[Resend RFC PATCH V4 01/13] x86/HV: Initialize GHCB page in Isolation VM

Tianyu Lan
2021-07-07T15:46:59Z

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@microsoft.com>
---
arch/x86/hyperv/hv_init.c | 64 ++++++++++++++++++++++++++++++---
arch/x86/include/asm/mshyperv.h | 2 ++
include/asm-generic/mshyperv.h | 2 ++
3 files changed, 64 insertions(+), 4 deletions(-)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index b756b2866deb..e058f72eeee5 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>
@@ -54,6 +55,26 @@ EXPORT_SYMBOL_GPL(hyperv_pcpu_output_arg);
u32 hv_max_vp_index;
EXPORT_SYMBOL_GPL(hv_max_vp_index);

+static int hyperv_init_ghcb(void)
+{
+ u64 ghcb_gpa;
+ void *ghcb_va;
+ void **ghcb_base;
+
+ if (!ms_hyperv.ghcb_base)
+ return -EINVAL;
+
+ 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)
{
u64 msr_vp_index;
@@ -106,6 +127,8 @@ static int hv_cpu_init(unsigned int cpu)
wrmsrl(HV_X64_MSR_VP_ASSIST_PAGE, val);
}

+ hyperv_init_ghcb();
+
return 0;
}

@@ -201,6 +224,7 @@ static int hv_cpu_die(unsigned int cpu)
unsigned long flags;
void **input_arg;
void *pg;
+ void **ghcb_va = NULL;

local_irq_save(flags);
input_arg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
@@ -214,6 +238,13 @@ static int hv_cpu_die(unsigned int cpu)
*output_arg = 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;
+ }
+
local_irq_restore(flags);

free_pages((unsigned long)pg, hv_root_partition ? 1 : 0);
@@ -410,9 +441,22 @@ 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);
@@ -473,7 +517,8 @@ 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);
@@ -502,6 +547,9 @@ 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);
@@ -586,6 +634,14 @@ bool hv_is_isolation_supported(void)
}
EXPORT_SYMBOL_GPL(hv_is_isolation_supported);

+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);
+
/* Bit mask of the extended capability to query: see HV_EXT_CAPABILITY_xxx */
bool hv_query_ext_cap(u64 cap_query)
{
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index 67ff0d637e55..aeacca7c4da8 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 9a000ba2bb75..3ae56a29594f 100644
--- a/include/asm-generic/mshyperv.h
+++ b/include/asm-generic/mshyperv.h
@@ -35,6 +35,7 @@ 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;

@@ -224,6 +225,7 @@ 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