We already have 3 cases using STIBP as a Zen1/2 heuristic, and are about to
introduce a 4th. Wrap the heuristic into a pair of predictes rather than
opencoding it, and the explaination of the heursitic, at each usage site.
Signed-off-by: Andrew Cooper <andrew.coop...@citrix.com>
---
CC: Jan Beulich <jbeul...@suse.com>
CC: Roger Pau Monné <roger....@citrix.com>
CC: Wei Liu <w...@xen.org>
v2:
* New
---
xen/arch/x86/cpu/amd.c | 18 ++++--------------
xen/arch/x86/include/asm/amd.h | 11 +++++++++++
2 files changed, 15 insertions(+), 14 deletions(-)
diff --git a/xen/arch/x86/cpu/amd.c b/xen/arch/x86/cpu/amd.c
index bbf7887f2e1d..4f27187f92ec 100644
--- a/xen/arch/x86/cpu/amd.c
+++ b/xen/arch/x86/cpu/amd.c
@@ -882,15 +882,13 @@ void amd_set_legacy_ssbd(bool enable)
* non-branch instructions to be ignored. It is to be set unilaterally in
* newer microcode.
*
- * This chickenbit is something unrelated on Zen1, and Zen1 vs Zen2 isn't a
- * simple model number comparison, so use STIBP as a heuristic to separate the
- * two uarches in Fam17h(AMD)/18h(Hygon).
+ * This chickenbit is something unrelated on Zen1.
*/
void amd_init_spectral_chicken(void)
{
uint64_t val, chickenbit = 1 << 1;
- if (cpu_has_hypervisor || !boot_cpu_has(X86_FEATURE_AMD_STIBP))
+ if (cpu_has_hypervisor || !is_zen2_uarch())
return;
if (rdmsr_safe(MSR_AMD64_DE_CFG2, val) == 0 && !(val & chickenbit))
@@ -939,11 +937,8 @@ void amd_check_zenbleed(void)
* With the Fam17h check above, most parts getting here are
* Zen1. They're not affected. Assume Zen2 ones making it
* here are affected regardless of microcode version.
- *
- * Zen1 vs Zen2 isn't a simple model number comparison, so use
- * STIBP as a heuristic to distinguish.
*/
- if (!boot_cpu_has(X86_FEATURE_AMD_STIBP))
+ if (is_zen1_uarch())
return;
good_rev = ~0U;
break;
@@ -1298,12 +1293,7 @@ static int __init cf_check zen2_c6_errata_check(void)
*/
s_time_t delta;
- /*
- * Zen1 vs Zen2 isn't a simple model number comparison, so use STIBP as
- * a heuristic to separate the two uarches in Fam17h.
- */
- if (cpu_has_hypervisor || boot_cpu_data.x86 != 0x17 ||
- !boot_cpu_has(X86_FEATURE_AMD_STIBP))
+ if (cpu_has_hypervisor || boot_cpu_data.x86 != 0x17 || !is_zen2_uarch())
return 0;
/*
diff --git a/xen/arch/x86/include/asm/amd.h b/xen/arch/x86/include/asm/amd.h
index 09ee52dc1c09..d862cb7972a1 100644
--- a/xen/arch/x86/include/asm/amd.h
+++ b/xen/arch/x86/include/asm/amd.h
@@ -140,6 +140,17 @@
AMD_MODEL_RANGE(0x11, 0x0, 0x0, 0xff, 0xf), \
AMD_MODEL_RANGE(0x12, 0x0, 0x0, 0xff, 0xf))
+/*
+ * The Zen1 and Zen2 microarchitectures are implemented by AMD (Fam17h) and
+ * Hygon (Fam18h) but without simple model number rules. Instead, use STIBP
+ * as a heuristic that distinguishes the two.
+ *
+ * The caller is required to perform the appropriate vendor/family checks
+ * first.
+ */
+#define is_zen1_uarch() (!boot_cpu_has(X86_FEATURE_AMD_STIBP))
+#define is_zen2_uarch() boot_cpu_has(X86_FEATURE_AMD_STIBP)
+
struct cpuinfo_x86;
int cpu_has_amd_erratum(const struct cpuinfo_x86 *, int, ...);
--
2.30.2
