Implement a systemd service that runs a C program that extracts AMD SEV hardware parameters such as reduced-phys-bios and cbitpos from CPUID at boot time, verifies that SEV, SEV-ES & SEV-SNP are enabled, and outputs these details as JSON to /run/amd-sev-params.
Signed-off-by: Markus Frank <m.fr...@proxmox.com> --- Makefile | 1 + amd-sev-support/Makefile | 21 +++++++++++ amd-sev-support/amd-sev-support.c | 48 +++++++++++++++++++++++++ amd-sev-support/amd-sev-support.service | 12 +++++++ 4 files changed, 82 insertions(+) create mode 100644 amd-sev-support/Makefile create mode 100644 amd-sev-support/amd-sev-support.c create mode 100644 amd-sev-support/amd-sev-support.service diff --git a/Makefile b/Makefile index 133468d..ccd12a1 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 amd-sev-support install $(MAKE) -C qemu-configs install $(MAKE) -C vm-network-scripts install install -m 0755 qm $(DESTDIR)$(SBINDIR) diff --git a/amd-sev-support/Makefile b/amd-sev-support/Makefile new file mode 100644 index 0000000..022ed94 --- /dev/null +++ b/amd-sev-support/Makefile @@ -0,0 +1,21 @@ +DESTDIR= +PREFIX=/usr +SBINDIR=${PREFIX}/libexec/qemu-server +SERVICEDIR=/lib/systemd/system + +CC ?= gcc +CFLAGS += -O2 -fanalyzer -Werror -Wall -Wextra -Wpedantic -Wtype-limits -Wl,-z,relro -std=gnu11 + +amd-sev-support: amd-sev-support.c + $(CC) $(CFLAGS) -o $@ $< $(LDFLAGS) + +.PHONY: install +install: amd-sev-support + install -d ${DESTDIR}/${SBINDIR} + install -d ${DESTDIR}${SERVICEDIR} + install -m 0644 amd-sev-support.service ${DESTDIR}${SERVICEDIR} + install -m 0755 amd-sev-support ${DESTDIR}${SBINDIR} + +.PHONY: clean +clean: + rm -f amd-sev-support diff --git a/amd-sev-support/amd-sev-support.c b/amd-sev-support/amd-sev-support.c new file mode 100644 index 0000000..73a7bd8 --- /dev/null +++ b/amd-sev-support/amd-sev-support.c @@ -0,0 +1,48 @@ +#include <stdio.h> +#include <stdint.h> +#include <stdbool.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; + + FILE *file; + char *filename = "/run/amd-sev-params"; + + file = fopen(filename, "w"); + if (file == NULL) { + perror("Error opening file"); + return 1; + } + + fprintf(file, "{" + " \"cbitpos\": %u," + " \"reduced-phys-bits\": %u," + " \"sev\": %s," + " \"sev-es\": %s," + " \"sev-snp\": %s" + " }\n", + cbitpos, + reduced_phys_bits, + sev_support ? "true" : "false", + sev_es_support ? "true" : "false", + sev_snp_support ? "true" : "false" + ); + + fclose(file); + return 0; +} diff --git a/amd-sev-support/amd-sev-support.service b/amd-sev-support/amd-sev-support.service new file mode 100644 index 0000000..466dd0a --- /dev/null +++ b/amd-sev-support/amd-sev-support.service @@ -0,0 +1,12 @@ +[Unit] +Description=Read AMD SEV Parameters +RequiresMountsFor=/run +Before=pve-ha-lrm.service +Before=pve-guests.service + +[Service] +ExecStart=/usr/libexec/qemu-server/amd-sev-support +Type=forking + +[Install] +WantedBy=multi-user.target -- 2.39.2 _______________________________________________ pve-devel mailing list pve-devel@lists.proxmox.com https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel