bhyve: add config option to load ACPI tables into memory

For backward compatibility, the ACPI tables are loaded into the guest
memory. Windows scans the memory, finds the ACPI tables and uses them.
It ignores the ACPI tables provided by the UEFI. We are patching the
ACPI tables in the guest memory, so that's mostly fine. However, Windows
will break when the ACPI tables become to large or when we add entries
which can't be patched by bhyve. One example of an unpatchable entry, is
a TPM log. The TPM log has to be allocated by the guest firmware. As the
address of the TPM log is unpredictable, bhyve can't assign it in the
memory version of the ACPI tables. Additionally, this makes it
impossible for bhyve to calculate a correct checksum of the table.

By default ACPI tables are still loaded into guest memory for backward
compatibility. The new acpi_tables_in_memory config value can be set to
false to avoid this behaviour.

Reviewed by:		markj
MFC after:		1 week
Sponsored by:		Beckhoff Automation GmbH & Co. KG
Differential Revision:	https://reviews.freebsd.org/D39979

3 files changed, 46 insertions, 15 deletions

diff --git a/usr.sbin/bhyve/basl.c b/usr.sbin/bhyve/basl.c
index 8a4f2c4f311e..c20a52571937 100644
--- a/usr.sbin/bhyve/basl.c
+++ b/usr.sbin/bhyve/basl.c
@@ -20,6 +20,7 @@
 #include <vmmapi.h>
 
 #include "basl.h"
+#include "config.h"
 #include "qemu_loader.h"
 
 struct basl_table_checksum {
@@ -60,6 +61,7 @@ static STAILQ_HEAD(basl_table_list, basl_table) basl_tables = STAILQ_HEAD_INITIA
 static struct qemu_loader *basl_loader;
 static struct basl_table *rsdt;
 static struct basl_table *xsdt;
+static bool load_into_memory;
 
 static __inline uint64_t
 basl_le_dec(void *pp, size_t len)
@@ -153,6 +155,16 @@ basl_finish_install_guest_tables(struct basl_table *const table, uint32_t *const
 		return (EFAULT);
 	}
 
+	/* Cause guest BIOS to copy the ACPI table into guest memory. */
+	BASL_EXEC(
+	    qemu_fwcfg_add_file(table->fwcfg_name, table->len, table->data));
+	BASL_EXEC(qemu_loader_alloc(basl_loader, table->fwcfg_name,
+	    table->alignment, QEMU_LOADER_ALLOC_HIGH));
+
+	if (!load_into_memory) {
+		return (0);
+	}
+
 	/*
 	 * Install ACPI tables directly in guest memory for use by guests which
 	 * do not boot via EFI. EFI ROMs provide a pointer to the firmware
@@ -168,12 +180,6 @@ basl_finish_install_guest_tables(struct basl_table *const table, uint32_t *const
 	}
 	memcpy(gva, table->data, table->len);
 
-	/* Cause guest bios to copy the ACPI table into guest memory. */
-	BASL_EXEC(
-	    qemu_fwcfg_add_file(table->fwcfg_name, table->len, table->data));
-	BASL_EXEC(qemu_loader_alloc(basl_loader, table->fwcfg_name,
-	    table->alignment, QEMU_LOADER_ALLOC_HIGH));
-
 	return (0);
 }
 
@@ -197,6 +203,14 @@ basl_finish_patch_checksums(struct basl_table *const table)
 		assert(checksum->start < table->len);
 		assert(checksum->start + len <= table->len);
 
