[PATCH 6/9] x86/hyperv: Introduce a global variable hyperv_paravisor_present

Dexuan Cui
2023-08-11T22:20:18Z

The new variable hyperv_paravisor_present is set only when the VM
is a SNP/TDX with the paravisor running: see ms_hyperv_init_platform().

In many places, hyperv_paravisor_present can replace
ms_hyperv.paravisor_present, and it's also used to replace
hv_isolation_type_snp() in drivers/hv/hv.c.

Call hv_vtom_init() when it's a VBS VM or when hyperv_paravisor_present
is true (i.e. the VM is a SNP/TDX VM with the paravisor).

Enhance hv_vtom_init() for a TDX VM with the paravisor.

The biggest motive to introduce hyperv_paravisor_present is that we
can not use ms_hyperv.paravisor_present in arch/x86/include/asm/mshyperv.h:
that would introduce a complicated header file dependency issue.

In arch/x86/include/asm/mshyperv.h, _hv_do_fast_hypercall8()
is changed to specially handle HVCALL_SIGNAL_EVENT for a TDX VM with the
paravisor, because such a VM must use TDX GHCI (see hv_tdx_hypercall())
for this hypercall. See vmbus_set_event() -> hv_do_fast_hypercall8() ->
_hv_do_fast_hypercall8() -> hv_tdx_hypercall().

In hv_common_cpu_init(), don't decrypt the hyperv_pcpu_input_arg
for a TDX VM with the paravisor, just like we don't decrypt the page
for a SNP VM with the paravisor.

Signed-off-by: Dexuan Cui <decui@microsoft.com>
---
arch/x86/hyperv/hv_apic.c | 4 ++--
arch/x86/hyperv/hv_init.c | 4 ++--
arch/x86/hyperv/ivm.c | 20 ++++++++++++++++++--
arch/x86/include/asm/mshyperv.h | 9 ++++++---
arch/x86/kernel/cpu/mshyperv.c | 13 ++++++++++---
drivers/hv/connection.c | 2 +-
drivers/hv/hv.c | 12 ++++++------
drivers/hv/hv_common.c | 6 +++++-
include/asm-generic/mshyperv.h | 1 +
9 files changed, 51 insertions(+), 20 deletions(-)

diff --git a/arch/x86/hyperv/hv_apic.c b/arch/x86/hyperv/hv_apic.c
index cb7429046d18d..8958836500d01 100644
--- a/arch/x86/hyperv/hv_apic.c
+++ b/arch/x86/hyperv/hv_apic.c
@@ -179,7 +179,7 @@ static bool __send_ipi_mask(const struct cpumask *mask, int vector,

/* A fully enlightened TDX VM uses GHCI rather than hv_hypercall_pg. */
if (!hv_hypercall_pg) {
- if (ms_hyperv.paravisor_present || !hv_isolation_type_tdx())
+ if (hyperv_paravisor_present || !hv_isolation_type_tdx())
return false;
}

@@ -239,7 +239,7 @@ static bool __send_ipi_one(int cpu, int vector)

/* A fully enlightened TDX VM uses GHCI rather than hv_hypercall_pg. */
if (!hv_hypercall_pg) {
- if (ms_hyperv.paravisor_present || !hv_isolation_type_tdx())
+ if (hyperv_paravisor_present || !hv_isolation_type_tdx())
return false;
}

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 4bcd0a6f94760..e67e2430fba35 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -663,8 +663,8 @@ bool hv_is_hyperv_initialized(void)
if (x86_hyper_type != X86_HYPER_MS_HYPERV)
return false;

- /* A TDX guest uses the GHCI call rather than hv_hypercall_pg. */
- if (hv_isolation_type_tdx())
+ /* A TDX VM with no paravisor uses TDX GHCI call rather than hv_hypercall_pg */
+ if (hv_isolation_type_tdx() && !hyperv_paravisor_present)
return true;
/*
* Verify that earlier initialization succeeded by checking
diff --git a/arch/x86/hyperv/ivm.c b/arch/x86/hyperv/ivm.c
index 5792cddea4914..0d54bc8b06b4a 100644
--- a/arch/x86/hyperv/ivm.c
+++ b/arch/x86/hyperv/ivm.c
@@ -459,13 +459,29 @@ int hv_snp_boot_ap(int cpu, unsigned long start_ip)

