Received-SPF: softfail (google.com: domain of transitioning linux-kernel-owner@vger.kernel.org does not designate 23.128.96.19 as permitted sender) client-ip=23.128.96.19;
Received-SPF: Pass (protection.outlook.com: domain of amd.com designates
 165.204.84.17 as permitted sender) receiver=protection.outlook.com;
 client-ip=165.204.84.17; helo=SATLEXMB04.amd.com;
From:   Brijesh Singh <brijesh.singh@amd.com>
To:     <x86@kernel.org>, <linux-kernel@vger.kernel.org>,
        <kvm@vger.kernel.org>, <linux-efi@vger.kernel.org>,
        <platform-driver-x86@vger.kernel.org>,
        <linux-coco@lists.linux.dev>, <linux-mm@kvack.org>
CC:     Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Joerg Roedel <jroedel@suse.de>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Ard Biesheuvel <ardb@kernel.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Sean Christopherson <seanjc@google.com>,
        "Vitaly Kuznetsov" <vkuznets@redhat.com>,
        Jim Mattson <jmattson@google.com>,
        "Andy Lutomirski" <luto@kernel.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Sergio Lopez <slp@redhat.com>, Peter Gonda <pgonda@google.com>,
        "Peter Zijlstra" <peterz@infradead.org>,
        Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
        David Rientjes <rientjes@google.com>,
        Dov Murik <dovmurik@linux.ibm.com>,
        Tobin Feldman-Fitzthum <tobin@ibm.com>,
        Borislav Petkov <bp@alien8.de>,
        Michael Roth <michael.roth@amd.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        Andi Kleen <ak@linux.intel.com>,
        "Dr . David Alan Gilbert" <dgilbert@redhat.com>,
        <brijesh.ksingh@gmail.com>, <tony.luck@intel.com>,
        <marcorr@google.com>, <sathyanarayanan.kuppuswamy@linux.intel.com>,
        Brijesh Singh <brijesh.singh@amd.com>
Subject: [PATCH v12 17/46] x86/sev: Register GHCB memory when SEV-SNP is active
Date:   Mon, 7 Mar 2022 15:33:27 -0600
Message-ID: <20220307213356.2797205-18-brijesh.singh@amd.com>
In-Reply-To: <20220307213356.2797205-1-brijesh.singh@amd.com>
References: <20220307213356.2797205-1-brijesh.singh@amd.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Content-Type: text/plain
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 07 Mar 2022 21:34:56.7014
 (UTC)
X-MS-Exchange-CrossTenant-Network-Message-Id: 1b305bd5-18f5-4614-512f-08da0082532e
X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d
X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB04.amd.com]
X-MS-Exchange-CrossTenant-AuthSource: BN8NAM11FT048.eop-nam11.prod.protection.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Anonymous
X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem
X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW4PR12MB5668
X-Spam-Status: No, score=-2.0 required=5.0 tests=BAYES_00,DKIM_SIGNED,
	DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,
	MAILING_LIST_MULTI,RDNS_NONE,SPF_HELO_NONE,T_SCC_BODY_TEXT_LINE
	autolearn=no autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
	lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

The SEV-SNP guest is required by the GHCB spec to register the GHCB's
Guest Physical Address (GPA). This is because the hypervisor may prefer
that a guest use a consistent and/or specific GPA for the GHCB associated
with a vCPU. For more information, see the GHCB specification section
"GHCB GPA Registration".

Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 arch/x86/include/asm/sev.h   |  2 ++
 arch/x86/kernel/cpu/common.c |  4 +++
 arch/x86/kernel/head64.c     |  4 ++-
 arch/x86/kernel/sev-shared.c |  2 +-
 arch/x86/kernel/sev.c        | 47 +++++++++++++++++++++++++++---------
 5 files changed, 45 insertions(+), 14 deletions(-)

diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index e37451849165..48df02713ee0 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -122,6 +122,7 @@ static inline int pvalidate(unsigned long vaddr, bool rmp_psize, bool validate)
 
 	return rc;
 }
+void setup_ghcb(void);
 #else
 static inline void sev_es_ist_enter(struct pt_regs *regs) { }
 static inline void sev_es_ist_exit(void) { }
@@ -130,6 +131,7 @@ static inline void sev_es_nmi_complete(void) { }
 static inline int sev_es_efi_map_ghcbs(pgd_t *pgd) { return 0; }
 static inline int pvalidate(unsigned long vaddr, bool rmp_psize, bool validate) { return 0; }
 static inline int rmpadjust(unsigned long vaddr, bool rmp_psize, unsigned long attrs) { return 0; }
+static inline void setup_ghcb(void) { }
 #endif
 
