[PATCH v2 RESEND] x86/asm: Force native_apic_mem_read to use mov

From: Adam Dunlap
Date: Thu Sep 08 2022 - 13:05:31 EST


Previously, when compiled with clang, native_apic_mem_read gets inlined
into __xapic_wait_icr_idle and optimized to a testl instruction. When
run in a VM with SEV-ES enabled, it attempts to emulate this
instruction, but the emulator does not support it. Instead, use inline
assembly to force native_apic_mem_read to use the mov instruction which
is supported by the emulator.

Signed-off-by: Adam Dunlap <acdunlap@xxxxxxxxxx>
---
V1 -> V2: Replaced asm with readl function which does the same thing

arch/x86/include/asm/apic.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index 3415321c8240..b4c9034aa073 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -12,6 +12,7 @@
#include <asm/mpspec.h>
#include <asm/msr.h>
#include <asm/hardirq.h>
+#include <asm/io.h>

#define ARCH_APICTIMER_STOPS_ON_C3 1

@@ -109,7 +110,7 @@ static inline void native_apic_mem_write(u32 reg, u32 v)

static inline u32 native_apic_mem_read(u32 reg)
{
- return *((volatile u32 *)(APIC_BASE + reg));
+ return readl((void __iomem *)(APIC_BASE + reg));
}

extern void native_apic_wait_icr_idle(void);
--
2.37.1.559.g78731f0fdb-goog