Re: [PATCH -next] RISC-V: KVM: optimize kvm_arch_hardware_enable()
From: chenlifu
Date: Mon Nov 21 2022 - 08:39:34 EST
在 2022/11/21 18:53, Andrew Jones 写道:
On Mon, Nov 21, 2022 at 08:39:15AM +0800, Chen Lifu wrote:
The values of CSR_HEDELEG and CSR_HIDELEG registers are constants,
so change them from variables to macros.
Signed-off-by: Chen Lifu <chenlifu@xxxxxxxxxx>
---
arch/riscv/kvm/main.c | 31 +++++++++++++------------------
1 file changed, 13 insertions(+), 18 deletions(-)
diff --git a/arch/riscv/kvm/main.c b/arch/riscv/kvm/main.c
index df2d8716851f..70196b03b6f9 100644
--- a/arch/riscv/kvm/main.c
+++ b/arch/riscv/kvm/main.c
@@ -12,10 +12,21 @@
#include <linux/kvm_host.h>
#include <asm/csr.h>
#include <asm/hwcap.h>
#include <asm/sbi.h>
+#define EXC_HEDELEG ((1UL << EXC_INST_MISALIGNED) | \
+ (1UL << EXC_BREAKPOINT) | \
+ (1UL << EXC_SYSCALL) | \
+ (1UL << EXC_INST_PAGE_FAULT) | \
+ (1UL << EXC_LOAD_PAGE_FAULT) | \
+ (1UL << EXC_STORE_PAGE_FAULT))
+
+#define IRQ_HIDELEG ((1UL << IRQ_VS_SOFT) | \
+ (1UL << IRQ_VS_TIMER) | \
+ (1UL << IRQ_VS_EXT))
+
long kvm_arch_dev_ioctl(struct file *filp,
unsigned int ioctl, unsigned long arg)
{
return -EINVAL;
}
@@ -30,29 +41,13 @@ int kvm_arch_hardware_setup(void *opaque)
return 0;
}
int kvm_arch_hardware_enable(void)
{
- unsigned long hideleg, hedeleg;
-
- hedeleg = 0;
- hedeleg |= (1UL << EXC_INST_MISALIGNED);
- hedeleg |= (1UL << EXC_BREAKPOINT);
- hedeleg |= (1UL << EXC_SYSCALL);
- hedeleg |= (1UL << EXC_INST_PAGE_FAULT);
- hedeleg |= (1UL << EXC_LOAD_PAGE_FAULT);
- hedeleg |= (1UL << EXC_STORE_PAGE_FAULT);
- csr_write(CSR_HEDELEG, hedeleg);
-
- hideleg = 0;
- hideleg |= (1UL << IRQ_VS_SOFT);
- hideleg |= (1UL << IRQ_VS_TIMER);
- hideleg |= (1UL << IRQ_VS_EXT);
- csr_write(CSR_HIDELEG, hideleg);
-
+ csr_write(CSR_HEDELEG, EXC_HEDELEG);
+ csr_write(CSR_HIDELEG, IRQ_HIDELEG);
csr_write(CSR_HCOUNTEREN, -1UL);
-
csr_write(CSR_HVIP, 0);
return 0;
}
--
2.37.1
I don't think this optimizes anything. I'm pretty sure the compiler will
load the input to csr_write() in the most efficient way it can, regardless
of using a constant or building the input out of constants. This could
maybe be considered a code cleanup, but, in this case, it's really in the
eye of the beholder.
Thanks,
drew
Thanks drew，you're right.
I compared two version arch/riscv/kvm/main.o files, they are same.