void __init hv_vtom_init(void)
{
+ enum hv_isolation_type type = hv_get_isolation_type();
/*
* By design, a VM using vTOM doesn't see the SEV setting,
* so SEV initialization is bypassed and sev_status isn't set.
* Set it here to indicate a vTOM VM.
*/
- sev_status = MSR_AMD64_SNP_VTOM;
- cc_vendor = CC_VENDOR_AMD;
+ switch (type) {
+ case HV_ISOLATION_TYPE_VBS:
+ fallthrough;
+
+ case HV_ISOLATION_TYPE_SNP:
+ sev_status = MSR_AMD64_SNP_VTOM;
+ cc_vendor = CC_VENDOR_AMD;
+ break;
+
+ case HV_ISOLATION_TYPE_TDX:
+ cc_vendor = CC_VENDOR_INTEL;
+ break;
+
+ default:
+ panic("hv_vtom_init: unsupported isolation type %d\n", type);
+ }
+
cc_set_mask(ms_hyperv.shared_gpa_boundary);
physical_mask &= ms_hyperv.shared_gpa_boundary - 1;

diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index 4c68564a165e5..9fa31dce69727 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -42,6 +42,7 @@ static inline unsigned char hv_get_nmi_reason(void)

#if IS_ENABLED(CONFIG_HYPERV)
extern int hyperv_init_cpuhp;
+extern bool hyperv_paravisor_present;

extern void *hv_hypercall_pg;

@@ -74,7 +75,7 @@ static inline u64 hv_do_hypercall(u64 control, void *input, void *output)
u64 hv_status;

#ifdef CONFIG_X86_64
- if (hv_isolation_type_tdx())
+ if (hv_isolation_type_tdx() && !hyperv_paravisor_present)
return hv_tdx_hypercall(control,
cc_mkdec(input_address),
cc_mkdec(output_address));
@@ -121,7 +122,9 @@ static inline u64 _hv_do_fast_hypercall8(u64 control, u64 input1)
u64 hv_status;

#ifdef CONFIG_X86_64
- if (hv_isolation_type_tdx())
+ if (hv_isolation_type_tdx() &&
+ (!hyperv_paravisor_present ||
+ control == (HVCALL_SIGNAL_EVENT | HV_HYPERCALL_FAST_BIT)))
return hv_tdx_hypercall(control, input1, 0);

{
@@ -170,7 +173,7 @@ static inline u64 _hv_do_fast_hypercall16(u64 control, u64 input1, u64 input2)
u64 hv_status;

#ifdef CONFIG_X86_64
- if (hv_isolation_type_tdx())
+ if (hv_isolation_type_tdx() && !hyperv_paravisor_present)
return hv_tdx_hypercall(control, input1, input2);

{
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index b4214e37e9124..ddcc62185e4ae 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -40,6 +40,12 @@ bool hv_root_partition;
bool hv_nested;
struct ms_hyperv_info ms_hyperv;

+/*
+ * Used in modules via hv_do_hypercall(): see arch/x86/include/asm/mshyperv.h.
+ * Exported in drivers/hv/hv_common.c to not break the ARM64 build.
+ */
+bool hyperv_paravisor_present __ro_after_init;
+
#if IS_ENABLED(CONFIG_HYPERV)
static inline unsigned int hv_get_nested_reg(unsigned int reg)
{
@@ -430,6 +436,8 @@ static void __init ms_hyperv_init_platform(void)
ms_hyperv.shared_gpa_boundary =
BIT_ULL(ms_hyperv.shared_gpa_boundary_bits);

+ hyperv_paravisor_present = !!ms_hyperv.paravisor_present;
+
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);

@@ -444,7 +452,7 @@ static void __init ms_hyperv_init_platform(void)
/* A TDX VM must use x2APIC and doesn't use lazy EOI. */
ms_hyperv.hints &= ~HV_X64_APIC_ACCESS_RECOMMENDED;

- if (!ms_hyperv.paravisor_present) {
+ if (!hyperv_paravisor_present) {
/*
* The ms_hyperv.shared_gpa_boundary_active in
* a fully enlightened TDX VM is 0, but the GPAs
@@ -535,8 +543,7 @@ static void __init ms_hyperv_init_platform(void)

#if IS_ENABLED(CONFIG_HYPERV)
if ((hv_get_isolation_type() == HV_ISOLATION_TYPE_VBS) ||
- ((hv_get_isolation_type() == HV_ISOLATION_TYPE_SNP) &&
- ms_hyperv.paravisor_present))
+ hyperv_paravisor_present)
hv_vtom_init();
/*
* Setup the hook to get control post apic initialization.
diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
index 02b54f85dc607..7f64fc942323b 100644
--- a/drivers/hv/connection.c
+++ b/drivers/hv/connection.c
@@ -484,7 +484,7 @@ void vmbus_set_event(struct vmbus_channel *channel)

++channel->sig_events;

