Commit d5af44dd authored by Brijesh Singh's avatar Brijesh Singh Committed by Borislav Petkov
Browse files

x86/sev: Provide support for SNP guest request NAEs 



Version 2 of GHCB specification provides SNP_GUEST_REQUEST and
SNP_EXT_GUEST_REQUEST NAE that can be used by the SNP guest to
communicate with the PSP.

While at it, add a snp_issue_guest_request() helper that will be used by
driver or other subsystem to issue the request to PSP.

See SEV-SNP firmware and GHCB spec for more details.

Signed-off-by: default avatarBrijesh Singh <brijesh.singh@amd.com>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-42-brijesh.singh@amd.com
parent ba37a143

arch/x86/include/asm/sev-common.h

+3 −0
Original line number Diff line number Diff line
@@ -128,6 +128,9 @@ struct snp_psc_desc { 
	struct psc_entry entries[VMGEXIT_PSC_MAX_ENTRY];

} __packed;



/* Guest message request error code */

#define SNP_GUEST_REQ_INVALID_LEN	BIT_ULL(32)



#define GHCB_MSR_TERM_REQ		0x100

#define GHCB_MSR_TERM_REASON_SET_POS	12

#define GHCB_MSR_TERM_REASON_SET_MASK	0xf

arch/x86/include/asm/sev.h

+14 −0
Original line number Diff line number Diff line
@@ -87,6 +87,14 @@ extern bool handle_vc_boot_ghcb(struct pt_regs *regs); 


#define RMPADJUST_VMSA_PAGE_BIT		BIT(16)



/* SNP Guest message request */

struct snp_req_data {

	unsigned long req_gpa;

	unsigned long resp_gpa;

	unsigned long data_gpa;

	unsigned int data_npages;

};



#ifdef CONFIG_AMD_MEM_ENCRYPT

extern struct static_key_false sev_es_enable_key;

extern void __sev_es_ist_enter(struct pt_regs *regs);
@@ -154,6 +162,7 @@ void snp_set_memory_private(unsigned long vaddr, unsigned int npages); 
void snp_set_wakeup_secondary_cpu(void);

bool snp_init(struct boot_params *bp);

void snp_abort(void);

int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, unsigned long *fw_err);

#else

static inline void sev_es_ist_enter(struct pt_regs *regs) { }

static inline void sev_es_ist_exit(void) { }
@@ -173,6 +182,11 @@ static inline void snp_set_memory_private(unsigned long vaddr, unsigned int npag 
static inline void snp_set_wakeup_secondary_cpu(void) { }

static inline bool snp_init(struct boot_params *bp) { return false; }

static inline void snp_abort(void) { }

static inline int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input,

					  unsigned long *fw_err)

{

	return -ENOTTY;

}

#endif



#endif

arch/x86/include/uapi/asm/svm.h

+4 −0
Original line number Diff line number Diff line
@@ -109,6 +109,8 @@ 
#define SVM_VMGEXIT_SET_AP_JUMP_TABLE		0

#define SVM_VMGEXIT_GET_AP_JUMP_TABLE		1

#define SVM_VMGEXIT_PSC				0x80000010

#define SVM_VMGEXIT_GUEST_REQUEST		0x80000011

#define SVM_VMGEXIT_EXT_GUEST_REQUEST		0x80000012

#define SVM_VMGEXIT_AP_CREATION			0x80000013

#define SVM_VMGEXIT_AP_CREATE_ON_INIT		0

#define SVM_VMGEXIT_AP_CREATE			1
@@ -225,6 +227,8 @@ 
	{ SVM_VMGEXIT_AP_HLT_LOOP,	"vmgexit_ap_hlt_loop" }, \

	{ SVM_VMGEXIT_AP_JUMP_TABLE,	"vmgexit_ap_jump_table" }, \

	{ SVM_VMGEXIT_PSC,		"vmgexit_page_state_change" }, \

	{ SVM_VMGEXIT_GUEST_REQUEST,	"vmgexit_guest_request" }, \

	{ SVM_VMGEXIT_EXT_GUEST_REQUEST, "vmgexit_ext_guest_request" }, \

	{ SVM_VMGEXIT_AP_CREATION,	"vmgexit_ap_creation" }, \

	{ SVM_VMGEXIT_HV_FEATURES,	"vmgexit_hypervisor_feature" }, \

	{ SVM_EXIT_ERR,         "invalid_guest_state" }

arch/x86/kernel/sev.c

+57 −0
Original line number Diff line number Diff line
@@ -2106,3 +2106,60 @@ static int __init init_sev_config(char *str) 
	return 1;

}

__setup("sev=", init_sev_config);



int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, unsigned long *fw_err)

{

	struct ghcb_state state;

	struct es_em_ctxt ctxt;

	unsigned long flags;

	struct ghcb *ghcb;

	int ret;



	if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP))

		return -ENODEV;



	if (!fw_err)

		return -EINVAL;



	/*

	 * __sev_get_ghcb() needs to run with IRQs disabled because it is using

	 * a per-CPU GHCB.

	 */

	local_irq_save(flags);



	ghcb = __sev_get_ghcb(&state);

	if (!ghcb) {

		ret = -EIO;

		goto e_restore_irq;

	}



	vc_ghcb_invalidate(ghcb);



	if (exit_code == SVM_VMGEXIT_EXT_GUEST_REQUEST) {

		ghcb_set_rax(ghcb, input->data_gpa);

		ghcb_set_rbx(ghcb, input->data_npages);

	}



	ret = sev_es_ghcb_hv_call(ghcb, true, &ctxt, exit_code, input->req_gpa, input->resp_gpa);

	if (ret)

		goto e_put;



	if (ghcb->save.sw_exit_info_2) {

		/* Number of expected pages are returned in RBX */

		if (exit_code == SVM_VMGEXIT_EXT_GUEST_REQUEST &&

		    ghcb->save.sw_exit_info_2 == SNP_GUEST_REQ_INVALID_LEN)

			input->data_npages = ghcb_get_rbx(ghcb);



		*fw_err = ghcb->save.sw_exit_info_2;



		ret = -EIO;

	}



e_put:

	__sev_put_ghcb(&state);

e_restore_irq:

	local_irq_restore(flags);



	return ret;

}

EXPORT_SYMBOL_GPL(snp_issue_guest_request);