[PATCH v2 12/15] mshv_vtl: Move VSM code page offset logic to x86 files

Naman Jain
2026-04-23T12:44:17Z

The VSM code page offset register (HV_REGISTER_VSM_CODE_PAGE_OFFSETS)
is x86 specific, its value configures the static call used to return
to VTL0 via the hypercall page. Move the register read from the common
mshv_vtl_get_vsm_regs() into the x86 mshv_vtl_return_call_init(),
which is the sole consumer of the offset.

Change mshv_vtl_return_call_init() from taking a u64 parameter
to taking no arguments, and rename mshv_vtl_get_vsm_regs() to
mshv_vtl_get_vsm_cap_reg() since it now only fetches
HV_REGISTER_VSM_CAPABILITIES.

No functional change on x86. This prepares the common driver code for
ARM64 where VSM code page offsets do not apply.

Signed-off-by: Naman Jain <namjain@linux.microsoft.com>
---
arch/x86/hyperv/hv_vtl.c | 19 +++++++++++++++++--
arch/x86/include/asm/mshyperv.h | 4 ++--
drivers/hv/mshv_vtl_main.c | 24 +++++++++++++-----------
3 files changed, 32 insertions(+), 15 deletions(-)

diff --git a/arch/x86/hyperv/hv_vtl.c b/arch/x86/hyperv/hv_vtl.c
index f3ffb6a7cb2d..7c10b34cf8a4 100644
--- a/arch/x86/hyperv/hv_vtl.c
+++ b/arch/x86/hyperv/hv_vtl.c
@@ -293,10 +293,25 @@ EXPORT_SYMBOL_GPL(hv_vtl_configure_reg_page);

DEFINE_STATIC_CALL_NULL(__mshv_vtl_return_hypercall, void (*)(void));

-void mshv_vtl_return_call_init(u64 vtl_return_offset)
+int mshv_vtl_return_call_init(void)
{
+ struct hv_register_assoc vsm_pg_offset_reg;
+ union hv_register_vsm_page_offsets offsets;
+ int ret;
+
+ vsm_pg_offset_reg.name = HV_REGISTER_VSM_CODE_PAGE_OFFSETS;
+
+ ret = hv_call_get_vp_registers(HV_VP_INDEX_SELF, HV_PARTITION_ID_SELF,
+ 1, input_vtl_zero, &vsm_pg_offset_reg);
+ if (ret)
+ return ret;
+
+ offsets.as_uint64 = vsm_pg_offset_reg.value.reg64;
+
static_call_update(__mshv_vtl_return_hypercall,
- (void *)((u8 *)hv_hypercall_pg + vtl_return_offset));
+ (void *)((u8 *)hv_hypercall_pg + offsets.vtl_return_offset));
+
+ return 0;
}
EXPORT_SYMBOL(mshv_vtl_return_call_init);

diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index b4d80c9a673a..b48f115c1292 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -286,14 +286,14 @@ struct mshv_vtl_cpu_context {
#ifdef CONFIG_HYPERV_VTL_MODE
void __init hv_vtl_init_platform(void);
int __init hv_vtl_early_init(void);
-void mshv_vtl_return_call_init(u64 vtl_return_offset);
+int mshv_vtl_return_call_init(void);
void mshv_vtl_return_hypercall(void);
void __mshv_vtl_return_call(struct mshv_vtl_cpu_context *vtl0);
int hv_vtl_get_set_reg(struct hv_register_assoc *regs, bool set, bool shared);
#else
static inline void __init hv_vtl_init_platform(void) {}
static inline int __init hv_vtl_early_init(void) { return 0; }
-static inline void mshv_vtl_return_call_init(u64 vtl_return_offset) {}
+static inline int mshv_vtl_return_call_init(void) { return 0; }
static inline void mshv_vtl_return_hypercall(void) {}
static inline void __mshv_vtl_return_call(struct mshv_vtl_cpu_context *vtl0) {}
#endif
diff --git a/drivers/hv/mshv_vtl_main.c b/drivers/hv/mshv_vtl_main.c
index 4c9ae65ad3e8..be498c9234fd 100644
--- a/drivers/hv/mshv_vtl_main.c
+++ b/drivers/hv/mshv_vtl_main.c
@@ -79,7 +79,6 @@ struct mshv_vtl {
};

static struct mutex mshv_vtl_poll_file_lock;
-static union hv_register_vsm_page_offsets mshv_vsm_page_offsets;
static union hv_register_vsm_capabilities mshv_vsm_capabilities;

static DEFINE_PER_CPU(struct mshv_vtl_poll_file, mshv_vtl_poll_file);
@@ -203,21 +202,19 @@ static void mshv_vtl_synic_enable_regs(unsigned int cpu)
/* VTL2 Host VSP SINT is (un)masked when the user mode requests that */
}

-static int mshv_vtl_get_vsm_regs(void)
+static int mshv_vtl_get_vsm_cap_reg(void)
{
- struct hv_register_assoc registers[2];
- int ret, count = 2;
+ struct hv_register_assoc vsm_capability_reg;
+ int ret;

- registers[0].name = HV_REGISTER_VSM_CODE_PAGE_OFFSETS;
- registers[1].name = HV_REGISTER_VSM_CAPABILITIES;
+ vsm_capability_reg.name = HV_REGISTER_VSM_CAPABILITIES;

ret = hv_call_get_vp_registers(HV_VP_INDEX_SELF, HV_PARTITION_ID_SELF,
- count, input_vtl_zero, registers);
+ 1, input_vtl_zero, &vsm_capability_reg);
if (ret)
return ret;

- mshv_vsm_page_offsets.as_uint64 = registers[0].value.reg64;
- mshv_vsm_capabilities.as_uint64 = registers[1].value.reg64;
+ mshv_vsm_capabilities.as_uint64 = vsm_capability_reg.value.reg64;

return ret;
}
@@ -1139,13 +1136,18 @@ static int __init mshv_vtl_init(void)
tasklet_init(&msg_dpc, mshv_vtl_sint_on_msg_dpc, 0);
init_waitqueue_head(&fd_wait_queue);

- if (mshv_vtl_get_vsm_regs()) {
+ if (mshv_vtl_get_vsm_cap_reg()) {
dev_emerg(dev, "Unable to get VSM capabilities !!\n");
ret = -ENODEV;
goto free_dev;
}

- mshv_vtl_return_call_init(mshv_vsm_page_offsets.vtl_return_offset);
+ ret = mshv_vtl_return_call_init();
+ if (ret) {
+ dev_err(dev, "mshv_vtl_return_call_init failed: %d\n", ret);
+ goto free_dev;
+ }
+
ret = hv_vtl_setup_synic();
if (ret)
goto free_dev;