Re: [RFC PATCH V3 10/16] x86/hyperv: Add smp support for sev-snp guest

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On 1/21/23 20:46, Tianyu Lan wrote:
From: Tianyu Lan <tiala@xxxxxxxxxxxxx>

The wakeup_secondary_cpu callback was populated with wakeup_
cpu_via_vmgexit() which doesn't work for Hyper-V. Override it

An explanation as to why is doesn't work would be nice here.

with Hyper-V specific hook which uses HVCALL_START_VIRTUAL_
PROCESSOR hvcall to start AP with vmsa data structure.

Signed-off-by: Tianyu Lan <tiala@xxxxxxxxxxxxx>
---
Change since RFC v2:
        * Add helper function to initialize segment
        * Fix some coding style
---
  arch/x86/include/asm/mshyperv.h   |   2 +
  arch/x86/include/asm/sev.h        |  13 ++++
  arch/x86/include/asm/svm.h        |  47 +++++++++++++
  arch/x86/kernel/cpu/mshyperv.c    | 112 ++++++++++++++++++++++++++++--
  include/asm-generic/hyperv-tlfs.h |  19 +++++
  5 files changed, 189 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index 7266d71d30d6..c69051eec0e1 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -203,6 +203,8 @@ struct irq_domain *hv_create_pci_msi_domain(void);
  int hv_map_ioapic_interrupt(int ioapic_id, bool level, int vcpu, int vector,
  		struct hv_interrupt_entry *entry);
  int hv_unmap_ioapic_interrupt(int ioapic_id, struct hv_interrupt_entry *entry);
+int hv_set_mem_host_visibility(unsigned long addr, int numpages, bool visible);
+int hv_snp_boot_ap(int cpu, unsigned long start_ip);
#ifdef CONFIG_AMD_MEM_ENCRYPT
  void hv_ghcb_msr_write(u64 msr, u64 value);
diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index ebc271bb6d8e..e34aaf730220 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -86,6 +86,19 @@ extern bool handle_vc_boot_ghcb(struct pt_regs *regs);
#define RMPADJUST_VMSA_PAGE_BIT BIT(16) +union sev_rmp_adjust {
+	u64 as_uint64;
+	struct {
+		unsigned long target_vmpl : 8;
+		unsigned long enable_read : 1;
+		unsigned long enable_write : 1;
+		unsigned long enable_user_execute : 1;
+		unsigned long enable_kernel_execute : 1;
+		unsigned long reserved1 : 4;
+		unsigned long vmsa : 1;
+	};
+};
+
  /* SNP Guest message request */
  struct snp_req_data {
  	unsigned long req_gpa;
diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h
index cb1ee53ad3b1..f8b321a11ee4 100644
--- a/arch/x86/include/asm/svm.h
+++ b/arch/x86/include/asm/svm.h
@@ -336,6 +336,53 @@ struct vmcb_save_area {

Please don't update the vmcb_save_area, you should be using/updating the sev_es_save_area structure for SNP.

  	u64 last_excp_to;
  	u8 reserved_0x298[72];
  	u32 spec_ctrl;		/* Guest version of SPEC_CTRL at 0x2E0 */
+	u8 reserved_7b[4];
+	u32 pkru;
+	u8 reserved_7a[20];
+	u64 reserved_8;		/* rax already available at 0x01f8 */
+	u64 rcx;
+	u64 rdx;
+	u64 rbx;
+	u64 reserved_9;		/* rsp already available at 0x01d8 */
+	u64 rbp;
+	u64 rsi;
+	u64 rdi;
+	u64 r8;
+	u64 r9;
+	u64 r10;
+	u64 r11;
+	u64 r12;
+	u64 r13;
+	u64 r14;
+	u64 r15;
+	u8 reserved_10[16];
+	u64 sw_exit_code;
+	u64 sw_exit_info_1;
+	u64 sw_exit_info_2;
+	u64 sw_scratch;
+	union {
+		u64 sev_features;
+		struct {
+			u64 sev_feature_snp			: 1;
+			u64 sev_feature_vtom			: 1;
+			u64 sev_feature_reflectvc		: 1;
+			u64 sev_feature_restrict_injection	: 1;
+			u64 sev_feature_alternate_injection	: 1;
+			u64 sev_feature_full_debug		: 1;
+			u64 sev_feature_reserved1		: 1;
+			u64 sev_feature_snpbtb_isolation	: 1;
+			u64 sev_feature_resrved2		: 56;

For the bits definition, use:

			u64 sev_feature_snp			: 1,
			    sev_feature_vtom			: 1,
			    sev_feature_reflectvc		: 1,
			    ...

