x86/sev: Register GHCB memory when SEV-SNP is active

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 uses a consistent and/or specific GPA for the GHCB associated
with a vCPU. For more information, see the GHCB specification section
"GHCB GPA Registration".

  [ bp: Cleanup comments. ]

Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-18-brijesh.singh@amd.com

diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index e374518491654d67a5016fd51def578f8d3ca578..48df02713ee001046a95dae2e6c2cee374422989 100644 (file)
--- 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 ed4417500700416768b6096a905e3e5d090b4d98..9e45521338721f05cc3c8b92997e5ed64a966daf 100644 (file)
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -60,6 +60,7 @@
 #include <asm/uv/uv.h>
 #include <asm/sigframe.h>
 #include <asm/traps.h>
+#include <asm/sev.h>
 
 #include "cpu.h"
 
@@ -2124,6 +2125,9 @@ void cpu_init_exception_handling(void)
 
        load_TR_desc();
 
+       /* GHCB needs 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 cbc285ddc4acafb787a53f4dd471ddae72cc4908..83514b9827e6c01d47a652d2d5177175f0cbb4c6 100644 (file)
--- 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 e9ff13cd90b0757c6be568ff97954ddb55c77570..3aaef1a18ffed03080dcaff89eba30bb14d622e3 100644 (file)
--- 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 cb20fb0c608e31234b122e63610c70b052951585..39c87469ee0b0b6e777c014e5e8b8fc6cddc209b 100644 (file)
--- 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 +647,39 @@ 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. It uses
+        * the per-CPU GHCB page which is set up by sev_es_init_vc_handling().
+        *
+        * If SNP is active, 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 +690,9 @@ 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 +1423,6 @@ 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);