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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
This commit is contained in:
Joerg Roedel 2020-09-07 15:16:11 +02:00 committed by Borislav Petkov
parent 094794f597
commit 4ca68e023b
4 changed files with 32 additions and 0 deletions
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7
arch/x86/include/asm/sev-es.h
View File

@ -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

1
arch/x86/include/uapi/asm/svm.h
View File

@ -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

6
arch/x86/kernel/nmi.c
View File

@ -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;

18
arch/x86/kernel/sev-es.c
View File

@ -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;