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.vall...@cloud.com>
---
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
