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[PATCH] x86/amd: Fix DE_CFG truncation in amd_check_zenbleed()
- To: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- Date: Fri, 28 Jul 2023 19:17:30 +0100
- Authentication-results: esa3.hc3370-68.iphmx.com; dkim=none (message not signed) header.i=none
- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>
- Delivery-date: Fri, 28 Jul 2023 18:17:45 +0000
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- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
This line:
val &= ~chickenbit;
ends up truncating val to 32 bits, and turning off various errata workarounds
in Zen2 systems.
Fixes: f91c5ea97067 ("x86/amd: Mitigations for Zenbleed")
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>
The choice is between int or uint64_t. This is one case where the insistence
on using unsigned int as a default data type is genuinely unsafe.
---
xen/arch/x86/cpu/amd.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/xen/arch/x86/cpu/amd.c b/xen/arch/x86/cpu/amd.c
index 3ed06f670491..089038bf62c5 100644
--- a/xen/arch/x86/cpu/amd.c
+++ b/xen/arch/x86/cpu/amd.c
@@ -909,8 +909,9 @@ void __init detect_zen2_null_seg_behaviour(void)
void amd_check_zenbleed(void)
{
const struct cpu_signature *sig = &this_cpu(cpu_sig);
- unsigned int good_rev, chickenbit = (1 << 9);
+ unsigned int good_rev;
uint64_t val, old_val;
+ int chickenbit = (1 << 9);
/*
* If we're virtualised, we can't do family/model checks safely, and
--
2.30.2
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