[PATCH v10 15/16] KVM: x86: Add kexec support for SEV Live Migration.

[Ashish Kalra <Ashish.Kalra@amd.com>]

From: Ashish Kalra <ashish.kalra@amd.com>

Reset the host's shared pages list related to kernel
specific page encryption status settings before we load a
new kernel by kexec. We cannot reset the complete
shared pages list here as we need to retain the
UEFI/OVMF firmware specific settings.

The host's shared pages list is maintained for the
guest to keep track of all unencrypted guest memory regions,
therefore we need to explicitly mark all shared pages as
encrypted again before rebooting into the new guest kernel.

Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
---
 arch/x86/kernel/kvm.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index c4b8029c1442..d61156db7797 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -39,6 +39,7 @@
 #include <asm/cpuidle_haltpoll.h>
 #include <asm/ptrace.h>
 #include <asm/svm.h>
+#include <asm/e820/api.h>
 
 DEFINE_STATIC_KEY_FALSE(kvm_async_pf_enabled);
 
@@ -384,6 +385,33 @@ static void kvm_pv_guest_cpu_reboot(void *unused)
 	 */
 	if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
 		wrmsrl(MSR_KVM_PV_EOI_EN, 0);
+	/*
+	 * Reset the host's shared pages list related to kernel
+	 * specific page encryption status settings before we load a
+	 * new kernel by kexec. NOTE: We cannot reset the complete
+	 * shared pages list here as we need to retain the
+	 * UEFI/OVMF firmware specific settings.
+	 */
+	if (sev_live_migration_enabled & (smp_processor_id() == 0)) {
+		int i;
+		unsigned long nr_pages;
+
+		for (i = 0; i < e820_table->nr_entries; i++) {
+			struct e820_entry *entry = &e820_table->entries[i];
+			unsigned long start_pfn;
+			unsigned long end_pfn;
+
+			if (entry->type != E820_TYPE_RAM)
+				continue;
+
+			start_pfn = entry->addr >> PAGE_SHIFT;
+			end_pfn = (entry->addr + entry->size) >> PAGE_SHIFT;
+			nr_pages = DIV_ROUND_UP(entry->size, PAGE_SIZE);
+
+			kvm_sev_hypercall3(KVM_HC_PAGE_ENC_STATUS,
+					   entry->addr, nr_pages, 1);
+		}
+	}
 	kvm_pv_disable_apf();
 	kvm_disable_steal_time();
 }
-- 
2.17.1