119 lines
3.8 KiB
Diff
119 lines
3.8 KiB
Diff
From a5471559e7398418f1bb9c538a7bfc8f39e9ae98 Mon Sep 17 00:00:00 2001
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From: "Richard W.M. Jones" <rjones@redhat.com>
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Date: Fri, 4 Oct 2019 15:57:42 +0300
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Subject: [PATCH 18/21] Fix virt-what-cpuid-helper.
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The value returned in %eax is the max_entry (eg. 0x40000000
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if there are no further leafs). However it is not reliable.
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In addition if there are multiple leafs we should probably
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only print the highest one.
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Also use uint32_t instead of unsigned int.
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Thanks: Paolo Bonzini.
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---
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virt-what-cpuid-helper.c | 67 ++++++++++++++++++++++++++++------------
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1 file changed, 48 insertions(+), 19 deletions(-)
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diff --git a/virt-what-cpuid-helper.c b/virt-what-cpuid-helper.c
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index 7812545..0cd4a6f 100644
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--- a/virt-what-cpuid-helper.c
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+++ b/virt-what-cpuid-helper.c
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@@ -1,5 +1,5 @@
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/* virt-what-cpuid-helper: Are we running inside KVM or Xen HVM?
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- * Copyright (C) 2008 Red Hat Inc.
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+ * Copyright (C) 2008-2019 Red Hat Inc.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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@@ -21,14 +21,35 @@
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*/
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#include <stdio.h>
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+#include <stdlib.h>
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+#include <stdint.h>
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#include <string.h>
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#if defined(__i386__) || defined(__x86_64__)
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-static unsigned int
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-cpuid (unsigned int eax, char *sig)
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+/* Known x86 hypervisor signatures. Note that if you add a new test
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+ * to virt-what.in you may need to update this list. The signature is
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+ * always 12 bytes except in the case of KVM.
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+ */
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+static int
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+known_signature (char *sig)
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{
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- unsigned int *sig32 = (unsigned int *) sig;
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+ return
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+ strcmp (sig, "bhyve bhyve ") == 0 ||
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+ strcmp (sig, "KVMKVMKVM") == 0 ||
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+ strcmp (sig, "LKVMLKVMLKVM") == 0 ||
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+ strcmp (sig, "Microsoft Hv") == 0 ||
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+ strcmp (sig, "OpenBSDVMM58") == 0 ||
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+ strcmp (sig, "TCGTCGTCGTCG") == 0 ||
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+ strcmp (sig, "VMwareVMware") == 0 ||
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+ strcmp (sig, "XenVMMXenVMM") == 0 ||
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+ 0;
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+}
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+
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+static uint32_t
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+cpuid (uint32_t eax, char *sig)
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+{
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+ uint32_t *sig32 = (uint32_t *) sig;
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asm volatile (
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"xchgl %%ebx,%1; xor %%ebx,%%ebx; cpuid; xchgl %%ebx,%1"
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@@ -43,24 +64,32 @@ static void
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cpu_sig (void)
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{
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char sig[13];
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- unsigned int base = 0x40000000, leaf = base;
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- unsigned int max_entries;
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-
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- memset (sig, 0, sizeof sig);
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- max_entries = cpuid (leaf, sig);
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- puts (sig);
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+ const uint32_t base = 0x40000000;
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+ uint32_t leaf;
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- /* Most hypervisors only have information in leaf 0x40000000, but
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- * upstream Xen contains further leaf entries (in particular when
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- * used with Viridian [HyperV] extensions). CPUID is supposed to
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- * return the maximum leaf offset in %eax, so that's what we use,
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- * but only if it looks sensible.
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+ /* Most hypervisors only have information in leaf 0x40000000.
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+ *
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+ * Some hypervisors have "Viridian [HyperV] extensions", and those
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+ * must appear in slot 0x40000000, but they will also have the true
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+ * hypervisor in a higher slot.
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+ *
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+ * CPUID is supposed to return the maximum leaf offset in %eax, but
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+ * this is not reliable. Instead we check the returned signatures
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+ * against a known list (the others will be empty or garbage) and
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+ * only print the ones we know about. This is OK because if we add
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+ * a new test in virt-what we can update the list.
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+ *
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+ * By searching backwards we only print the highest entry, thus
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+ * ignoring Viridian for Xen (and Nutanix). If we ever encounter a
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+ * hypervisor that has more than 2 entries we may need to revisit
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+ * this.
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*/
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- if (max_entries > 3 && max_entries < 0x10000) {
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- for (leaf = base + 0x100; leaf <= base + max_entries; leaf += 0x100) {
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- memset (sig, 0, sizeof sig);
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- cpuid (leaf, sig);
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+ for (leaf = base + 0xff00; leaf >= base; leaf -= 0x100) {
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+ memset (sig, 0, sizeof sig);
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+ cpuid (leaf, sig);
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+ if (known_signature (sig)) {
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puts (sig);
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+ break;
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}
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}
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}
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--
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2.23.0
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