RE: [PATCH V2 8/9] x86/hyperv: Add smp support for SEV-SNP guest

From: Michael Kelley (LINUX)
Date: Tue Jul 04 2023 - 10:24:39 EST

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From: Tianyu Lan <ltykernel@xxxxxxxxx> Sent: Monday, June 26, 2023 8:23 PM
>
> In the AMD SEV-SNP guest, AP needs to be started up via sev es
> save area and Hyper-V requires to call HVCALL_START_VP hypercall
> to pass the gpa of sev es save area with AP's vp index and VTL(Virtual
> trust level) parameters. Override wakeup_secondary_cpu_64 callback
> with hv_snp_boot_ap.
>
> Signed-off-by: Tianyu Lan <tiala@xxxxxxxxxxxxx>
> ---
> arch/x86/hyperv/ivm.c | 95 +++++++++++++++++++++++++++++++
> arch/x86/include/asm/mshyperv.h | 9 +++
> arch/x86/kernel/cpu/mshyperv.c | 13 ++++-
> include/asm-generic/hyperv-tlfs.h | 1 +
> 4 files changed, 116 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/hyperv/ivm.c b/arch/x86/hyperv/ivm.c
> index b1639ec07155..9b307f99b540 100644
> --- a/arch/x86/hyperv/ivm.c
> +++ b/arch/x86/hyperv/ivm.c
> @@ -22,11 +22,15 @@
> #include <asm/sev.h>
> #include <asm/realmode.h>
> #include <asm/e820/api.h>
> +#include <asm/desc.h>
>
> #ifdef CONFIG_AMD_MEM_ENCRYPT
>
> #define GHCB_USAGE_HYPERV_CALL 1
>
> +static u8 ap_start_input_arg[PAGE_SIZE] __bss_decrypted __aligned(PAGE_SIZE);
> +static u8 ap_start_stack[PAGE_SIZE] __aligned(PAGE_SIZE);
> +
> union hv_ghcb {
> struct ghcb ghcb;
> struct {
> @@ -449,6 +453,97 @@ __init void hv_sev_init_mem_and_cpu(void)
> }
> }
>
> +#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 sev_es_save_area *vmsa = (struct sev_es_save_area *)
> + __get_free_page(GFP_KERNEL | __GFP_ZERO);
> + struct desc_ptr gdtr;
> + u64 ret, rmp_adjust, retry = 5;
> + struct hv_enable_vp_vtl *start_vp_input;
> + 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];
> +
> + /*
> + * Set the SNP-specific fields for this VMSA:
> + * VMPL level
> + * SEV_FEATURES (matches the SEV STATUS MSR right shifted 2 bits)
> + */
> + vmsa->vmpl = 0;
> + vmsa->sev_features = sev_status >> 2;
> +
> + /*
> + * Running at VMPL0 allows the kernel to change the VMSA bit for a page
> + * using the RMPADJUST instruction. However, for the instruction to
> + * succeed it must target the permissions of a lesser privileged
> + * (higher numbered) VMPL level, so use VMPL1 (refer to the RMPADJUST
> + * instruction in the AMD64 APM Volume 3).
> + */
> + rmp_adjust = RMPADJUST_VMSA_PAGE_BIT | 1;
> + ret = rmpadjust((unsigned long)vmsa, RMP_PG_SIZE_4K,
> + rmp_adjust);
> + if (ret != 0) {
> + pr_err("RMPADJUST(%llx) failed: %llx\n", (u64)vmsa, ret);
> + return ret;
> + }
> +
> + local_irq_save(flags);
> + start_vp_input =
> + (struct hv_enable_vp_vtl *)ap_start_input_arg;
> + memset(start_vp_input, 0, sizeof(*start_vp_input));
> + start_vp_input->partition_id = -1;
> + start_vp_input->vp_index = cpu;
> + start_vp_input->target_vtl.target_vtl = ms_hyperv.vtl;
> + *(u64 *)&start_vp_input->vp_context = __pa(vmsa) | 1;
> +
> + do {
> + ret = hv_do_hypercall(HVCALL_START_VP,
> + start_vp_input, NULL);
> + } while (hv_result(ret) == HV_STATUS_TIME_OUT && retry--);
> +
> + local_irq_restore(flags);
> +
> + if (!hv_result_success(ret))
> + pr_err("HvCallStartVirtualProcessor failed: %llx\n", ret);
> + return ret;
> +}
> +
> void __init hv_vtom_init(void)
> {
> /*
> diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
> index 7a9a6cdc2ae9..804c67475054 100644
> --- a/arch/x86/include/asm/mshyperv.h
> +++ b/arch/x86/include/asm/mshyperv.h
> @@ -65,6 +65,13 @@ struct memory_map_entry {
> u32 reserved;
> };
>
> +/*
> + * 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
> +
> 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);
> @@ -271,6 +278,7 @@ bool hv_ghcb_negotiate_protocol(void);
> void __noreturn hv_ghcb_terminate(unsigned int set, unsigned int reason);
> void hv_vtom_init(void);
> void hv_sev_init_mem_and_cpu(void);
> +int hv_snp_boot_ap(int cpu, unsigned long start_ip);
> #else
> static inline void hv_ghcb_msr_write(u64 msr, u64 value) {}
> static inline void hv_ghcb_msr_read(u64 msr, u64 *value) {}
> @@ -278,6 +286,7 @@ static inline bool hv_ghcb_negotiate_protocol(void) { return false; }
> static inline void hv_ghcb_terminate(unsigned int set, unsigned int reason) {}
> static inline void hv_vtom_init(void) {}
> static inline void hv_sev_init_mem_and_cpu(void) {}
> +static int hv_snp_boot_ap(int cpu, unsigned long start_ip) {}
> #endif
>
> extern bool hv_isolation_type_snp(void);
> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> index d3bb921ee7fe..8e1d9ed6a1e0 100644
> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -295,6 +295,16 @@ static void __init hv_smp_prepare_cpus(unsigned int
> max_cpus)
>
> native_smp_prepare_cpus(max_cpus);
>
> + /*
> + * Override wakeup_secondary_cpu_64 callback for SEV-SNP
> + * enlightened guest.
> + */
> + if (hv_isolation_type_en_snp())
> + apic->wakeup_secondary_cpu_64 = hv_snp_boot_ap;
> +
> + if (!hv_root_partition)
> + return;
> +
> #ifdef CONFIG_X86_64
> for_each_present_cpu(i) {
> if (i == 0)
> @@ -502,8 +512,7 @@ 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
>
> /*
> diff --git a/include/asm-generic/hyperv-tlfs.h b/include/asm-generic/hyperv-tlfs.h
> index f4e4cc4f965f..fdac4a1714ec 100644
> --- a/include/asm-generic/hyperv-tlfs.h
> +++ b/include/asm-generic/hyperv-tlfs.h
> @@ -223,6 +223,7 @@ 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 120
> #define HV_STATUS_VTL_ALREADY_ENABLED 134
>
> /*
> --
> 2.25.1

Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>

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