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s390/pci: do not require AIS facility

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As of today QEMU does not provide the AIS facility to its guest.  This
prevents Linux guests from using PCI devices as the ais facility is
checked during init. As this is just a performance optimization, we can
move the ais check into the code where we need it (calling the SIC
instruction). This is used at initialization and on interrupt. Both
places do not require any serialization, so we can simply skip the
instruction.

Since we will now get all interrupts, we can also avoid the 2nd scan.
As we can have multiple interrupts in parallel we might trigger spurious
irqs more often for the non-AIS case but the core code can handle that.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Pierre Morel <pmorel@linux.vnet.ibm.com>
Reviewed-by: Halil Pasic <pasic@linux.vnet.ibm.com>
Acked-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
This commit is contained in:
Christian Borntraeger
2017-10-30 14:38:58 +01:00
committed by Heiko Carstens
parent 30e8eb8671
commit 48070c7305
3 changed files with 9 additions and 4 deletions
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6
arch/s390/pci/pci_insn.c
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@@ -7,6 +7,7 @@
#include <linux/export.h>
#include <linux/errno.h>
#include <linux/delay.h>
#include <asm/facility.h>
#include <asm/pci_insn.h>
#include <asm/pci_debug.h>
#include <asm/processor.h>
@@ -91,11 +92,14 @@ int zpci_refresh_trans(u64 fn, u64 addr, u64 range)
}
/* Set Interruption Controls */
void zpci_set_irq_ctrl(u16 ctl, char *unused, u8 isc)
int zpci_set_irq_ctrl(u16 ctl, char *unused, u8 isc)
{
if (!test_facility(72))
return -EIO;
asm volatile (
" .insn rsy,0xeb00000000d1,%[ctl],%[isc],%[u]\n"
: : [ctl] "d" (ctl), [isc] "d" (isc << 27), [u] "Q" (*unused));
return 0;
}
/* PCI Load */