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KVM VMX changes for 7.1

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- Drop obsolete (largely ignored by hardwre) branch hint prefixes from the
    VMX instruction macros, as saving a byte of code per instruction provides
    more benefits than the (mostly) superfluous prefixes.
 
  - Use ASM_INPUT_RM() in __vmcs_writel() to coerce clang into using a register
    input when appropriate.
 
  - Drop unnecessary parentheses in cpu_has_load_cet_ctrl() so as not to suggest
    that "return (x & y);" is KVM's preferred style.
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Merge tag 'kvm-x86-vmx-7.1' of https://github.com/kvm-x86/linux into HEAD

KVM VMX changes for 7.1

 - Drop obsolete (largely ignored by hardwre) branch hint prefixes from the
   VMX instruction macros, as saving a byte of code per instruction provides
   more benefits than the (mostly) superfluous prefixes.

 - Use ASM_INPUT_RM() in __vmcs_writel() to coerce clang into using a register
   input when appropriate.

 - Drop unnecessary parentheses in cpu_has_load_cet_ctrl() so as not to suggest
   that "return (x & y);" is KVM's preferred style.
This commit is contained in:
Paolo Bonzini 2026-04-13 12:49:36 +02:00
commit 7e7a6e2ad2
2 changed files with 2 additions and 5 deletions
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2
arch/x86/kvm/vmx/capabilities.h
View File

@ -107,7 +107,7 @@ static inline bool cpu_has_load_perf_global_ctrl(void)
static inline bool cpu_has_load_cet_ctrl(void)
{
return (vmcs_config.vmentry_ctrl & VM_ENTRY_LOAD_CET_STATE);
return vmcs_config.vmentry_ctrl & VM_ENTRY_LOAD_CET_STATE;
}
static inline bool cpu_has_save_perf_global_ctrl(void)

5
arch/x86/kvm/vmx/vmx_ops.h
View File

@ -119,7 +119,6 @@ static __always_inline unsigned long __vmcs_readl(unsigned long field)
#else /* !CONFIG_CC_HAS_ASM_GOTO_OUTPUT */
asm volatile("1: vmread %[field], %[output]\n\t"
".byte 0x3e\n\t" /* branch taken hint */
"ja 3f\n\t"
/*
@ -191,7 +190,6 @@ static __always_inline unsigned long vmcs_readl(unsigned long field)
#define vmx_asm1(insn, op1, error_args...) \
do { \
asm goto("1: " __stringify(insn) " %0\n\t" \
".byte 0x2e\n\t" /* branch not taken hint */ \
"jna %l[error]\n\t" \
_ASM_EXTABLE(1b, %l[fault]) \
: : op1 : "cc" : error, fault); \
@ -208,7 +206,6 @@ fault: \
#define vmx_asm2(insn, op1, op2, error_args...) \
do { \
asm goto("1: " __stringify(insn) " %1, %0\n\t" \
".byte 0x2e\n\t" /* branch not taken hint */ \
"jna %l[error]\n\t" \
_ASM_EXTABLE(1b, %l[fault]) \
: : op1, op2 : "cc" : error, fault); \
@ -224,7 +221,7 @@ fault: \
static __always_inline void __vmcs_writel(unsigned long field, unsigned long value)
{
vmx_asm2(vmwrite, "r"(field), "rm"(value), field, value);
vmx_asm2(vmwrite, "r" (field), ASM_INPUT_RM (value), field, value);
}
static __always_inline void vmcs_write16(unsigned long field, u16 value)