linux-kernel - [PATCH 68/70] x86/sev-es: Support CPU offline/online

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Message-Id: <20200319091407.1481-69-joro@8bytes.org>
Date:   Thu, 19 Mar 2020 10:14:05 +0100
From:   Joerg Roedel <joro@...tes.org>
To:     x86@...nel.org
Cc:     hpa@...or.com, Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Hellstrom <thellstrom@...are.com>,
        Jiri Slaby <jslaby@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Juergen Gross <jgross@...e.com>,
        Kees Cook <keescook@...omium.org>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        Joerg Roedel <joro@...tes.org>, Joerg Roedel <jroedel@...e.de>
Subject: [PATCH 68/70] x86/sev-es: Support CPU offline/online

From: Joerg Roedel <jroedel@...e.de>

Add a play_dead handler when running under SEV-ES. This is needed
because the hypervisor can't deliver an SIPI request to restart the AP.
Instead the kernel has to issue a VMGEXIT to halt the VCPU. When the
hypervisor would deliver and SIPI is wakes up the VCPU instead.

Signed-off-by: Joerg Roedel <jroedel@...e.de>
---
 arch/x86/include/uapi/asm/svm.h |  1 +
 arch/x86/kernel/sev-es.c        | 58 +++++++++++++++++++++++++++++++++
 2 files changed, 59 insertions(+)

diff --git a/arch/x86/include/uapi/asm/svm.h b/arch/x86/include/uapi/asm/svm.h
index a19ce9681ec2..20a05839dd9a 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_AP_HLT_LOOP			0x80000004
 #define SVM_VMGEXIT_AP_JUMP_TABLE		0x80000005
 #define		SVM_VMGEXIT_SET_AP_JUMP_TABLE			0
 #define		SVM_VMGEXIT_GET_AP_JUMP_TABLE			1
diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c
index f56bdaf12fbe..3c22f256645e 100644
--- a/arch/x86/kernel/sev-es.c
+++ b/arch/x86/kernel/sev-es.c
@@ -23,6 +23,8 @@
 #include <asm/processor.h>
 #include <asm/traps.h>
 #include <asm/svm.h>
+#include <asm/smp.h>
+#include <asm/cpu.h>
 
 #define DR7_RESET_VALUE        0x400
 
@@ -381,6 +383,60 @@ static bool __init sev_es_setup_ghcb(void)
 	return true;
 }
 
+#ifdef CONFIG_HOTPLUG_CPU
+static void sev_es_ap_hlt_loop(void)
+{
+	struct ghcb_state state;
+	struct ghcb *ghcb;
+
+	ghcb = sev_es_get_ghcb(&state);
+
+	while (true) {
+		vc_ghcb_invalidate(ghcb);
+		ghcb_set_sw_exit_code(ghcb, SVM_VMGEXIT_AP_HLT_LOOP);
+		ghcb_set_sw_exit_info_1(ghcb, 0);
+		ghcb_set_sw_exit_info_2(ghcb, 0);
+
+		sev_es_wr_ghcb_msr(__pa(ghcb));
+		VMGEXIT();
+
+		/* Wakup Signal? */
+		if (ghcb_is_valid_sw_exit_info_2(ghcb) &&
+		    ghcb->save.sw_exit_info_2 != 0)
+			break;
+	}
+
+	sev_es_put_ghcb(&state);
+}
+
+void sev_es_play_dead(void)
+{
+	play_dead_common();
+
+	/* IRQs now disabled */
+
+	sev_es_ap_hlt_loop();
+
+	/*
+	 * If we get here, the VCPU was woken up again. Jump to CPU
+	 * startup code to get it back online.
+	 */
+
+	start_cpu();
+}
+#else  /* CONFIG_HOTPLUG_CPU */
+#define sev_es_play_dead	native_play_dead
+#endif /* CONFIG_HOTPLUG_CPU */
+
+#ifdef CONFIG_SMP
+static void sev_es_setup_play_dead(void)
+{
+	smp_ops.play_dead = sev_es_play_dead;
+}
+#else
+static inline void sev_es_setup_play_dead(void) { }
+#endif
+
 void sev_es_init_ghcbs(void)
 {
 	int cpu;
@@ -399,6 +455,8 @@ void sev_es_init_ghcbs(void)
 				     sizeof(*ghcb) >> PAGE_SHIFT);
 		memset(ghcb, 0, sizeof(*ghcb));
 	}
+
+	sev_es_setup_play_dead();
 }
 
 static void __init vc_early_vc_forward_exception(struct es_em_ctxt *ctxt)
-- 
2.17.1