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 4a643a85d570..247df301491f 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>
@@ -42,6 +43,31 @@ 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 (!ms_hyperv.ghcb_base)
+               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(ms_hyperv.ghcb_base);
+       *ghcb_base = ghcb_va;
+
+       return 0;
+}
+
 static int hv_cpu_init(unsigned int cpu)
 {
        struct hv_vp_assist_page **hvp = &hv_vp_assist_page[smp_processor_id()];
@@ -75,6 +101,8 @@ static int hv_cpu_init(unsigned int cpu)
                wrmsrl(HV_X64_MSR_VP_ASSIST_PAGE, val);
        }
 
+       hyperv_init_ghcb();
+
        return 0;
 }
 
@@ -167,6 +195,14 @@ static int hv_cpu_die(unsigned int cpu)
 {
        struct hv_reenlightenment_control re_ctrl;
        unsigned int new_cpu;
+       void **ghcb_va = NULL;
+
+       if (ms_hyperv.ghcb_base) {
+               ghcb_va = (void **)this_cpu_ptr(ms_hyperv.ghcb_base);
+               if (*ghcb_va)
+                       memunmap(*ghcb_va);
+               *ghcb_va = NULL;
+       }
 
        hv_common_cpu_die(cpu);
 
@@ -340,9 +376,22 @@ 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;
+
+       if (hv_isolation_type_snp()) {
+               ms_hyperv.ghcb_base = alloc_percpu(void *);
+               if (!ms_hyperv.ghcb_base)
+                       goto clean_guest_os_id;
+
+               if (hyperv_init_ghcb()) {
+                       free_percpu(ms_hyperv.ghcb_base);
+                       ms_hyperv.ghcb_base = NULL;
+                       goto clean_guest_os_id;
+               }
+
+               /* Hyper-V requires to write guest os id via ghcb in SNP IVM. */
+               hv_ghcb_msr_write(HV_X64_MSR_GUEST_OS_ID, guest_id);
        }
 
        rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
@@ -403,7 +452,8 @@ 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_vp_assist_page:
        kfree(hv_vp_assist_page);
@@ -431,6 +481,9 @@ void hyperv_cleanup(void)
         */
        hv_hypercall_pg = NULL;
 
+       if (ms_hyperv.ghcb_base)
+               free_percpu(ms_hyperv.ghcb_base);
+
        /* Reset the hypercall page */
        hypercall_msr.as_uint64 = 0;
        wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
@@ -506,3 +559,11 @@ 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..6627cfd2bfba 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);
diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
index c1ab6a6e72b5..4269f3174e58 100644
--- a/include/asm-generic/mshyperv.h
+++ b/include/asm-generic/mshyperv.h
@@ -36,6 +36,7 @@ struct ms_hyperv_info {
        u32 max_lp_index;
        u32 isolation_config_a;
        u32 isolation_config_b;
+       void  __percpu **ghcb_base;
 };
 extern struct ms_hyperv_info ms_hyperv;
 
@@ -237,6 +238,7 @@ 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