RE: [EXTERNAL] [RFC PATCH V6 13/14] x86/hyperv: Add smp support for sev-snp guest

[Saurabh Singh Sengar <ssengar@microsoft.com>]

> -----Original Message-----
> From: Tianyu Lan <ltykernel@gmail.com>
> Sent: Monday, May 15, 2023 10:29 PM
> To: luto@kernel.org; tglx@linutronix.de; mingo@redhat.com; bp@alien8.de;
> dave.hansen@linux.intel.com; x86@kernel.org; hpa@zytor.com;
> seanjc@google.com; pbonzini@redhat.com; jgross@suse.com; Tianyu Lan
> <Tianyu.Lan@microsoft.com>; kirill@shutemov.name;
> jiangshan.ljs@antgroup.com; peterz@infradead.org; ashish.kalra@amd.com;
> srutherford@google.com; akpm@linux-foundation.org;
> anshuman.khandual@arm.com; pawan.kumar.gupta@linux.intel.com;
> adrian.hunter@intel.com; daniel.sneddon@linux.intel.com;
> alexander.shishkin@linux.intel.com; sandipan.das@amd.com;
> ray.huang@amd.com; brijesh.singh@amd.com; michael.roth@amd.com;
> thomas.lendacky@amd.com; venu.busireddy@oracle.com;
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> fenghua.yu@intel.com
> Cc: pangupta@amd.com; linux-kernel@vger.kernel.org; kvm@vger.kernel.org;
> linux-hyperv@vger.kernel.org; linux-arch@vger.kernel.org
> Subject: [EXTERNAL] [RFC PATCH V6 13/14] x86/hyperv: Add smp support for
> sev-snp guest
> 
> From: Tianyu Lan <tiala@microsoft.com>
> 
> The wakeup_secondary_cpu callback was populated with wakeup_
> cpu_via_vmgexit() which doesn't work for Hyper-V and Hyper-V requires to
> call Hyper-V specific hvcall to start APs. So override it with Hyper-V specific
> hook to start AP sev_es_save_area data structure.
> 
> Signed-off-by: Tianyu Lan <tiala@microsoft.com>
> ---
> Change since RFC v5:
>        * Remove some redundant structure definitions
> 
> Change sicne RFC v3:
>        * Replace struct sev_es_save_area with struct
>          vmcb_save_area
>        * Move code from mshyperv.c to ivm.c
> 
> Change since RFC v2:
>        * Add helper function to initialize segment
>        * Fix some coding style
> ---
>  arch/x86/hyperv/ivm.c             | 98 +++++++++++++++++++++++++++++++
>  arch/x86/include/asm/mshyperv.h   | 10 ++++
>  arch/x86/kernel/cpu/mshyperv.c    | 13 +++-
>  include/asm-generic/hyperv-tlfs.h |  3 +-
>  4 files changed, 121 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/hyperv/ivm.c b/arch/x86/hyperv/ivm.c index
> 85e4378f052f..b7b8e1ba8223 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 {
> @@ -443,6 +447,100 @@ __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--);

can we restore local_irq here ?

> +
> +	if (!hv_result_success(ret)) {
> +		pr_err("HvCallStartVirtualProcessor failed: %llx\n", ret);
> +		goto done;

No need of goto here.

Regards,
Saurabh

> +	}
> +
> +done:
> +	local_irq_restore(flags);
> +	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 84e024ffacd5..9ad2a0f21d68
> 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); @@ -
> 263,6 +270,7 @@ 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_snp_boot_ap(int cpu, unsigned long start_ip);
> 
>  #ifdef CONFIG_AMD_MEM_ENCRYPT
>  void hv_ghcb_msr_write(u64 msr, u64 value); @@ -271,6 +279,7 @@ bool
> hv_ghcb_negotiate_protocol(void);  void 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 +287,7 @@ 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
> dea9b881180b..0c5f9f7bd7ba 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..92dcc530350c 100644
> --- a/include/asm-generic/hyperv-tlfs.h
> +++ b/include/asm-generic/hyperv-tlfs.h
> @@ -146,9 +146,9 @@ union hv_reference_tsc_msr {
>  /* Declare the various hypercall operations. */
>  #define HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE	0x0002
>  #define HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST	0x0003
> -#define HVCALL_ENABLE_VP_VTL			0x000f
>  #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
> @@ -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