[PATCH 4.9 086/107] x86/irq: Demote irq_cpustat_t::__softirq_pending to u16

From: Greg Kroah-Hartman
Date: Tue Aug 14 2018 - 13:44:09 EST

4.9-stable review patch. If anyone has any objections, please let me know.


From: Nicolai Stange <nstange@xxxxxxx>

commit 9aee5f8a7e30330d0a8f4c626dc924ca5590aba5 upstream

An upcoming patch will extend KVM's L1TF mitigation in conditional mode
to also cover interrupts after VMEXITs. For tracking those, stores to a
new per-cpu flag from interrupt handlers will become necessary.

In order to improve cache locality, this new flag will be added to x86's

Make some space available there by shrinking the ->softirq_pending bitfield
from 32 to 16 bits: the number of bits actually used is only NR_SOFTIRQS,
i.e. 10.

Suggested-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Nicolai Stange <nstange@xxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
arch/x86/include/asm/hardirq.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/include/asm/hardirq.h
+++ b/arch/x86/include/asm/hardirq.h
@@ -5,7 +5,7 @@
#include <linux/irq.h>

typedef struct {
- unsigned int __softirq_pending;
+ u16 __softirq_pending;
unsigned int __nmi_count; /* arch dependent */
unsigned int apic_timer_irqs; /* arch dependent */