Thanks,
Tom

+		};
+	};
+	u64 vintr_ctrl;
+	u64 guest_error_code;
+	u64 virtual_tom;
+	u64 tlb_id;
+	u64 pcpu_id;
+	u64 event_inject;
+	u64 xcr0;
+	u8 valid_bitmap[16];
+	u64 x87_state_gpa;
  } __packed;
/* Save area definition for SEV-ES and SEV-SNP guests */
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 197c8f2ec4eb..9d547751a1a7 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -39,6 +39,13 @@
  #include <asm/realmode.h>
  #include <asm/e820/api.h>
+/*
+ * DEFAULT INIT GPAT and SEGMENT LIMIT value in struct VMSA
+ * to start AP in enlightened SEV guest.
+ */
+#define HV_AP_INIT_GPAT_DEFAULT		0x0007040600070406ULL
+#define HV_AP_SEGMENT_LIMIT		0xffffffff
+
  /* Is Linux running as the root partition? */
  bool hv_root_partition;
  struct ms_hyperv_info ms_hyperv;
@@ -230,6 +237,94 @@ static void __init hv_smp_prepare_boot_cpu(void)
  #endif
  }
+static u8 ap_start_input_arg[PAGE_SIZE] __bss_decrypted __aligned(PAGE_SIZE);
+static u8 ap_start_stack[PAGE_SIZE] __aligned(PAGE_SIZE);
+
+#define hv_populate_vmcb_seg(seg, gdtr_base)			\
+do {								\
+	if (seg.selector) {					\
+		seg.base = 0;					\
+		seg.limit = HV_AP_SEGMENT_LIMIT;		\
+		seg.attrib = *(u16 *)(gdtr_base + seg.selector + 5);	\
+		seg.attrib = (seg.attrib & 0xFF) | ((seg.attrib >> 4) & 0xF00); \
+	}							\
+} while (0)							\
+
+int hv_snp_boot_ap(int cpu, unsigned long start_ip)
+{
+	struct vmcb_save_area *vmsa = (struct vmcb_save_area *)
+		__get_free_page(GFP_KERNEL | __GFP_ZERO);
+	struct desc_ptr gdtr;
+	u64 ret, retry = 5;
+	struct hv_start_virtual_processor_input *start_vp_input;
+	union sev_rmp_adjust rmp_adjust;
+	unsigned long flags;
+
+	native_store_gdt(&gdtr);
+
+	vmsa->gdtr.base = gdtr.address;
+	vmsa->gdtr.limit = gdtr.size;
+
+	asm volatile("movl %%es, %%eax;" : "=a" (vmsa->es.selector));
+	hv_populate_vmcb_seg(vmsa->es, vmsa->gdtr.base);
+
+	asm volatile("movl %%cs, %%eax;" : "=a" (vmsa->cs.selector));
+	hv_populate_vmcb_seg(vmsa->cs, vmsa->gdtr.base);
+
+	asm volatile("movl %%ss, %%eax;" : "=a" (vmsa->ss.selector));
+	hv_populate_vmcb_seg(vmsa->ss, vmsa->gdtr.base);
+
+	asm volatile("movl %%ds, %%eax;" : "=a" (vmsa->ds.selector));
+	hv_populate_vmcb_seg(vmsa->ds, vmsa->gdtr.base);
+
+	vmsa->efer = native_read_msr(MSR_EFER);
+
+	asm volatile("movq %%cr4, %%rax;" : "=a" (vmsa->cr4));
+	asm volatile("movq %%cr3, %%rax;" : "=a" (vmsa->cr3));
+	asm volatile("movq %%cr0, %%rax;" : "=a" (vmsa->cr0));
+
+	vmsa->xcr0 = 1;
+	vmsa->g_pat = HV_AP_INIT_GPAT_DEFAULT;
+	vmsa->rip = (u64)secondary_startup_64_no_verify;
+	vmsa->rsp = (u64)&ap_start_stack[PAGE_SIZE];
+
+	vmsa->sev_feature_snp = 1;
+	vmsa->sev_feature_restrict_injection = 1;
+
+	rmp_adjust.as_uint64 = 0;
+	rmp_adjust.target_vmpl = 1;
+	rmp_adjust.vmsa = 1;
+	ret = rmpadjust((unsigned long)vmsa, RMP_PG_SIZE_4K,
+			rmp_adjust.as_uint64);
+	if (ret != 0) {
+		pr_err("RMPADJUST(%llx) failed: %llx\n", (u64)vmsa, ret);
+		return ret;
+	}
+
+	local_irq_save(flags);
+	start_vp_input =
+		(struct hv_start_virtual_processor_input *)ap_start_input_arg;
+	memset(start_vp_input, 0, sizeof(*start_vp_input));
+	start_vp_input->partitionid = -1;
+	start_vp_input->vpindex = cpu;
+	start_vp_input->targetvtl = ms_hyperv.vtl;
+	*(u64 *)&start_vp_input->context[0] = __pa(vmsa) | 1;
+
+	do {
+		ret = hv_do_hypercall(HVCALL_START_VIRTUAL_PROCESSOR,
+				      start_vp_input, NULL);
+	} while (hv_result(ret) == HV_STATUS_TIME_OUT && retry--);
+
+	if (!hv_result_success(ret)) {
+		pr_err("HvCallStartVirtualProcessor failed: %llx\n", ret);
+		goto done;
+	}
+
+done:
