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authorTakashi Iwai <tiwai@suse.de>2019-09-10 14:03:08 +0300
committerTakashi Iwai <tiwai@suse.de>2019-09-10 14:03:08 +0300
commit7711fb7dac1ab77fd1b4d948f4647a569e4a1ae2 (patch)
treedd35ad21e0eb13572757dab279ae41f6d953baed /Documentation/virt/kvm/s390-diag.txt
parent789492f0c86505e63369907bcb1afdf52dec9366 (diff)
parentbb831786117519fc16dfd3eaa7b84e4f6bbb8d99 (diff)
downloadlinux-7711fb7dac1ab77fd1b4d948f4647a569e4a1ae2.tar.xz
Merge tag 'asoc-v5.4' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound into for-next
ASoC: Updates for v5.4 Quite a big update this time around, particularly in the core where we've had a lot of cleanups from Morimoto-san - there's not much functional change but quite a bit of modernization going on. We've also seen a lot of driver work, a lot of it cleanups but also some particular drivers. - Lots and lots of cleanups from Morimoto-san and Yue Haibing. - Lots of cleanups and enhancements to the Freescale, sunxi dnd Intel rivers. - Initial Sound Open Firmware suppot for i.MX8. - Removal of w90x900 and nuc900 drivers as the platforms are being removed. - New support for Cirrus Logic CS47L15 and CS47L92, Freescale i.MX 7ULP and 8MQ, Meson G12A and NXP UDA1334
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+The s390 DIAGNOSE call on KVM
+=============================
+
+KVM on s390 supports the DIAGNOSE call for making hypercalls, both for
+native hypercalls and for selected hypercalls found on other s390
+hypervisors.
+
+Note that bits are numbered as by the usual s390 convention (most significant
+bit on the left).
+
+
+General remarks
+---------------
+
+DIAGNOSE calls by the guest cause a mandatory intercept. This implies
+all supported DIAGNOSE calls need to be handled by either KVM or its
+userspace.
+
+All DIAGNOSE calls supported by KVM use the RS-a format:
+
+--------------------------------------
+| '83' | R1 | R3 | B2 | D2 |
+--------------------------------------
+0 8 12 16 20 31
+
+The second-operand address (obtained by the base/displacement calculation)
+is not used to address data. Instead, bits 48-63 of this address specify
+the function code, and bits 0-47 are ignored.
+
+The supported DIAGNOSE function codes vary by the userspace used. For
+DIAGNOSE function codes not specific to KVM, please refer to the
+documentation for the s390 hypervisors defining them.
+
+
+DIAGNOSE function code 'X'500' - KVM virtio functions
+-----------------------------------------------------
+
+If the function code specifies 0x500, various virtio-related functions
+are performed.
+
+General register 1 contains the virtio subfunction code. Supported
+virtio subfunctions depend on KVM's userspace. Generally, userspace
+provides either s390-virtio (subcodes 0-2) or virtio-ccw (subcode 3).
+
+Upon completion of the DIAGNOSE instruction, general register 2 contains
+the function's return code, which is either a return code or a subcode
+specific value.
+
+Subcode 0 - s390-virtio notification and early console printk
+ Handled by userspace.
+
+Subcode 1 - s390-virtio reset
+ Handled by userspace.
+
+Subcode 2 - s390-virtio set status
+ Handled by userspace.
+
+Subcode 3 - virtio-ccw notification
+ Handled by either userspace or KVM (ioeventfd case).
+
+ General register 2 contains a subchannel-identification word denoting
+ the subchannel of the virtio-ccw proxy device to be notified.
+
+ General register 3 contains the number of the virtqueue to be notified.
+
+ General register 4 contains a 64bit identifier for KVM usage (the
+ kvm_io_bus cookie). If general register 4 does not contain a valid
+ identifier, it is ignored.
+
+ After completion of the DIAGNOSE call, general register 2 may contain
+ a 64bit identifier (in the kvm_io_bus cookie case), or a negative
+ error value, if an internal error occurred.
+
+ See also the virtio standard for a discussion of this hypercall.
+
+
+DIAGNOSE function code 'X'501 - KVM breakpoint
+----------------------------------------------
+
+If the function code specifies 0x501, breakpoint functions may be performed.
+This function code is handled by userspace.
+
+This diagnose function code has no subfunctions and uses no parameters.