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From 60d903fbb7653bc9754228bdab4c6933fcda1e72 Mon Sep 17 00:00:00 2001
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From: "Richard W.M. Jones" <rjones@redhat.com>
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Date: Tue, 13 Apr 2021 09:35:07 +0100
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Subject: [PATCH] Simplify and fix invocation of cpuid.
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Fixes a crash on some platforms identified by Yongkui Guo in
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https://bugzilla.redhat.com/show_bug.cgi?id=1756381#c15
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---
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virt-what-cpuid-helper.c | 24 ++++++++++++++++--------
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1 file changed, 16 insertions(+), 8 deletions(-)
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diff --git a/virt-what-cpuid-helper.c b/virt-what-cpuid-helper.c
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index 9c6cdb2..fdceb62 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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@@ -47,17 +47,25 @@ known_signature (const char *sig)
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0;
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}
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+/* Copied from the Linux kernel definition in
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+ * arch/x86/include/asm/processor.h
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+ */
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+static inline void
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+cpuid (uint32_t *eax, uint32_t *ebx, uint32_t *ecx, uint32_t *edx)
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+{
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+ asm volatile ("cpuid"
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+ : "=a" (*eax), "=b" (*ebx), "=c" (*ecx), "=d" (*edx)
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+ : "0" (*eax), "2" (*ecx)
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+ : "memory");
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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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+cpuid_leaf (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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- : "=a" (eax), "+r" (sig32[0]), "=c" (sig32[1]), "=d" (sig32[2])
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- : "0" (eax));
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- sig[12] = 0;
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-
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+ cpuid (&eax, &sig32[0], &sig32[1], &sig32[2]);
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+ sig[12] = 0; /* \0-terminate the string to make string comparison possible */
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return eax;
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}
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@@ -87,7 +95,7 @@ cpu_sig (void)
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*/
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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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+ cpuid_leaf (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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2.29.0.rc2
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