169 lines
5.2 KiB
Diff
169 lines
5.2 KiB
Diff
From d8753fd5e71a4be0e99ecbbbfa052cb7bd90d717 Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= <berrange@redhat.com>
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Date: Fri, 7 Jul 2023 16:28:19 +0100
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Subject: [PATCH] efi: add helper API for detecting confidential virtualization
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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This helper is a simplified version of detect_confidential_virtualization()
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that merely returns a boolean status flag reflecting whether we are believed
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to be running inside a confidential VM.
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This flag can be used for turning off features that are inappropriate to
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use from a CVM, but must not be used for releasing sensitive data. The
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latter must only be done in response to an attestation for the environment.
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Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
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(cherry picked from commit b354a2cafc8ea38b4551aa3e4f078f1d7aa40c7c)
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Related: RHEL-50651
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---
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src/boot/efi/vmm.c | 117 +++++++++++++++++++++++++++++++++++++++++++++
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src/boot/efi/vmm.h | 2 +
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2 files changed, 119 insertions(+)
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diff --git a/src/boot/efi/vmm.c b/src/boot/efi/vmm.c
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index f9a59dca0a..214f8f7024 100644
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--- a/src/boot/efi/vmm.c
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+++ b/src/boot/efi/vmm.c
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@@ -7,6 +7,7 @@
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# include <cpuid.h>
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#endif
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+#include "confidential-virt-fundamental.h"
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#include "drivers.h"
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#include "efi-string.h"
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#include "string-util-fundamental.h"
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@@ -323,3 +324,119 @@ const char* smbios_find_oem_string(const char *name) {
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return NULL;
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}
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+
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+#if defined(__i386__) || defined(__x86_64__)
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+static uint32_t cpuid_leaf(uint32_t eax, char ret_sig[static 13], bool swapped) {
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+ /* zero-init as some queries explicitly require subleaf == 0 */
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+ uint32_t sig[3] = {};
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+
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+ if (swapped)
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+ __cpuid_count(eax, 0, eax, sig[0], sig[2], sig[1]);
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+ else
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+ __cpuid_count(eax, 0, eax, sig[0], sig[1], sig[2]);
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+
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+ memcpy(ret_sig, sig, sizeof(sig));
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+ ret_sig[12] = 0; /* \0-terminate the string to make string comparison possible */
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+
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+ return eax;
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+}
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+
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+static uint64_t msr(uint32_t index) {
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+ uint64_t val;
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+#ifdef __x86_64__
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+ uint32_t low, high;
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+ asm volatile ("rdmsr" : "=a"(low), "=d"(high) : "c"(index) : "memory");
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+ val = ((uint64_t)high << 32) | low;
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+#else
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+ asm volatile ("rdmsr" : "=A"(val) : "c"(index) : "memory");
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+#endif
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+ return val;
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+}
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+
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+static bool detect_hyperv_sev(void) {
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+ uint32_t eax, ebx, ecx, edx, feat;
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+ char sig[13] = {};
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+
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+ feat = cpuid_leaf(CPUID_HYPERV_VENDOR_AND_MAX_FUNCTIONS, sig, false);
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+
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+ if (feat < CPUID_HYPERV_MIN || feat > CPUID_HYPERV_MAX)
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+ return false;
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+
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+ if (memcmp(sig, CPUID_SIG_HYPERV, sizeof(sig)) != 0)
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+ return false;
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+
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+ __cpuid(CPUID_HYPERV_FEATURES, eax, ebx, ecx, edx);
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+
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+ if (ebx & CPUID_HYPERV_ISOLATION && !(ebx & CPUID_HYPERV_CPU_MANAGEMENT)) {
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+ __cpuid(CPUID_HYPERV_ISOLATION_CONFIG, eax, ebx, ecx, edx);
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+
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+ if ((ebx & CPUID_HYPERV_ISOLATION_TYPE_MASK) == CPUID_HYPERV_ISOLATION_TYPE_SNP)
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+ return true;
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+ }
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+
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+ return false;
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+}
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+
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+static bool detect_sev(void) {
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+ uint32_t eax, ebx, ecx, edx;
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+ uint64_t msrval;
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+
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+ __cpuid(CPUID_GET_HIGHEST_FUNCTION, eax, ebx, ecx, edx);
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+
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+ if (eax < CPUID_AMD_GET_ENCRYPTED_MEMORY_CAPABILITIES)
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+ return false;
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+
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+ __cpuid(CPUID_AMD_GET_ENCRYPTED_MEMORY_CAPABILITIES, eax, ebx, ecx, edx);
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+
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+ /* bit 1 == CPU supports SEV feature
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+ *
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+ * Note, Azure blocks this CPUID leaf from its SEV-SNP
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+ * guests, so we must fallback to trying some HyperV
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+ * specific CPUID checks.
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+ */
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+ if (!(eax & EAX_SEV))
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+ return detect_hyperv_sev();
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+
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+ msrval = msr(MSR_AMD64_SEV);
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+
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+ if (msrval & (MSR_SEV_SNP | MSR_SEV_ES | MSR_SEV))
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+ return true;
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+
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+ return false;
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+}
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+
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+static bool detect_tdx(void) {
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+ uint32_t eax, ebx, ecx, edx;
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+ char sig[13] = {};
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+
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+ __cpuid(CPUID_GET_HIGHEST_FUNCTION, eax, ebx, ecx, edx);
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+
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+ if (eax < CPUID_INTEL_TDX_ENUMERATION)
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+ return false;
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+
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+ cpuid_leaf(CPUID_INTEL_TDX_ENUMERATION, sig, true);
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+
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+ if (memcmp(sig, CPUID_SIG_INTEL_TDX, sizeof(sig)) == 0)
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+ return true;
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+
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+ return false;
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+}
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+#endif /* ! __i386__ && ! __x86_64__ */
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+
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+bool is_confidential_vm(void) {
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+#if defined(__i386__) || defined(__x86_64__)
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+ char sig[13] = {};
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+
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+ if (!cpuid_in_hypervisor())
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+ return false;
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+
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+ cpuid_leaf(0, sig, true);
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+
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+ if (memcmp(sig, CPUID_SIG_AMD, sizeof(sig)) == 0)
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+ return detect_sev();
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+ if (memcmp(sig, CPUID_SIG_INTEL, sizeof(sig)) == 0)
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+ return detect_tdx();
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+#endif /* ! __i386__ && ! __x86_64__ */
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+
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+ return false;
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+}
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diff --git a/src/boot/efi/vmm.h b/src/boot/efi/vmm.h
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index 2002f32bec..55c12039d2 100644
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--- a/src/boot/efi/vmm.h
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+++ b/src/boot/efi/vmm.h
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@@ -9,4 +9,6 @@ EFI_STATUS vmm_open(EFI_HANDLE *ret_qemu_dev, EFI_FILE **ret_qemu_dir);
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bool in_hypervisor(void);
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+bool is_confidential_vm(void);
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+
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const char* smbios_find_oem_string(const char *name);
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