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From 6b19062226ecebf63d2d0b0ff05b5bcfa7a05818 Mon Sep 17 00:00:00 2001
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From: Thomas Huth <thuth@redhat.com>
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Date: Thu, 10 Dec 2020 08:32:40 -0500
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Subject: [PATCH 4/5] pc-bios: s390x: Ensure Read IPL memory is clean
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RH-Author: Thomas Huth <thuth@redhat.com>
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Message-id: <20201210083241.173509-4-thuth@redhat.com>
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Patchwork-id: 100372
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O-Subject: [RHEL-8.4.0 qemu-kvm PATCH 3/4] pc-bios: s390x: Ensure Read IPL memory is clean
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Bugzilla: 1903135
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RH-Acked-by: Cornelia Huck <cohuck@redhat.com>
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RH-Acked-by: Jens Freimann <jfreimann@redhat.com>
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RH-Acked-by: David Hildenbrand <david@redhat.com>
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From: Eric Farman <farman@linux.ibm.com>
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If, for example, we boot off a virtio device and chreipl to a vfio-ccw
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device, the space at lowcore will be non-zero. We build a Read IPL CCW
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at address zero, but it will have leftover PSW data that will conflict
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with the Format-0 CCW being generated:
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0x0: 00080000 80010000
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------ Ccw0.cda
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-- Ccw0.chainData
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-- Reserved bits
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The data address will be overwritten with the correct value (0x0), but
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the apparent data chain bit will cause subsequent memory to be used as
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the target of the data store, which may not be where we expect (0x0).
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Clear out this space when we boot from DASD, so that we know it exists
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exactly as we expect.
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Signed-off-by: Eric Farman <farman@linux.ibm.com>
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Reviewed-by: Jason J. Herne <jjherne@linux.ibm.com>
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Reviewed-by: Janosch Frank <frankja@de.ibm.com>
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Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
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Acked-by: Cornelia Huck <cohuck@redhat.com>
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Message-Id: <20201120160117.59366-2-farman@linux.ibm.com>
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Signed-off-by: Thomas Huth <thuth@redhat.com>
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(cherry picked from commit d8e5bbdd0d6fa8d9b5ac15de62c87105d92ff558)
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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---
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pc-bios/s390-ccw/dasd-ipl.c | 3 +++
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1 file changed, 3 insertions(+)
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diff --git a/pc-bios/s390-ccw/dasd-ipl.c b/pc-bios/s390-ccw/dasd-ipl.c
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index 0fc879bb8e8..71cbae2f16e 100644
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--- a/pc-bios/s390-ccw/dasd-ipl.c
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+++ b/pc-bios/s390-ccw/dasd-ipl.c
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@@ -100,6 +100,9 @@ static void make_readipl(void)
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{
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Ccw0 *ccwIplRead = (Ccw0 *)0x00;
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+ /* Clear out any existing data */
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+ memset(ccwIplRead, 0, sizeof(Ccw0));
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+
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/* Create Read IPL ccw at address 0 */
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ccwIplRead->cmd_code = CCW_CMD_READ_IPL;
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ccwIplRead->cda = 0x00; /* Read into address 0x00 in main memory */
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--
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2.27.0
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