+	local_irq_restore(flags);
+	return ret;
+}
+
  static void __init hv_smp_prepare_cpus(unsigned int max_cpus)
  {
  #ifdef CONFIG_X86_64
@@ -239,6 +334,16 @@ static void __init hv_smp_prepare_cpus(unsigned int max_cpus)
native_smp_prepare_cpus(max_cpus); + /*
+	 *  Override wakeup_secondary_cpu callback for SEV-SNP
+	 *  enlightened guest.
+	 */
+	if (hv_isolation_type_en_snp())
+		apic->wakeup_secondary_cpu = hv_snp_boot_ap;
+
+	if (!hv_root_partition)
+		return;
+
  #ifdef CONFIG_X86_64
  	for_each_present_cpu(i) {
  		if (i == 0)
@@ -475,8 +580,7 @@ static void __init ms_hyperv_init_platform(void)
# ifdef CONFIG_SMP
  	smp_ops.smp_prepare_boot_cpu = hv_smp_prepare_boot_cpu;
-	if (hv_root_partition)
-		smp_ops.smp_prepare_cpus = hv_smp_prepare_cpus;
+	smp_ops.smp_prepare_cpus = hv_smp_prepare_cpus;
  # endif
/*
@@ -501,7 +605,7 @@ static void __init ms_hyperv_init_platform(void)
  	if (!(ms_hyperv.features & HV_ACCESS_TSC_INVARIANT))
  		mark_tsc_unstable("running on Hyper-V");
- if (isolation_type_en_snp()) {
+	if (hv_isolation_type_en_snp()) {
  		/*
  		 * Hyper-V enlightened snp guest boots kernel
  		 * directly without bootloader and so roms,
@@ -511,7 +615,7 @@ static void __init ms_hyperv_init_platform(void)
  		x86_platform.legacy.rtc = 0;
  		x86_platform.set_wallclock = set_rtc_noop;
  		x86_platform.get_wallclock = get_rtc_noop;
-		x86_platform.legacy.reserve_bios_regions = x86_init_noop;
+		x86_platform.legacy.reserve_bios_regions = 0;
  		x86_init.resources.probe_roms = x86_init_noop;
  		x86_init.resources.reserve_resources = x86_init_noop;
  		x86_init.mpparse.find_smp_config = x86_init_noop;
diff --git a/include/asm-generic/hyperv-tlfs.h b/include/asm-generic/hyperv-tlfs.h
index c1cc3ec36ad5..3d7c67be9f56 100644
--- a/include/asm-generic/hyperv-tlfs.h
+++ b/include/asm-generic/hyperv-tlfs.h
@@ -148,6 +148,7 @@ union hv_reference_tsc_msr {
  #define HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST	0x0003
  #define HVCALL_NOTIFY_LONG_SPIN_WAIT		0x0008
  #define HVCALL_SEND_IPI				0x000b
+#define HVCALL_ENABLE_VP_VTL			0x000f
  #define HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE_EX	0x0013
  #define HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST_EX	0x0014
  #define HVCALL_SEND_IPI_EX			0x0015
@@ -165,6 +166,7 @@ union hv_reference_tsc_msr {
  #define HVCALL_MAP_DEVICE_INTERRUPT		0x007c
  #define HVCALL_UNMAP_DEVICE_INTERRUPT		0x007d
  #define HVCALL_RETARGET_INTERRUPT		0x007e
+#define HVCALL_START_VIRTUAL_PROCESSOR		0x0099
  #define HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_SPACE 0x00af
  #define HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_LIST 0x00b0
  #define HVCALL_MODIFY_SPARSE_GPA_PAGE_HOST_VISIBILITY 0x00db
@@ -219,6 +221,7 @@ enum HV_GENERIC_SET_FORMAT {
  #define HV_STATUS_INVALID_PORT_ID		17
  #define HV_STATUS_INVALID_CONNECTION_ID		18
  #define HV_STATUS_INSUFFICIENT_BUFFERS		19
+#define HV_STATUS_TIME_OUT                     0x78
/*
   * The Hyper-V TimeRefCount register and the TSC
@@ -778,6 +781,22 @@ struct hv_input_unmap_device_interrupt {
  	struct hv_interrupt_entry interrupt_entry;
  } __packed;
+struct hv_enable_vp_vtl_input {
+	u64 partitionid;
+	u32 vpindex;
+	u8 targetvtl;
+	u8 padding[3];
+	u8 context[0xe0];
+} __packed;
+
+struct hv_start_virtual_processor_input {
+	u64 partitionid;
+	u32 vpindex;
+	u8 targetvtl;
+	u8 padding[3];
+	u8 context[0xe0];
+} __packed;
+
  #define HV_SOURCE_SHADOW_NONE               0x0
  #define HV_SOURCE_SHADOW_BRIDGE_BUS_RANGE   0x1



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