crash: Disable SNP on crashkernel kexec

arch/x86/kernel/crash.c

@@ -25,6 +25,7 @@
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
 #include <linux/memblock.h>
+#include <linux/psp-sev.h>
 
 #include <asm/processor.h>
 #include <asm/hardirq.h>
@@ -131,6 +132,16 @@ void native_machine_crash_shutdown(struct pt_regs *regs)
 	/* The kernel is broken so disable interrupts */
 	local_irq_disable();
 
+	/*
+	 * Disable SEV/SNP to allow access to the reserved memory areas
+	 * including a normal IOMMU configuration
+	 * This needs to happen very early in the machine exit due to its
+	 * cross-cpu dependencies.
+	 */
+#ifdef CONFIG_AMD_SEV_SNP
+	sev_emergency_exit();
+#endif
+
 	crash_smp_send_stop();
 
 	/*

drivers/crypto/ccp/sev-dev.c

@@ -25,6 +25,7 @@
 #include <linux/fs.h>
 #include <linux/fs_struct.h>
 #include <linux/amd-iommu.h>
+#include <linux/crash_dump.h>
 
 #include <asm/smp.h>
 #include <asm/cacheflush.h>
@@ -2264,9 +2265,12 @@ int sev_dev_init(struct psp_device *psp)
 
 static void sev_firmware_shutdown(struct sev_device *sev)
 {
-	int error;
+	int error, rc;
 
-	sev_platform_shutdown(NULL);
+	rc = sev_platform_shutdown(&error);
+	if (rc)
+		dev_err(sev->dev, "SEV: failed to shutdown platform error 0x%#x, rc %d\n",
+			error, rc);
 
 	if (sev_es_tmr) {
 		/* The TMR area was encrypted, flush it from the cache */
@@ -2295,7 +2299,11 @@ static void sev_firmware_shutdown(struct sev_device *sev)
 	 */
 	free_snp_host_map(sev);
 
-	sev_snp_shutdown(&error);
+	rc = sev_snp_shutdown(&error);
+	if (rc)
+		dev_err(sev->dev, "SEV: failed to shutdown SEV/SNP error 0x%#x, rc %d\n",
+			error, rc);
+
 }
 
 void sev_dev_destroy(struct psp_device *psp)
@@ -2379,3 +2387,18 @@ void sev_pci_exit(void)
 
 	sev_firmware_shutdown(sev);
 }
+
+void sev_emergency_exit(void)
+{
+	struct sev_device *sev;
+
+	if (!psp_master)
+		return;
+
+	sev = psp_master->sev_data;
+
+	if (!sev)
+		return;
+
+	sev_firmware_shutdown(sev);
+}

include/linux/psp-sev.h

@@ -804,6 +804,14 @@ struct sev_data_snp_shutdown_ex {
  */
 int sev_platform_init(int *error);
 
+/**
+ * sev_emergency_exit - perform SEV and SNP deinitialization
+ *
+ * Intended for emergency situations like kernel crashes
+ * enableing kdump on the incoming kernel without running SEV/SNP
+ */
+void sev_emergency_exit(void);
+
 /**
  * sev_platform_status - perform SEV PLATFORM_STATUS command
  *