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

From: Tom Lendacky
Date: Mon Jan 23 2023 - 10:30:35 EST

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