Implement a C program that extracts AMD SEV hardware information such
as reduced-phys-bios and cbitpos from CPUID at boot time, looks if
SEV, SEV-ES & SEV-SNP are enabled, and outputs these details as JSON
to /run/qemu-server/host-hw-capabilities.json
This programm can also be used to read and save other hardware
information at boot time.
Signed-off-by: Markus Frank <m.fr...@proxmox.com>
Co-authored-by: Thomas Lamprecht <t.lampre...@proxmox.com>
Tested-by: Filip Schauer <f.scha...@proxmox.com>
---
changes v11:
* removed systemd service
Makefile | 1 +
query-machine-capabilities/Makefile | 18 +++++
.../query-machine-capabilities.c | 79 +++++++++++++++++++
3 files changed, 98 insertions(+)
create mode 100644 query-machine-capabilities/Makefile
create mode 100644 query-machine-capabilities/query-machine-capabilities.c
diff --git a/Makefile b/Makefile
index 133468d..ed67fe0 100644
--- a/Makefile
+++ b/Makefile
@@ -65,6 +65,7 @@ install: $(PKGSOURCES)
install -m 0644 -D bootsplash.jpg $(DESTDIR)/usr/share/$(PACKAGE)
$(MAKE) -C PVE install
$(MAKE) -C qmeventd install
+ $(MAKE) -C query-machine-capabilities install
$(MAKE) -C qemu-configs install
$(MAKE) -C vm-network-scripts install
install -m 0755 qm $(DESTDIR)$(SBINDIR)
diff --git a/query-machine-capabilities/Makefile
b/query-machine-capabilities/Makefile
new file mode 100644
index 0000000..469c69f
--- /dev/null
+++ b/query-machine-capabilities/Makefile
@@ -0,0 +1,18 @@
+DESTDIR=
+PREFIX=/usr
+BINDIR=${PREFIX}/libexec/qemu-server
+
+CC ?= gcc
+CFLAGS += -O2 -fanalyzer -Werror -Wall -Wextra -Wpedantic -Wtype-limits
-Wl,-z,relro -std=gnu11
+
+query-machine-capabilities: query-machine-capabilities.c
+ $(CC) $(CFLAGS) -o $@ $< $(LDFLAGS)
+
+.PHONY: install
+install: query-machine-capabilities
+ install -d ${DESTDIR}/${BINDIR}
+ install -m 0755 query-machine-capabilities ${DESTDIR}${BINDIR}
+
+.PHONY: clean
+clean:
+ rm -f query-machine-capabilities
diff --git a/query-machine-capabilities/query-machine-capabilities.c
b/query-machine-capabilities/query-machine-capabilities.c
new file mode 100644
index 0000000..7640e38
--- /dev/null
+++ b/query-machine-capabilities/query-machine-capabilities.c
@@ -0,0 +1,79 @@
+#include <stdio.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <sys/stat.h>
+#include <errno.h>
+#include <string.h>
+
+int main() {
+ uint32_t eax, ebx, ecx, edx;
+
+ // query Encrypted Memory Capabilities, see:
+ //
https://en.wikipedia.org/wiki/CPUID#EAX=8000001Fh:_Encrypted_Memory_Capabilities
+ uint32_t query_function = 0x8000001F;
+ asm volatile("cpuid"
+ : "=a"(eax), "=b"(ebx), "=c"(ecx), "=d"(edx)
+ : "0"(query_function)
+ );
+
+ bool sev_support = (eax & (1<<1)) != 0;
+ bool sev_es_support = (eax & (1<<3)) != 0;
+ bool sev_snp_support = (eax & (1<<4)) != 0;
+
+ uint8_t cbitpos = ebx & 0x3f;
+ uint8_t reduced_phys_bits = (ebx >> 6) & 0x3f;
+
+ const char *path = "/run/qemu-server/";
+ // Check that the directory exists and create it if it does not.
+ struct stat statbuf;
+ int ret = stat(path, &statbuf);
+ if (ret == 0) {
+ if (!S_ISDIR(statbuf.st_mode)) {
+ printf("Path %s is not a directory.\n", path);
+ return 1;
+ }
+ } else if (errno == ENOENT) {
+ if (mkdir(path, 0755) != 0) {
+ printf("Error creating directory %s: %s\n", path, strerror(errno));
+ return 1;
+ }
+ } else {
+ printf("Error checking path %s: %s\n", path, strerror(errno));
+ return 1;
+ }
+
+ FILE *file;
+ const char *filename = "/run/qemu-server/host-hw-capabilities.json";
+ file = fopen(filename, "w");
+ if (file == NULL) {
+ perror("Error opening file");
+ return 1;
+ }
+
+ ret = fprintf(file,
+ "{"
+ " \"amd-sev\": {"
+ " \"cbitpos\": %u,"
+ " \"reduced-phys-bits\": %u,"
+ " \"sev-support\": %s,"
+ " \"sev-support-es\": %s,"
+ " \"sev-support-snp\": %s"
+ " }"
+ " }\n",
+ cbitpos,
+ reduced_phys_bits,
+ sev_support ? "true" : "false",
+ sev_es_support ? "true" : "false",
+ sev_snp_support ? "true" : "false"
+ );
+ if (ret == -1) {
+ printf("Error writing to file %s: %s\n", path, strerror(errno));
+ }
+
+ ret = fclose(file);
+ if (ret == -1) {
+ printf("Error closing file %s: %s\n", path, strerror(errno));
+ }
+
+ return 0;
+}
--
2.39.2
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