[PATCH v3 21/22] x86/sev: generate SEV kernel loader hashes in x86_load_linux

[Philippe Mathieu-Daudé <philmd@xxxxxxxxxx>]

From: Dov Murik <dovmurik@xxxxxxxxxxxxx>

If SEV is enabled and a kernel is passed via -kernel, pass the hashes of
kernel/initrd/cmdline in an encrypted guest page to OVMF for SEV
measured boot.

Co-developed-by: James Bottomley <jejb@xxxxxxxxxxxxx>
Signed-off-by: James Bottomley <jejb@xxxxxxxxxxxxx>
Signed-off-by: Dov Murik <dovmurik@xxxxxxxxxxxxx>
Reviewed-by: Daniel P. Berrangé <berrange@xxxxxxxxxx>
Message-Id: <20210930054915.13252-3-dovmurik@xxxxxxxxxxxxx>
[PMD: Rebased on top of 0021c4765a6]
Signed-off-by: Philippe Mathieu-Daudé <philmd@xxxxxxxxxx>
---
 hw/i386/x86.c | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/hw/i386/x86.c b/hw/i386/x86.c
index 41ef9a84a9f..0c7c054e3a0 100644
--- a/hw/i386/x86.c
+++ b/hw/i386/x86.c
@@ -47,6 +47,7 @@
 #include "hw/i386/fw_cfg.h"
 #include "hw/intc/i8259.h"
 #include "hw/rtc/mc146818rtc.h"
+#include "target/i386/sev_i386.h"
 
 #include "hw/acpi/cpu_hotplug.h"
 #include "hw/irq.h"
@@ -780,6 +781,7 @@ void x86_load_linux(X86MachineState *x86ms,
     const char *initrd_filename = machine->initrd_filename;
     const char *dtb_filename = machine->dtb;
     const char *kernel_cmdline = machine->kernel_cmdline;
+    SevKernelLoaderContext sev_load_ctx = {};
 
     /* Align to 16 bytes as a paranoia measure */
     cmdline_size = (strlen(kernel_cmdline) + 16) & ~15;
@@ -926,6 +928,8 @@ void x86_load_linux(X86MachineState *x86ms,
     fw_cfg_add_i32(fw_cfg, FW_CFG_CMDLINE_ADDR, cmdline_addr);
     fw_cfg_add_i32(fw_cfg, FW_CFG_CMDLINE_SIZE, strlen(kernel_cmdline) + 1);
     fw_cfg_add_string(fw_cfg, FW_CFG_CMDLINE_DATA, kernel_cmdline);
+    sev_load_ctx.cmdline_data = (char *)kernel_cmdline;
+    sev_load_ctx.cmdline_size = strlen(kernel_cmdline) + 1;
 
     if (protocol >= 0x202) {
         stl_p(header + 0x228, cmdline_addr);
@@ -1007,6 +1011,8 @@ void x86_load_linux(X86MachineState *x86ms,
         fw_cfg_add_i32(fw_cfg, FW_CFG_INITRD_ADDR, initrd_addr);
         fw_cfg_add_i32(fw_cfg, FW_CFG_INITRD_SIZE, initrd_size);
         fw_cfg_add_bytes(fw_cfg, FW_CFG_INITRD_DATA, initrd_data, initrd_size);
+        sev_load_ctx.initrd_data = initrd_data;
+        sev_load_ctx.initrd_size = initrd_size;
 
         stl_p(header + 0x218, initrd_addr);
         stl_p(header + 0x21c, initrd_size);
@@ -1065,15 +1071,32 @@ void x86_load_linux(X86MachineState *x86ms,
         load_image_size(dtb_filename, setup_data->data, dtb_size);
     }
 
-    memcpy(setup, header, MIN(sizeof(header), setup_size));
+    /*
+     * If we're starting an encrypted VM, it will be OVMF based, which uses the
+     * efi stub for booting and doesn't require any values to be placed in the
+     * kernel header.  We therefore don't update the header so the hash of the
+     * kernel on the other side of the fw_cfg interface matches the hash of the
+     * file the user passed in.
+     */
+    if (!sev_enabled()) {
+        memcpy(setup, header, MIN(sizeof(header), setup_size));
+    }
 
     fw_cfg_add_i32(fw_cfg, FW_CFG_KERNEL_ADDR, prot_addr);
     fw_cfg_add_i32(fw_cfg, FW_CFG_KERNEL_SIZE, kernel_size);
     fw_cfg_add_bytes(fw_cfg, FW_CFG_KERNEL_DATA, kernel, kernel_size);
+    sev_load_ctx.kernel_data = (char *)kernel;
+    sev_load_ctx.kernel_size = kernel_size;
 
     fw_cfg_add_i32(fw_cfg, FW_CFG_SETUP_ADDR, real_addr);
     fw_cfg_add_i32(fw_cfg, FW_CFG_SETUP_SIZE, setup_size);
     fw_cfg_add_bytes(fw_cfg, FW_CFG_SETUP_DATA, setup, setup_size);
+    sev_load_ctx.setup_data = (char *)setup;
+    sev_load_ctx.setup_size = setup_size;
+
+    if (sev_enabled()) {
+        sev_add_kernel_loader_hashes(&sev_load_ctx, &error_fatal);
+    }
 
     option_rom[nb_option_roms].bootindex = 0;
     option_rom[nb_option_roms].name = "linuxboot.bin";
-- 
2.31.1