[xen staging] tools/hvmloader: Fix non-deterministic cpuid()

[patchbot@xxxxxxx]

commit cc47813c4a2c07a5c6c6a1491b98f3f8549835a7
Author:     Alejandro Vallejo <alejandro.vallejo@xxxxxxxxx>
AuthorDate: Tue Aug 13 16:39:10 2024 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Aug 13 16:39:10 2024 +0200

    tools/hvmloader: Fix non-deterministic cpuid()
    
    hvmloader's cpuid() implementation deviates from Xen's in that the value
    passed on ecx is unspecified. This means that when used on leaves that
    implement subleaves it's unspecified which one you get; though it's more
    than likely an invalid one.
    
    Import Xen's implementation so there are no surprises.
    
    Fixes: 318ac791f9f9 ("Add utilities needed for SMBIOS generation to 
hvmloader")
    Signed-off-by: Alejandro Vallejo <alejandro.vallejo@xxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 tools/firmware/hvmloader/util.c |  9 ---------
 tools/firmware/hvmloader/util.h | 27 ++++++++++++++++++++++++---
 2 files changed, 24 insertions(+), 12 deletions(-)

diff --git a/tools/firmware/hvmloader/util.c b/tools/firmware/hvmloader/util.c
index c34f077b38..d3b3f9038e 100644
--- a/tools/firmware/hvmloader/util.c
+++ b/tools/firmware/hvmloader/util.c
@@ -267,15 +267,6 @@ memcmp(const void *s1, const void *s2, unsigned n)
     return 0;
 }
 
-void
-cpuid(uint32_t idx, uint32_t *eax, uint32_t *ebx, uint32_t *ecx, uint32_t *edx)
-{
-    asm volatile (
-        "cpuid"
-        : "=a" (*eax), "=b" (*ebx), "=c" (*ecx), "=d" (*edx)
-        : "0" (idx) );
-}
-
 static const char hex_digits[] = "0123456789abcdef";
 
 /* Write a two-character hex representation of 'byte' to digits[].
diff --git a/tools/firmware/hvmloader/util.h b/tools/firmware/hvmloader/util.h
index deb823a892..17ed3783f2 100644
--- a/tools/firmware/hvmloader/util.h
+++ b/tools/firmware/hvmloader/util.h
@@ -184,9 +184,30 @@ int uart_exists(uint16_t uart_base);
 int lpt_exists(uint16_t lpt_base);
 int hpet_exists(unsigned long hpet_base);
 
-/* Do cpuid instruction, with operation 'idx' */
-void cpuid(uint32_t idx, uint32_t *eax, uint32_t *ebx,
-           uint32_t *ecx, uint32_t *edx);
+/* Some CPUID calls want 'count' to be placed in ecx */
+static inline void cpuid_count(
+    uint32_t leaf,
+    uint32_t subleaf,
+    uint32_t *eax,
+    uint32_t *ebx,
+    uint32_t *ecx,
+    uint32_t *edx)
+{
+    asm volatile ( "cpuid"
+                   : "=a" (*eax), "=b" (*ebx), "=c" (*ecx), "=d" (*edx)
+                   : "a" (leaf), "c" (subleaf) );
+}
+
+/* Generic CPUID function (subleaf 0) */
+static inline void cpuid(
+    uint32_t leaf,
+    uint32_t *eax,
+    uint32_t *ebx,
+    uint32_t *ecx,
+    uint32_t *edx)
+{
+    cpuid_count(leaf, 0, eax, ebx, ecx, edx);
+}
 
 /* Read the TSC register. */
 static inline uint64_t rdtsc(void)
--
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