[PATCH V5 01/12] x86/hyperv: Initialize GHCB page in Isolation VM

Tianyu Lan
2021-09-14T13:39:30Z

From: Tianyu Lan <Tianyu.Lan@microsoft.com>

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@microsoft.com>
---
Change since v4:
* Fix typo comment

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..a7e922755ad1 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
+ * memory 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 e095c28d27ae..b09ade389040 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