@@ -409,27 +409,28 @@ void intel_posted_msi_init(void)
*/
static __always_inline bool handle_pending_pir(u64 *pir, struct pt_regs *regs)
{
+ unsigned long pir_copy[4], pending = 0;
int i, vec = FIRST_EXTERNAL_VECTOR;
- unsigned long pir_copy[4];
- bool handled = false;
- for (i = 0; i < 4; i++)
+ for (i = 0; i < 4; i++) {
pir_copy[i] = READ_ONCE(pir[i]);
+ pending |= pir_copy[i];
+ }
+
+ if (!pending)
+ return false;
for (i = 0; i < 4; i++) {
if (!pir_copy[i])
continue;
pir_copy[i] = arch_xchg(&pir[i], 0);
- handled = true;
}
- if (handled) {
- for_each_set_bit_from(vec, pir_copy, FIRST_SYSTEM_VECTOR)
- call_irq_handler(vec, regs);
- }
+ for_each_set_bit_from(vec, pir_copy, FIRST_SYSTEM_VECTOR)
+ call_irq_handler(vec, regs);
- return handled;
+ return true;
}
/*
Track whether or not at least one IRQ was found in PIR during the initial loop to load PIR chunks from memory. Doing so generates slightly better code (arguably) for processing the for-loop of XCHGs, especially for the case where there are no pending IRQs. Note, while PIR can be modified between the initial load and the XCHG, it can only _gain_ new IRQs, i.e. there is no danger of a false positive due to the final version of pir_copy[] being empty. Opportunistically convert the boolean to an "unsigned long" and compute the effective boolean result via bitwise-OR. Some compilers, e.g. clang-14, need the extra "hint" to elide conditional branches. Opportunistically rename the variable in anticipation of moving the PIR accesses to a common helper that can be shared by posted MSIs and KVM. Old: <+74>: test %rdx,%rdx <+77>: je 0xffffffff812bbeb0 <handle_pending_pir+144> <pir[0]> <+88>: mov $0x1,%dl> <+90>: test %rsi,%rsi <+93>: je 0xffffffff812bbe8c <handle_pending_pir+108> <pir[1]> <+106>: mov $0x1,%dl <+108>: test %rcx,%rcx <+111>: je 0xffffffff812bbe9e <handle_pending_pir+126> <pir[2]> <+124>: mov $0x1,%dl <+126>: test %rax,%rax <+129>: je 0xffffffff812bbeb9 <handle_pending_pir+153> <pir[3]> <+142>: jmp 0xffffffff812bbec1 <handle_pending_pir+161> <+144>: xor %edx,%edx <+146>: test %rsi,%rsi <+149>: jne 0xffffffff812bbe7f <handle_pending_pir+95> <+151>: jmp 0xffffffff812bbe8c <handle_pending_pir+108> <+153>: test %dl,%dl <+155>: je 0xffffffff812bbf8e <handle_pending_pir+366> New: <+74>: mov %rax,%r8 <+77>: or %rcx,%r8 <+80>: or %rdx,%r8 <+83>: or %rsi,%r8 <+86>: setne %bl <+89>: je 0xffffffff812bbf88 <handle_pending_pir+360> <+95>: test %rsi,%rsi <+98>: je 0xffffffff812bbe8d <handle_pending_pir+109> <pir[0]> <+109>: test %rdx,%rdx <+112>: je 0xffffffff812bbe9d <handle_pending_pir+125> <pir[1]> <+125>: test %rcx,%rcx <+128>: je 0xffffffff812bbead <handle_pending_pir+141> <pir[2]> <+141>: test %rax,%rax <+144>: je 0xffffffff812bbebd <handle_pending_pir+157> <pir[3]> Signed-off-by: Sean Christopherson <seanjc@google.com> --- arch/x86/kernel/irq.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-)