+		/* Cause guest BIOS to patch the checksum. */
+		BASL_EXEC(qemu_loader_add_checksum(basl_loader,
+		    table->fwcfg_name, checksum->off, checksum->start, len));
+
+		if (!load_into_memory) {
+			continue;
+		}
+
 		/*
 		 * Install ACPI tables directly in guest memory for use by
 		 * guests which do not boot via EFI. EFI ROMs provide a pointer
@@ -230,10 +244,6 @@ basl_finish_patch_checksums(struct basl_table *const table)
 			sum += *(gva + i);
 		}
 		*checksum_gva = -sum;
-
-		/* Cause guest bios to patch the checksum. */
-		BASL_EXEC(qemu_loader_add_checksum(basl_loader,
-		    table->fwcfg_name, checksum->off, checksum->start, len));
 	}
 
 	return (0);
@@ -278,6 +288,15 @@ basl_finish_patch_pointers(struct basl_table *const table)
 			return (EFAULT);
 		}
 
+		/* Cause guest BIOS to patch the pointer. */
+		BASL_EXEC(
+		    qemu_loader_add_pointer(basl_loader, table->fwcfg_name,
+			src_table->fwcfg_name, pointer->off, pointer->size));
+
+		if (!load_into_memory) {
+			continue;
+		}
+
 		/*
 		 * Install ACPI tables directly in guest memory for use by
 		 * guests which do not boot via EFI. EFI ROMs provide a pointer
@@ -301,11 +320,6 @@ basl_finish_patch_pointers(struct basl_table *const table)
 		val = basl_le_dec(gva + pointer->off, pointer->size);
 		val += BHYVE_ACPI_BASE + src_table->off;
 		basl_le_enc(gva + pointer->off, val, pointer->size);
-
-		/* Cause guest bios to patch the pointer. */
-		BASL_EXEC(
-		    qemu_loader_add_pointer(basl_loader, table->fwcfg_name,
-			src_table->fwcfg_name, pointer->off, pointer->size));
 	}
 
 	return (0);
@@ -339,6 +353,15 @@ basl_finish(void)
 	}
 
 	/*
+	 * If we install ACPI tables by FwCfg and by memory, Windows will use
+	 * the tables from memory. This can cause issues when using advanced
+	 * features like a TPM log because we aren't able to patch the memory
+	 * tables accordingly.
+	 */
+	load_into_memory = get_config_bool_default("acpi_tables_in_memory",
+	    true);
+
+	/*
 	 * We have to install all tables before we can patch them. Therefore,
 	 * use two loops. The first one installs all tables and the second one
 	 * patches them.
diff --git a/usr.sbin/bhyve/bhyve_config.5 b/usr.sbin/bhyve/bhyve_config.5
index d074d4503894..6904ad096c0d 100644
--- a/usr.sbin/bhyve/bhyve_config.5
+++ b/usr.sbin/bhyve/bhyve_config.5
@@ -122,6 +122,13 @@ The value must be formatted as described in
 Wire guest memory.
 .It Va acpi_tables Ta bool Ta false Ta
 Generate ACPI tables.
+.It Va acpi_tables_in_memory Ta bool Ta true Ta
+.Xr bhyve 8
+always exposes ACPI tables by FwCfg.
+For backward compatibility bhyve copies them into the guest memory as well.
+This can cause problems if the guest uses the in-memory version, since certain
+advanced features, such as TPM emulation, are exposed only via FwCfg.
+Therefore, it is recommended to set this flag to false when running Windows guests.
 .It Va destroy_on_poweroff Ta bool Ta false Ta
 Destroy the VM on guest-initiated power-off.
 .It Va gdb.address Ta string Ta localhost Ta
diff --git a/usr.sbin/bhyve/bhyverun.c b/usr.sbin/bhyve/bhyverun.c
index 3d32bfd35408..3db796c65a28 100644
--- a/usr.sbin/bhyve/bhyverun.c
+++ b/usr.sbin/bhyve/bhyverun.c
@@ -1202,6 +1202,7 @@ set_defaults(void)
 {
 
 	set_config_bool("acpi_tables", false);
+	set_config_bool("acpi_tables_in_memory", true);
 	set_config_value("memory.size", "256M");
 	set_config_bool("x86.strictmsr", true);
 	set_config_value("lpc.fwcfg", "bhyve");