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Subject[tip: x86/seves] x86/sev-es: Handle NMI State
The following commit has been merged into the x86/seves branch of tip:

Commit-ID: 4ca68e023b11e4d5908bf9ee326fab01111d77d5
Gitweb: https://git.kernel.org/tip/4ca68e023b11e4d5908bf9ee326fab01111d77d5
Author: Joerg Roedel <jroedel@suse.de>
AuthorDate: Mon, 07 Sep 2020 15:16:11 +02:00
Committer: Borislav Petkov <bp@suse.de>
CommitterDate: Wed, 09 Sep 2020 18:02:35 +02:00

x86/sev-es: Handle NMI State

When running under SEV-ES, the kernel has to tell the hypervisor when to
open the NMI window again after an NMI was injected. This is done with
an NMI-complete message to the hypervisor.

Add code to the kernel's NMI handler to send this message right at the
beginning of do_nmi(). This always allows nesting NMIs.

[ bp: Mark __sev_es_nmi_complete() noinstr:
vmlinux.o: warning: objtool: exc_nmi()+0x17: call to __sev_es_nmi_complete()
leaves .noinstr.text section
While at it, use __pa_nodebug() for the same reason due to
CONFIG_DEBUG_VIRTUAL=y:
vmlinux.o: warning: objtool: __sev_es_nmi_complete()+0xd9: call to __phys_addr()
leaves .noinstr.text section ]

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200907131613.12703-71-joro@8bytes.org
---
arch/x86/include/asm/sev-es.h | 7 +++++++
arch/x86/include/uapi/asm/svm.h | 1 +
arch/x86/kernel/nmi.c | 6 ++++++
arch/x86/kernel/sev-es.c | 18 ++++++++++++++++++
4 files changed, 32 insertions(+)

diff --git a/arch/x86/include/asm/sev-es.h b/arch/x86/include/asm/sev-es.h
index db88e1c..e919f09 100644
--- a/arch/x86/include/asm/sev-es.h
+++ b/arch/x86/include/asm/sev-es.h
@@ -96,10 +96,17 @@ static __always_inline void sev_es_ist_exit(void)
__sev_es_ist_exit();
}
extern int sev_es_setup_ap_jump_table(struct real_mode_header *rmh);
+extern void __sev_es_nmi_complete(void);
+static __always_inline void sev_es_nmi_complete(void)
+{
+ if (static_branch_unlikely(&sev_es_enable_key))
+ __sev_es_nmi_complete();
+}
#else
static inline void sev_es_ist_enter(struct pt_regs *regs) { }
static inline void sev_es_ist_exit(void) { }
static inline int sev_es_setup_ap_jump_table(struct real_mode_header *rmh) { return 0; }
+static inline void sev_es_nmi_complete(void) { }
#endif

#endif
diff --git a/arch/x86/include/uapi/asm/svm.h b/arch/x86/include/uapi/asm/svm.h
index c1dcf3e..a7a3403 100644
--- a/arch/x86/include/uapi/asm/svm.h
+++ b/arch/x86/include/uapi/asm/svm.h
@@ -84,6 +84,7 @@
/* SEV-ES software-defined VMGEXIT events */
#define SVM_VMGEXIT_MMIO_READ 0x80000001
#define SVM_VMGEXIT_MMIO_WRITE 0x80000002
+#define SVM_VMGEXIT_NMI_COMPLETE 0x80000003
#define SVM_VMGEXIT_AP_HLT_LOOP 0x80000004
#define SVM_VMGEXIT_AP_JUMP_TABLE 0x80000005
#define SVM_VMGEXIT_SET_AP_JUMP_TABLE 0
diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c
index 4c89c4d..56b64d7 100644
--- a/arch/x86/kernel/nmi.c
+++ b/arch/x86/kernel/nmi.c
@@ -478,6 +478,12 @@ DEFINE_IDTENTRY_RAW(exc_nmi)
{
bool irq_state;

+ /*
+ * Re-enable NMIs right here when running as an SEV-ES guest. This might
+ * cause nested NMIs, but those can be handled safely.
+ */
+ sev_es_nmi_complete();
+
if (IS_ENABLED(CONFIG_SMP) && arch_cpu_is_offline(smp_processor_id()))
return;

diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c
index d1bcd0d..b6518e9 100644
--- a/arch/x86/kernel/sev-es.c
+++ b/arch/x86/kernel/sev-es.c
@@ -408,6 +408,24 @@ static bool vc_slow_virt_to_phys(struct ghcb *ghcb, struct es_em_ctxt *ctxt,
/* Include code shared with pre-decompression boot stage */
#include "sev-es-shared.c"

+void noinstr __sev_es_nmi_complete(void)
+{
+ struct ghcb_state state;
+ struct ghcb *ghcb;
+
+ ghcb = sev_es_get_ghcb(&state);
+
+ vc_ghcb_invalidate(ghcb);
+ ghcb_set_sw_exit_code(ghcb, SVM_VMGEXIT_NMI_COMPLETE);
+ ghcb_set_sw_exit_info_1(ghcb, 0);
+ ghcb_set_sw_exit_info_2(ghcb, 0);
+
+ sev_es_wr_ghcb_msr(__pa_nodebug(ghcb));
+ VMGEXIT();
+
+ sev_es_put_ghcb(&state);
+}
+
static u64 get_jump_table_addr(void)
{
struct ghcb_state state;
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