Define apic_page construct to unionize APIC register 32bit/64bit
accesses and use it in apic_{get|set}*() to avoid using type
casting.
As Secure AVIC APIC driver requires accessing APIC page at byte
offsets (to get an APIC register's bitmap start address), support
byte access granularity in apic_page (in addition to 32-bit and
64-bit accesses).
One caveat of this change is that the generated code is slighly
larger. Below is the code generation for apic_get_reg() using
gcc-14.2:
- Without change:
apic_get_reg:
89 f6 mov %esi,%esi
8b 04 37 mov (%rdi,%rsi,1),%eax
c3 ret
- With change:
apic_get_reg:
c1 ee 02 shr $0x2,%esi
8b 04 b7 mov (%rdi,%rsi,4),%eax
c3 ret
lapic.o text size change is shown below:
Obj Old-size New-size
lapic.o 28800 28832
Signed-off-by: Neeraj Upadhyay <Neeraj.Upadhyay@xxxxxxx>
---
Changes since v7:
- Commit log update.
arch/x86/include/asm/apic.h | 25 +++++++++++++++++++++----
1 file changed, 21 insertions(+), 4 deletions(-)
diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index 07ba4935e873..b7cbe9ba363e 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -525,26 +525,43 @@ static inline int apic_find_highest_vector(void *bitmap)
return -1;
}
+struct apic_page {
+ union {
+ u64 regs64[PAGE_SIZE / 8];
+ u32 regs[PAGE_SIZE / 4];
+ u8 bytes[PAGE_SIZE];
+ };
+} __aligned(PAGE_SIZE);
+
static inline u32 apic_get_reg(void *regs, int reg)
{
- return *((u32 *) (regs + reg));
+ struct apic_page *ap = regs;
+
+ return ap->regs[reg / 4];
}
static inline void apic_set_reg(void *regs, int reg, u32 val)
{
- *((u32 *) (regs + reg)) = val;
+ struct apic_page *ap = regs;
+
+ ap->regs[reg / 4] = val;
}
static __always_inline u64 apic_get_reg64(void *regs, int reg)
{
+ struct apic_page *ap = regs;
+
BUILD_BUG_ON(reg != APIC_ICR);
- return *((u64 *) (regs + reg));
+
+ return ap->regs64[reg / 8];
}
static __always_inline void apic_set_reg64(void *regs, int reg, u64 val)
{
+ struct apic_page *ap = regs;
+
BUILD_BUG_ON(reg != APIC_ICR);
- *((u64 *) (regs + reg)) = val;
+ ap->regs64[reg / 8] = val;
}
static inline void apic_clear_vector(int vec, void *bitmap)
--
2.34.1
