x86/kvm: Add guest support for detecting and enabling SEV Live Migration feature.

The guest support for detecting and enabling SEV Live migration
feature uses the following logic :

 - kvm_init_plaform() checks if its booted under the EFI

   - If not EFI,

     i) if kvm_para_has_feature(KVM_FEATURE_MIGRATION_CONTROL), issue a wrmsrl()
         to enable the SEV live migration support

   - If EFI,

     i) If kvm_para_has_feature(KVM_FEATURE_MIGRATION_CONTROL), read
        the UEFI variable which indicates OVMF support for live migration

     ii) the variable indicates live migration is supported, issue a wrmsrl() to
          enable the SEV live migration support

The EFI live migration check is done using a late_initcall() callback.

Also, ensure that _bss_decrypted section is marked as decrypted in the
hypervisor's guest page encryption status tracking.

Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
Reviewed-by: Steve Rutherford <srutherford@google.com>
Message-Id: <b4453e4c87103ebef12217d2505ea99a1c3e0f0f.1629726117.git.ashish.kalra@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/include/asm/mem_encrypt.h b/arch/x86/include/asm/mem_encrypt.h
index 9c80c68..8dd373c 100644 (file)
--- a/arch/x86/include/asm/mem_encrypt.h
+++ b/arch/x86/include/asm/mem_encrypt.h
@@ -43,6 +43,8 @@ void __init sme_enable(struct boot_params *bp);
 
 int __init early_set_memory_decrypted(unsigned long vaddr, unsigned long size);
 int __init early_set_memory_encrypted(unsigned long vaddr, unsigned long size);
+void __init early_set_mem_enc_dec_hypercall(unsigned long vaddr, int npages,
+                                           bool enc);
 
 void __init mem_encrypt_free_decrypted_mem(void);
 
@@ -83,6 +85,8 @@ static inline int __init
 early_set_memory_decrypted(unsigned long vaddr, unsigned long size) { return 0; }
 static inline int __init
 early_set_memory_encrypted(unsigned long vaddr, unsigned long size) { return 0; }
+static inline void __init
+early_set_mem_enc_dec_hypercall(unsigned long vaddr, int npages, bool enc) {}
 
 static inline void mem_encrypt_free_decrypted_mem(void) { }
 

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index b656456..a672a2e 100644 (file)
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -27,6 +27,7 @@
 #include <linux/nmi.h>
 #include <linux/swait.h>
 #include <linux/syscore_ops.h>
+#include <linux/efi.h>
 #include <asm/timer.h>
 #include <asm/cpu.h>
 #include <asm/traps.h>
@@ -40,6 +41,7 @@
 #include <asm/ptrace.h>
 #include <asm/reboot.h>
 #include <asm/svm.h>
+#include <asm/e820/api.h>
 
 DEFINE_STATIC_KEY_FALSE(kvm_async_pf_enabled);
 
@@ -433,6 +435,8 @@ static void kvm_guest_cpu_offline(bool shutdown)
        kvm_disable_steal_time();
        if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
                wrmsrl(MSR_KVM_PV_EOI_EN, 0);
+       if (kvm_para_has_feature(KVM_FEATURE_MIGRATION_CONTROL))
+               wrmsrl(MSR_KVM_MIGRATION_CONTROL, 0);
        kvm_pv_disable_apf();
        if (!shutdown)
                apf_task_wake_all();
@@ -547,6 +551,55 @@ static void kvm_send_ipi_mask_allbutself(const struct cpumask *mask, int vector)
        __send_ipi_mask(local_mask, vector);
 }
 