- if (hv_isolation_type_snp())
+ if (hv_isolation_type_snp() && hyperv_paravisor_present)
hv_ghcb_hypercall(HVCALL_SIGNAL_EVENT, &channel->sig_event,
NULL, sizeof(channel->sig_event));
else
diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index 28bbb354324d6..20bc44923e4f0 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -109,7 +109,7 @@ int hv_synic_alloc(void)
* Synic message and event pages are allocated by paravisor.
* Skip these pages allocation here.
*/
- if (!hv_isolation_type_snp() && !hv_root_partition) {
+ if (!hyperv_paravisor_present && !hv_root_partition) {
hv_cpu->synic_message_page =
(void *)get_zeroed_page(GFP_ATOMIC);
if (hv_cpu->synic_message_page == NULL) {
@@ -128,7 +128,7 @@ int hv_synic_alloc(void)
}
}

- if (!ms_hyperv.paravisor_present &&
+ if (!hyperv_paravisor_present &&
(hv_isolation_type_en_snp() || hv_isolation_type_tdx())) {
ret = set_memory_decrypted((unsigned long)
hv_cpu->synic_message_page, 1);
@@ -226,7 +226,7 @@ void hv_synic_enable_regs(unsigned int cpu)
simp.as_uint64 = hv_get_register(HV_REGISTER_SIMP);
simp.simp_enabled = 1;

- if (hv_isolation_type_snp() || hv_root_partition) {
+ if (hyperv_paravisor_present || hv_root_partition) {
/* Mask out vTOM bit. ioremap_cache() maps decrypted */
u64 base = (simp.base_simp_gpa << HV_HYP_PAGE_SHIFT) &
~ms_hyperv.shared_gpa_boundary;
@@ -249,7 +249,7 @@ void hv_synic_enable_regs(unsigned int cpu)
siefp.as_uint64 = hv_get_register(HV_REGISTER_SIEFP);
siefp.siefp_enabled = 1;

- if (hv_isolation_type_snp() || hv_root_partition) {
+ if (hyperv_paravisor_present || hv_root_partition) {
/* Mask out vTOM bit. ioremap_cache() maps decrypted */
u64 base = (siefp.base_siefp_gpa << HV_HYP_PAGE_SHIFT) &
~ms_hyperv.shared_gpa_boundary;
@@ -336,7 +336,7 @@ void hv_synic_disable_regs(unsigned int cpu)
* addresses.
*/
simp.simp_enabled = 0;
- if (hv_isolation_type_snp() || hv_root_partition) {
+ if (hyperv_paravisor_present || hv_root_partition) {
iounmap(hv_cpu->synic_message_page);
hv_cpu->synic_message_page = NULL;
} else {
@@ -348,7 +348,7 @@ void hv_synic_disable_regs(unsigned int cpu)
siefp.as_uint64 = hv_get_register(HV_REGISTER_SIEFP);
siefp.siefp_enabled = 0;

- if (hv_isolation_type_snp() || hv_root_partition) {
+ if (hyperv_paravisor_present || hv_root_partition) {
iounmap(hv_cpu->synic_event_page);
hv_cpu->synic_event_page = NULL;
} else {
diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
index 4c858e1636da7..c0b0ac44ffa3c 100644
--- a/drivers/hv/hv_common.c
+++ b/drivers/hv/hv_common.c
@@ -40,6 +40,9 @@
bool __weak hv_root_partition;
EXPORT_SYMBOL_GPL(hv_root_partition);

+bool __weak hyperv_paravisor_present;
+EXPORT_SYMBOL_GPL(hyperv_paravisor_present);
+
bool __weak hv_nested;
EXPORT_SYMBOL_GPL(hv_nested);

@@ -382,7 +385,8 @@ int hv_common_cpu_init(unsigned int cpu)
*outputarg = (char *)mem + HV_HYP_PAGE_SIZE;
}

- if (hv_isolation_type_en_snp() || hv_isolation_type_tdx()) {
+ if (!hyperv_paravisor_present &&
+ (hv_isolation_type_en_snp() || hv_isolation_type_tdx())) {
ret = set_memory_decrypted((unsigned long)mem, pgcount);
if (ret) {
/* It may be unsafe to free 'mem' */
diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
index 30fa75facd784..a6e4f38222c81 100644
--- a/include/asm-generic/mshyperv.h
+++ b/include/asm-generic/mshyperv.h
@@ -176,6 +176,7 @@ extern int vmbus_interrupt;
extern int vmbus_irq;

extern bool hv_root_partition;
+extern bool hyperv_paravisor_present;

#if IS_ENABLED(CONFIG_HYPERV)
/*
--
2.25.1