This is a note to let you know that I've just added the patch titled

s390/pci: do not require AIS facility

to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: s390-pci-do-not-require-ais-facility.patch and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Wed Dec 6 16:43:17 CET 2017

From: Christian Borntraeger borntraeger@de.ibm.com Date: Mon, 30 Oct 2017 14:38:58 +0100 Subject: s390/pci: do not require AIS facility

From: Christian Borntraeger borntraeger@de.ibm.com

[ Upstream commit 48070c73058be6de9c0d754d441ed7092dfc8f12 ]

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 Signed-off-by: Sasha Levin alexander.levin@verizon.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/s390/include/asm/pci_insn.h | 2 +- arch/s390/pci/pci.c | 5 +++-- arch/s390/pci/pci_insn.c | 6 +++++- 3 files changed, 9 insertions(+), 4 deletions(-)

--- a/arch/s390/include/asm/pci_insn.h +++ b/arch/s390/include/asm/pci_insn.h @@ -81,6 +81,6 @@ int zpci_refresh_trans(u64 fn, u64 addr, int zpci_load(u64 *data, u64 req, u64 offset); int zpci_store(u64 data, u64 req, u64 offset); int zpci_store_block(const u64 *data, u64 req, u64 offset); -void zpci_set_irq_ctrl(u16 ctl, char *unused, u8 isc); +int zpci_set_irq_ctrl(u16 ctl, char *unused, u8 isc);

#endif --- a/arch/s390/pci/pci.c +++ b/arch/s390/pci/pci.c @@ -359,7 +359,8 @@ static void zpci_irq_handler(struct airq /* End of second scan with interrupts on. */ break; /* First scan complete, reenable interrupts. */ - zpci_set_irq_ctrl(SIC_IRQ_MODE_SINGLE, NULL, PCI_ISC); + if (zpci_set_irq_ctrl(SIC_IRQ_MODE_SINGLE, NULL, PCI_ISC)) + break; si = 0; continue; } @@ -921,7 +922,7 @@ static int __init pci_base_init(void) if (!s390_pci_probe) return 0;

- if (!test_facility(69) || !test_facility(71) || !test_facility(72)) + if (!test_facility(69) || !test_facility(71)) return 0;

rc = zpci_debug_init(); --- a/arch/s390/pci/pci_insn.c +++ b/arch/s390/pci/pci_insn.c @@ -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, }

/* 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 */

Patches currently in stable-queue which might be from borntraeger@de.ibm.com are

queue-4.4/s390-pci-do-not-require-ais-facility.patch