linux-kernel - [PATCH v6 44/76] x86/sev-es: Setup per-cpu GHCBs for the runtime handler

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Date:   Mon, 24 Aug 2020 10:54:39 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     x86@...nel.org
Cc:     Joerg Roedel <joro@...tes.org>, Joerg Roedel <jroedel@...e.de>,
        Tom Lendacky <thomas.lendacky@....com>, hpa@...or.com,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Jiri Slaby <jslaby@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Juergen Gross <jgross@...e.com>,
        Kees Cook <keescook@...omium.org>,
        David Rientjes <rientjes@...gle.com>,
        Cfir Cohen <cfir@...gle.com>,
        Erdem Aktas <erdemaktas@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mike Stunes <mstunes@...are.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Martin Radev <martin.b.radev@...il.com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org
Subject: [PATCH v6 44/76] x86/sev-es: Setup per-cpu GHCBs for the runtime handler

From: Tom Lendacky <thomas.lendacky@....com>

The runtime handler needs a GHCB per CPU. Set them up and map them
unencrypted.

Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
Signed-off-by: Joerg Roedel <jroedel@...e.de>
Link: https://lore.kernel.org/r/20200724160336.5435-44-joro@8bytes.org
---
 arch/x86/include/asm/mem_encrypt.h |  2 ++
 arch/x86/kernel/sev-es.c           | 56 +++++++++++++++++++++++++++++-
 arch/x86/kernel/traps.c            |  3 ++
 3 files changed, 60 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/mem_encrypt.h b/arch/x86/include/asm/mem_encrypt.h
index 4e72b73a9cb5..c9f5df0a1c10 100644
--- a/arch/x86/include/asm/mem_encrypt.h
+++ b/arch/x86/include/asm/mem_encrypt.h
@@ -49,6 +49,7 @@ void __init mem_encrypt_free_decrypted_mem(void);
 /* Architecture __weak replacement functions */
 void __init mem_encrypt_init(void);
 
+void __init sev_es_init_vc_handling(void);
 bool sme_active(void);
 bool sev_active(void);
 bool sev_es_active(void);
@@ -72,6 +73,7 @@ static inline void __init sme_early_init(void) { }
 static inline void __init sme_encrypt_kernel(struct boot_params *bp) { }
 static inline void __init sme_enable(struct boot_params *bp) { }
 
+static inline void sev_es_init_vc_handling(void) { }
 static inline bool sme_active(void) { return false; }
 static inline bool sev_active(void) { return false; }
 static inline bool sev_es_active(void) { return false; }
diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c
index bb3e702a71eb..734afaee378d 100644
--- a/arch/x86/kernel/sev-es.c
+++ b/arch/x86/kernel/sev-es.c
@@ -8,8 +8,13 @@
  */
 
 #include <linux/sched/debug.h>	/* For show_regs() */
-#include <linux/kernel.h>
+#include <linux/percpu-defs.h>
+#include <linux/mem_encrypt.h>
 #include <linux/printk.h>
+#include <linux/mm_types.h>
+#include <linux/set_memory.h>
+#include <linux/memblock.h>
+#include <linux/kernel.h>
 #include <linux/mm.h>
 
 #include <asm/sev-es.h>
@@ -29,6 +34,13 @@ static struct ghcb boot_ghcb_page __bss_decrypted __aligned(PAGE_SIZE);
  */
 static struct ghcb __initdata *boot_ghcb;
 
+/* #VC handler runtime per-cpu data */
+struct sev_es_runtime_data {
+	struct ghcb ghcb_page;
+};
+
+static DEFINE_PER_CPU(struct sev_es_runtime_data*, runtime_data);
+
 /* Needed in vc_early_forward_exception */
 void do_early_exception(struct pt_regs *regs, int trapnr);
 
@@ -198,6 +210,48 @@ static bool __init sev_es_setup_ghcb(void)
 	return true;
 }
 
+static void __init sev_es_alloc_runtime_data(int cpu)
+{
+	struct sev_es_runtime_data *data;
+
+	data = memblock_alloc(sizeof(*data), PAGE_SIZE);
+	if (!data)
+		panic("Can't allocate SEV-ES runtime data");
+
+	per_cpu(runtime_data, cpu) = data;
+}
+
+static void __init sev_es_init_ghcb(int cpu)
+{
+	struct sev_es_runtime_data *data;
+	int err;
+
+	data = per_cpu(runtime_data, cpu);
+
+	err = early_set_memory_decrypted((unsigned long)&data->ghcb_page,
+					 sizeof(data->ghcb_page));
+	if (err)
+		panic("Can not map GHCBs unencrypted");
+
+	memset(&data->ghcb_page, 0, sizeof(data->ghcb_page));
+}
+
+void __init sev_es_init_vc_handling(void)
+{
+	int cpu;
+
+	BUILD_BUG_ON((offsetof(struct sev_es_runtime_data, ghcb_page) % PAGE_SIZE) != 0);
+
+	if (!sev_es_active())
+		return;
+
+	/* Initialize per-cpu GHCB pages */
+	for_each_possible_cpu(cpu) {
+		sev_es_alloc_runtime_data(cpu);
+		sev_es_init_ghcb(cpu);
+	}
+}
+
 static void __init vc_early_forward_exception(struct es_em_ctxt *ctxt)
 {
 	int trapnr = ctxt->fi.vector;
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 1f66d2d1e998..74cfe6eb7ebb 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -1077,6 +1077,9 @@ void __init trap_init(void)
 	/* Init cpu_entry_area before IST entries are set up */
 	setup_cpu_entry_areas();
 
+	/* Init GHCB memory pages when running as an SEV-ES guest */
+	sev_es_init_vc_handling();
+
 	idt_setup_traps();
 
 	/*
-- 
2.28.0