[RFC PATCH v2.1] x86/sev-es: Handle NMI State
From: Joerg Roedel <joro@8bytes.org>
Date: 2020-03-20 13:17:17
Also in:
kvm, lkml
Subsystem:
kernel virtual machine for x86 (kvm/x86), the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Sean Christopherson, Paolo Bonzini, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
On Thu, Mar 19, 2020 at 08:35:59AM -0700, Andy Lutomirski wrote:
1. Just put the NMI unmask in do_nmi(). The kernel *already* knows how to handle running do_nmi() with NMIs unmasked. This is much, much simpler than your code.
Okay, attached is the updated patch which implements this approach. I tested it in an SEV-ES guest with 'perf top' running for a little more than 30 minutes and all looked good. I also removed the dead code from the patch. From ec3b021c5d9130fd66e00d823c4fabc675c4b49e Mon Sep 17 00:00:00 2001 From: Joerg Roedel <redacted> Date: Tue, 28 Jan 2020 17:31:05 +0100 Subject: [PATCH] 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 kernels NMI handler to send this message right at the beginning of do_nmi(). This always allows nesting NMIs. Signed-off-by: Joerg Roedel <redacted> --- arch/x86/include/asm/sev-es.h | 2 ++ arch/x86/include/uapi/asm/svm.h | 1 + arch/x86/kernel/nmi.c | 8 ++++++++ arch/x86/kernel/sev-es.c | 18 ++++++++++++++++++ 4 files changed, 29 insertions(+)
diff --git a/arch/x86/include/asm/sev-es.h b/arch/x86/include/asm/sev-es.h
index 63acf50e6280..441ec1ba2cc7 100644
--- a/arch/x86/include/asm/sev-es.h
+++ b/arch/x86/include/asm/sev-es.h@@ -82,11 +82,13 @@ struct real_mode_header; #ifdef CONFIG_AMD_MEM_ENCRYPT int sev_es_setup_ap_jump_table(struct real_mode_header *rmh); +void sev_es_nmi_complete(void); #else /* CONFIG_AMD_MEM_ENCRYPT */ 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 /* CONFIG_AMD_MEM_ENCRYPT*/ #endif
diff --git a/arch/x86/include/uapi/asm/svm.h b/arch/x86/include/uapi/asm/svm.h
index 20a05839dd9a..0f837339db66 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 54c21d6abd5a..fc872a7e0ed1 100644
--- a/arch/x86/kernel/nmi.c
+++ b/arch/x86/kernel/nmi.c@@ -37,6 +37,7 @@ #include <asm/reboot.h> #include <asm/cache.h> #include <asm/nospec-branch.h> +#include <asm/sev-es.h> #define CREATE_TRACE_POINTS #include <trace/events/nmi.h>
@@ -510,6 +511,13 @@ NOKPROBE_SYMBOL(is_debug_stack); dotraplinkage notrace void do_nmi(struct pt_regs *regs, long error_code) { + /* + * Re-enable NMIs right here when running as an SEV-ES guest. This might + * cause nested NMIs, but those can be handled safely. + */ + if (sev_es_active()) + sev_es_nmi_complete(); + if (IS_ENABLED(CONFIG_SMP) && cpu_is_offline(smp_processor_id())) return;
diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c
index 3c22f256645e..a7e2739771e7 100644
--- a/arch/x86/kernel/sev-es.c
+++ b/arch/x86/kernel/sev-es.c@@ -270,6 +270,24 @@ static phys_addr_t vc_slow_virt_to_phys(struct ghcb *ghcb, long vaddr) /* Include code shared with pre-decompression boot stage */ #include "sev-es-shared.c" +void 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(ghcb)); + VMGEXIT(); + + sev_es_put_ghcb(&state); +} + static u64 sev_es_get_jump_table_addr(void) { struct ghcb_state state;
--
2.16.4