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arch/x86_64: do not modify CR8 in interrupt path

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Currently, the interrupt service code manually raises the CPU task
priority to the priority level of the vector being serviced to defer
any lower-priority interrupts. This is unnecessary; the local APIC
is aware that an interrupt is in-service and accounts for its priority
when deciding whether to issue an overriding interrupt to the CPU.

Signed-off-by: Charles E. Youse <charles@gnuless.org>
This commit is contained in:
Charles E. Youse 2019-08-15 08:56:43 -07:00 • committed by Anas Nashif
commit 37929b3428
1 changed files with 2 additions and 13 deletions
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15
arch/x86_64/core/xuk.c
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@ -176,15 +176,7 @@ long _isr_c_top(unsigned long vecret, unsigned long rsp,
z_isr_entry();
/* Set current priority in CR8 to the currently-serviced IRQ
* and re-enable interrupts
*/
unsigned long long cr8, cr8new = vector >> 4;
__asm__ volatile("movq %%cr8, %0;"
"movq %1, %%cr8;"
"sti"
: "=r"(cr8) : "r"(cr8new));
__asm__ volatile("sti"); /* re-enable interrupts */
if (h->fn) {
h->fn(h->arg, err);
@ -192,10 +184,7 @@ long _isr_c_top(unsigned long vecret, unsigned long rsp,
z_unhandled_vector(vector, err, frame);
}
/* Mask interrupts to finish processing (they'll get restored
* in the upcoming IRET) and restore CR8
*/
__asm__ volatile("cli; movq %0, %%cr8" : : "r"(cr8));
__asm__ volatile("cli"); /* mask [at least] until upcoming IRET */
/* Signal EOI if it's an APIC-managed interrupt */
if (vector > 0x1f) {