[PATCH for 4.19 v4 01/10] tools/hvmloader: Fix non-deterministic cpuid()

[Alejandro Vallejo <alejandro.vallejo@xxxxxxxxx>]

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.

Signed-off-by: Alejandro Vallejo <alejandro.vallejo@xxxxxxxxx>
---
This is a fix for a latent bug. Should go into 4.19.

v4
  * New patch
---
 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 c34f077b38e3..d3b3f9038e64 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 deb823a892ef..3ad7c4f6d6a2 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 op,
+    uint32_t count,
+    uint32_t *eax,
+    uint32_t *ebx,
+    uint32_t *ecx,
+    uint32_t *edx)
+{
+    asm volatile ( "cpuid"
+          : "=a" (*eax), "=b" (*ebx), "=c" (*ecx), "=d" (*edx)
+          : "0" (op), "c" (count) );
+}
+
+/* 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)
-- 
2.34.1