 #endif
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 64deb7727d00..2e0dd7f4018e 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -59,6 +59,7 @@
 #include <asm/cpu_device_id.h>
 #include <asm/uv/uv.h>
 #include <asm/sigframe.h>
+#include <asm/sev.h>
 
 #include "cpu.h"
 
@@ -2067,6 +2068,9 @@ void cpu_init_exception_handling(void)
 
 	load_TR_desc();
 
+	/* GHCB need to be setup to handle #VC. */
+	setup_ghcb();
+
 	/* Finally load the IDT */
 	load_current_idt();
 }
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index cbc285ddc4ac..83514b9827e6 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -597,8 +597,10 @@ static void startup_64_load_idt(unsigned long physbase)
 void early_setup_idt(void)
 {
 	/* VMM Communication Exception */
-	if (IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT))
+	if (IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT)) {
+		setup_ghcb();
 		set_bringup_idt_handler(bringup_idt_table, X86_TRAP_VC, vc_boot_ghcb);
+	}
 
 	bringup_idt_descr.address = (unsigned long)bringup_idt_table;
 	native_load_idt(&bringup_idt_descr);
diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
index e9ff13cd90b0..3aaef1a18ffe 100644
--- a/arch/x86/kernel/sev-shared.c
+++ b/arch/x86/kernel/sev-shared.c
@@ -68,7 +68,7 @@ static u64 get_hv_features(void)
 	return GHCB_MSR_HV_FT_RESP_VAL(val);
 }
 
-static void __maybe_unused snp_register_ghcb_early(unsigned long paddr)
+static void snp_register_ghcb_early(unsigned long paddr)
 {
 	unsigned long pfn = paddr >> PAGE_SHIFT;
 	u64 val;
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index cb20fb0c608e..cc382c4f89ef 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -41,7 +41,7 @@ static struct ghcb boot_ghcb_page __bss_decrypted __aligned(PAGE_SIZE);
  * Needs to be in the .data section because we need it NULL before bss is
  * cleared
  */
-static struct ghcb __initdata *boot_ghcb;
+static struct ghcb *boot_ghcb __section(".data");
 
 /* Bitmap of SEV features supported by the hypervisor */
 static u64 sev_hv_features __ro_after_init;
@@ -647,15 +647,40 @@ static enum es_result vc_handle_msr(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
 	return ret;
 }
 
-/*
- * This function runs on the first #VC exception after the kernel
- * switched to virtual addresses.
- */
-static bool __init sev_es_setup_ghcb(void)
+static void snp_register_per_cpu_ghcb(void)
 {
+	struct sev_es_runtime_data *data;
+	struct ghcb *ghcb;
+
+	data = this_cpu_read(runtime_data);
+	ghcb = &data->ghcb_page;
+
+	snp_register_ghcb_early(__pa(ghcb));
+}
+
+void setup_ghcb(void)
+{
+	if (!cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT))
+		return;
+
 	/* First make sure the hypervisor talks a supported protocol. */
 	if (!sev_es_negotiate_protocol())
-		return false;
+		sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SEV_ES_GEN_REQ);
+
+	/*
+	 * Check whether the runtime #VC exception handler is active.
+	 * The runtime exception handler uses the per-CPU GHCB page, and
+	 * the GHCB page would be setup by sev_es_init_vc_handling().
+	 *
+	 * If SNP is active, then register the per-CPU GHCB page so that
+	 * the runtime exception handler can use it.
+	 */
+	if (initial_vc_handler == (unsigned long)kernel_exc_vmm_communication) {
+		if (cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
+			snp_register_per_cpu_ghcb();
+
+		return;
+	}
 
 	/*
 	 * Clear the boot_ghcb. The first exception comes in before the bss
@@ -666,7 +691,9 @@ static bool __init sev_es_setup_ghcb(void)
 	/* Alright - Make the boot-ghcb public */
 	boot_ghcb = &boot_ghcb_page;
 
-	return true;
+	/* SNP guest requires that GHCB GPA must be registered. */
+	if (cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
+		snp_register_ghcb_early(__pa(&boot_ghcb_page));
 }
 
 #ifdef CONFIG_HOTPLUG_CPU
@@ -1397,10 +1424,6 @@ bool __init handle_vc_boot_ghcb(struct pt_regs *regs)
 	struct es_em_ctxt ctxt;
 	enum es_result result;
 
-	/* Do initial setup or terminate the guest */
-	if (unlikely(boot_ghcb == NULL && !sev_es_setup_ghcb()))
-		sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SEV_ES_GEN_REQ);
-
 	vc_ghcb_invalidate(boot_ghcb);
 
 	result = vc_init_em_ctxt(&ctxt, regs, exit_code);
-- 
2.25.1