[PATCH Part1 RFC v4 31/36] x86/sev: Provide support for SNP guest request NAEs

Brijesh Singh
2021-07-07T18:18:36Z

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 can be used by
driver or other subsystem to issue the request to PSP.

See SEV-SNP and GHCB spec for more details.

Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
arch/x86/include/uapi/asm/svm.h | 4 +++
arch/x86/kernel/sev.c | 57 +++++++++++++++++++++++++++++++++
include/linux/sev-guest.h | 48 +++++++++++++++++++++++++++
3 files changed, 109 insertions(+)
create mode 100644 include/linux/sev-guest.h

diff --git a/arch/x86/include/uapi/asm/svm.h b/arch/x86/include/uapi/asm/svm.h
index 997918f0a89a..9aaf0ab386ef 100644
--- a/arch/x86/include/uapi/asm/svm.h
+++ b/arch/x86/include/uapi/asm/svm.h
@@ -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
@@ -221,6 +223,8 @@
{ SVM_VMGEXIT_NMI_COMPLETE, "vmgexit_nmi_complete" }, \
{ SVM_VMGEXIT_AP_HLT_LOOP, "vmgexit_ap_hlt_loop" }, \
{ SVM_VMGEXIT_AP_JUMP_TABLE, "vmgexit_ap_jump_table" }, \
+ { SVM_VMGEXIT_GUEST_REQUEST, "vmgexit_guest_request" }, \
+ { SVM_VMGEXIT_EXT_GUEST_REQUEST, "vmgexit_ext_guest_request" }, \
{ SVM_VMGEXIT_PSC, "vmgexit_page_state_change" }, \
{ SVM_VMGEXIT_AP_CREATION, "vmgexit_ap_creation" }, \
{ SVM_VMGEXIT_HYPERVISOR_FEATURES, "vmgexit_hypervisor_feature" }, \
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 04ef5e79fa12..b85cab838372 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -21,6 +21,7 @@
#include <linux/cpumask.h>
#include <linux/log2.h>
#include <linux/efi.h>
+#include <linux/sev-guest.h>

#include <asm/cpu_entry_area.h>
#include <asm/stacktrace.h>
@@ -2024,3 +2025,59 @@ bool __init handle_vc_boot_ghcb(struct pt_regs *regs)
while (true)
halt();
}
+
+int snp_issue_guest_request(int type, struct snp_guest_request_data *input, unsigned long *fw_err)
+{
+ struct ghcb_state state;
+ unsigned long id, flags;
+ struct ghcb *ghcb;
+ int ret;
+
+ if (!sev_feature_enabled(SEV_SNP))
+ return -ENODEV;
+
+
+ local_irq_save(flags);
+
+ ghcb = __sev_get_ghcb(&state);
+ if (!ghcb)
+ return -ENODEV;
+
+ vc_ghcb_invalidate(ghcb);
+
+ if (type == GUEST_REQUEST) {
+ id = SVM_VMGEXIT_GUEST_REQUEST;
+ } else if (type == EXT_GUEST_REQUEST) {
+ id = SVM_VMGEXIT_EXT_GUEST_REQUEST;
+ ghcb_set_rax(ghcb, input->data_gpa);
+ ghcb_set_rbx(ghcb, input->data_npages);
+ } else {
+ ret = -EINVAL;
+ goto e_put;
+ }
+
+
+ ret = sev_es_ghcb_hv_call(ghcb, NULL, id, 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 (id == EXT_GUEST_REQUEST)
+ input->data_npages = ghcb_get_rbx(ghcb);
+
+ if (fw_err)
+ *fw_err = ghcb->save.sw_exit_info_2;
+
+ ret = -EIO;
+ goto e_put;
+ }
+
+e_put:
+ __sev_put_ghcb(&state);
+ local_irq_restore(flags);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(snp_issue_guest_request);
diff --git a/include/linux/sev-guest.h b/include/linux/sev-guest.h
new file mode 100644
index 000000000000..24dd17507789
--- /dev/null
+++ b/include/linux/sev-guest.h
@@ -0,0 +1,48 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * AMD Secure Encrypted Virtualization (SEV) guest driver interface
+ *
+ * Copyright (C) 2021 Advanced Micro Devices, Inc.
+ *
+ * Author: Brijesh Singh <brijesh.singh@amd.com>
+ *
+ */
+
+#ifndef __LINUX_SEV_GUEST_H_
+#define __LINUX_SEV_GUEST_H_
+
+#include <linux/types.h>
+
+enum vmgexit_type {
+ GUEST_REQUEST,
+ EXT_GUEST_REQUEST,
+
+ GUEST_REQUEST_MAX
+};
+
+/*
+ * The error code when the data_npages is too small. The error code
+ * is defined in the GHCB specification.
+ */
+#define SNP_GUEST_REQ_INVALID_LEN 0x100000000ULL
+
+struct snp_guest_request_data {
+ unsigned long req_gpa;
+ unsigned long resp_gpa;
+ unsigned long data_gpa;
+ unsigned int data_npages;
+};
+
+#ifdef CONFIG_AMD_MEM_ENCRYPT
+int snp_issue_guest_request(int vmgexit_type, struct snp_guest_request_data *input,
+ unsigned long *fw_err);
+#else
+
+static inline int snp_issue_guest_request(int type, struct snp_guest_request_data *input,
+ unsigned long *fw_err)
+{
+ return -ENODEV;
+}
+
+#endif /* CONFIG_AMD_MEM_ENCRYPT */
+#endif /* __LINUX_SEV_GUEST_H__ */
--
2.17.1