+static int __init setup_efi_kvm_sev_migration(void)
+{
+       efi_char16_t efi_sev_live_migration_enabled[] = L"SevLiveMigrationEnabled";
+       efi_guid_t efi_variable_guid = AMD_SEV_MEM_ENCRYPT_GUID;
+       efi_status_t status;
+       unsigned long size;
+       bool enabled;
+
+       if (!sev_active() ||
+           !kvm_para_has_feature(KVM_FEATURE_MIGRATION_CONTROL))
+               return 0;
+
+       if (!efi_enabled(EFI_BOOT))
+               return 0;
+
+       if (!efi_enabled(EFI_RUNTIME_SERVICES)) {
+               pr_info("%s : EFI runtime services are not enabled\n", __func__);
+               return 0;
+       }
+
+       size = sizeof(enabled);
+
+       /* Get variable contents into buffer */
+       status = efi.get_variable(efi_sev_live_migration_enabled,
+                                 &efi_variable_guid, NULL, &size, &enabled);
+
+       if (status == EFI_NOT_FOUND) {
+               pr_info("%s : EFI live migration variable not found\n", __func__);
+               return 0;
+       }
+
+       if (status != EFI_SUCCESS) {
+               pr_info("%s : EFI variable retrieval failed\n", __func__);
+               return 0;
+       }
+
+       if (enabled == 0) {
+               pr_info("%s: live migration disabled in EFI\n", __func__);
+               return 0;
+       }
+
+       pr_info("%s : live migration enabled in EFI\n", __func__);
+       wrmsrl(MSR_KVM_MIGRATION_CONTROL, KVM_MIGRATION_READY);
+
+       return 1;
+}
+
+late_initcall(setup_efi_kvm_sev_migration);
+
 /*
  * Set the IPI entry points
  */
@@ -805,8 +858,37 @@ static bool __init kvm_msi_ext_dest_id(void)
        return kvm_para_has_feature(KVM_FEATURE_MSI_EXT_DEST_ID);
 }
 
+static void kvm_sev_hc_page_enc_status(unsigned long pfn, int npages, bool enc)
+{
+       kvm_sev_hypercall3(KVM_HC_MAP_GPA_RANGE, pfn << PAGE_SHIFT, npages,
+                          KVM_MAP_GPA_RANGE_ENC_STAT(enc) | KVM_MAP_GPA_RANGE_PAGE_SZ_4K);
+}
+
 static void __init kvm_init_platform(void)
 {
+       if (sev_active() &&
+           kvm_para_has_feature(KVM_FEATURE_MIGRATION_CONTROL)) {
+               unsigned long nr_pages;
+
+               pv_ops.mmu.notify_page_enc_status_changed =
+                       kvm_sev_hc_page_enc_status;
+
+               /*
+                * Ensure that _bss_decrypted section is marked as decrypted in the
+                * shared pages list.
+                */
+               nr_pages = DIV_ROUND_UP(__end_bss_decrypted - __start_bss_decrypted,
+                                       PAGE_SIZE);
+               early_set_mem_enc_dec_hypercall((unsigned long)__start_bss_decrypted,
+                                               nr_pages, 0);
+
+               /*
+                * If not booted using EFI, enable Live migration support.
+                */
+               if (!efi_enabled(EFI_BOOT))
+                       wrmsrl(MSR_KVM_MIGRATION_CONTROL,
+                              KVM_MIGRATION_READY);
+       }
        kvmclock_init();
        x86_platform.apic_post_init = kvm_apic_init;
 }

diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index 455ac48..2673a89 100644 (file)
--- a/arch/x86/mm/mem_encrypt.c
+++ b/arch/x86/mm/mem_encrypt.c
@@ -409,6 +409,11 @@ int __init early_set_memory_encrypted(unsigned long vaddr, unsigned long size)
        return early_set_memory_enc_dec(vaddr, size, true);
 }
 
+void __init early_set_mem_enc_dec_hypercall(unsigned long vaddr, int npages, bool enc)
+{
+       notify_range_enc_status_changed(vaddr, npages, enc);
+}
+
 /*
  * SME and SEV are very similar but they are not the same, so there are
  * times that the kernel will need to distinguish between SME and SEV. The