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

From: Michael Kelley (LINUX)
Date: Tue Jan 31 2023 - 13:35:09 EST

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From: Tianyu Lan <ltykernel@xxxxxxxxx> Sent: Saturday, January 21, 2023 6:46 PM
>
> The wakeup_secondary_cpu callback was populated with wakeup_
> cpu_via_vmgexit() which doesn't work for Hyper-V. Override it
> 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 {
> 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;
> + };
> + };
> + 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

If these values are defined by Hyper-V, they should probably go in
hyperv-tlfs.h.

> +
> /* 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;
> +}
> +

Like a comment in an earlier patch, I'm wondering if the bulk of
this code could move to ivm.c, to avoid overloading mshyperv.c.

> 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()) {

Also a bug fix to an earlier patch in this series.

> /*
> * 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;

This looks like a bug fix to Patch 8 of the series. It should be fixed
in patch 8.

> 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
>
> --
> 2.25.1

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