[PATCH v3 02/10] x86/hyperv: Support hypercalls for fully enlightened TDX guests

Dexuan Cui
2023-08-24T08:11:00Z

A fully enlightened TDX guest on Hyper-V (i.e. without the paravisor) only
uses the GHCI call rather than hv_hypercall_pg. Do not initialize
hypercall_pg for such a guest.

In hv_common_cpu_init(), the hyperv_pcpu_input_arg page needs to be
decrypted in such a guest.

Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Reviewed-by: Tianyu Lan <tiala@microsoft.com>
Signed-off-by: Dexuan Cui <decui@microsoft.com>
---

Changes in v2:
Included asm/coco.h in arch/x86/include/asm/mshyperv.h to avoid a
gcc warning: "implicit declaration of cc_mkdec"

Changes in v3:
Added Tianyu's Reviewed-by.
Removed the cc_mkdec() from hv_do_hypercall(). This is no longer
needed on generally available Hyper-V.
Removed the inclusion of coco.h

arch/x86/hyperv/hv_init.c | 8 ++++++++
arch/x86/hyperv/ivm.c | 17 +++++++++++++++++
arch/x86/include/asm/mshyperv.h | 14 ++++++++++++++
drivers/hv/hv_common.c | 10 ++++++++--
include/asm-generic/mshyperv.h | 1 +
5 files changed, 48 insertions(+), 2 deletions(-)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index bcfbcda8b050..255e02ec467e 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -476,6 +476,10 @@ void __init hyperv_init(void)
/* 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);

+ /* A TDX guest uses the GHCI call rather than hv_hypercall_pg. */
+ if (hv_isolation_type_tdx())
+ goto skip_hypercall_pg_init;
+
hv_hypercall_pg = __vmalloc_node_range(PAGE_SIZE, 1, VMALLOC_START,
VMALLOC_END, GFP_KERNEL, PAGE_KERNEL_ROX,
VM_FLUSH_RESET_PERMS, NUMA_NO_NODE,
@@ -515,6 +519,7 @@ void __init hyperv_init(void)
wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
}

+skip_hypercall_pg_init:
/*
* hyperv_init() is called before LAPIC is initialized: see
* apic_intr_mode_init() -> x86_platform.apic_post_init() and
@@ -642,6 +647,9 @@ 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())
+ return true;
/*
* Verify that earlier initialization succeeded by checking
* that the hypercall page is setup
diff --git a/arch/x86/hyperv/ivm.c b/arch/x86/hyperv/ivm.c
index afdae1a8a117..6c7598d9e68a 100644
--- a/arch/x86/hyperv/ivm.c
+++ b/arch/x86/hyperv/ivm.c
@@ -571,3 +571,20 @@ bool hv_isolation_type_tdx(void)
{
return static_branch_unlikely(&isolation_type_tdx);
}
+
+#ifdef CONFIG_INTEL_TDX_GUEST
+
+u64 hv_tdx_hypercall(u64 control, u64 param1, u64 param2)
+{
+ struct tdx_hypercall_args args = { };
+
+ args.r10 = control;
+ args.rdx = param1;
+ args.r8 = param2;
+
+ (void)__tdx_hypercall_ret(&args);
+
+ return args.r11;
+}
+
+#endif
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index 3feb4e36851e..6a9e00c4730b 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -51,6 +51,7 @@ extern union hv_ghcb * __percpu *hv_ghcb_pg;

extern bool hv_isolation_type_en_snp(void);
bool hv_isolation_type_tdx(void);
+u64 hv_tdx_hypercall(u64 control, u64 param1, u64 param2);

/*
* DEFAULT INIT GPAT and SEGMENT LIMIT value in struct VMSA
@@ -63,6 +64,10 @@ 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);

+/*
+ * If the hypercall involves no input or output parameters, the hypervisor
+ * ignores the corresponding GPA pointer.
+ */
static inline u64 hv_do_hypercall(u64 control, void *input, void *output)
{
u64 input_address = input ? virt_to_phys(input) : 0;
@@ -70,6 +75,9 @@ static inline u64 hv_do_hypercall(u64 control, void *input, void *output)
u64 hv_status;

#ifdef CONFIG_X86_64
+ if (hv_isolation_type_tdx())
+ return hv_tdx_hypercall(control, input_address, output_address);
+
if (hv_isolation_type_en_snp()) {
__asm__ __volatile__("mov %4, %%r8\n"
"vmmcall"
@@ -123,6 +131,9 @@ static inline u64 _hv_do_fast_hypercall8(u64 control, u64 input1)
u64 hv_status;

#ifdef CONFIG_X86_64
+ if (hv_isolation_type_tdx())
+ return hv_tdx_hypercall(control, input1, 0);
+
if (hv_isolation_type_en_snp()) {
__asm__ __volatile__(
"vmmcall"
@@ -174,6 +185,9 @@ 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())
+ return hv_tdx_hypercall(control, input1, input2);
+
if (hv_isolation_type_en_snp()) {
__asm__ __volatile__("mov %4, %%r8\n"
"vmmcall"
diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
index da3307533f4d..897bbb96f411 100644
--- a/drivers/hv/hv_common.c
+++ b/drivers/hv/hv_common.c
@@ -381,10 +381,10 @@ int hv_common_cpu_init(unsigned int cpu)
*outputarg = (char *)(*inputarg) + HV_HYP_PAGE_SIZE;
}

- if (hv_isolation_type_en_snp()) {
+ if (hv_isolation_type_en_snp() || hv_isolation_type_tdx()) {
ret = set_memory_decrypted((unsigned long)*inputarg, pgcount);
if (ret) {
- kfree(*inputarg);
+ /* It may be unsafe to free *inputarg */
*inputarg = NULL;
return ret;
}
@@ -567,3 +567,9 @@ u64 __weak hv_ghcb_hypercall(u64 control, void *input, void *output, u32 input_s
return HV_STATUS_INVALID_PARAMETER;
}
EXPORT_SYMBOL_GPL(hv_ghcb_hypercall);
+
+u64 __weak hv_tdx_hypercall(u64 control, u64 param1, u64 param2)
+{
+ return HV_STATUS_INVALID_PARAMETER;
+}
+EXPORT_SYMBOL_GPL(hv_tdx_hypercall);
diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
index 82eba2d5fc4c..f577eff58ea0 100644
--- a/include/asm-generic/mshyperv.h
+++ b/include/asm-generic/mshyperv.h
@@ -283,6 +283,7 @@ enum hv_isolation_type hv_get_isolation_type(void);
bool hv_is_isolation_supported(void);
bool hv_isolation_type_snp(void);
u64 hv_ghcb_hypercall(u64 control, void *input, void *output, u32 input_size);
+u64 hv_tdx_hypercall(u64 control, u64 param1, u64 param2);
void hyperv_cleanup(void);
bool hv_query_ext_cap(u64 cap_query);
void hv_setup_dma_ops(struct device *dev, bool coherent);
--
2.25.1