qemu-kvm/SOURCES/kvm-vhost-Only-align-sections-for-vhost-user.patch

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From c35466c168e5219bf585aa65ac31fc9bdc7cbf36 Mon Sep 17 00:00:00 2001
From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Date: Fri, 24 Jan 2020 19:46:12 +0100
Subject: [PATCH 003/116] vhost: Only align sections for vhost-user
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
RH-Author: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-id: <20200124194613.41119-3-dgilbert@redhat.com>
Patchwork-id: 93452
O-Subject: [RHEL-AV-8.2 qemu-kvm PATCH 2/3] vhost: Only align sections for vhost-user
Bugzilla: 1779041
RH-Acked-by: Michael S. Tsirkin <mst@redhat.com>
RH-Acked-by: Vitaly Kuznetsov <vkuznets@redhat.com>
RH-Acked-by: Philippe Mathieu-Daudé <philmd@redhat.com>
From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
I added hugepage alignment code in c1ece84e7c9 to deal with
vhost-user + postcopy which needs aligned pages when using userfault.
However, on x86 the lower 2MB of address space tends to be shotgun'd
with small fragments around the 512-640k range - e.g. video RAM, and
with HyperV synic pages tend to sit around there - again splitting
it up. The alignment code complains with a 'Section rounded to ...'
error and gives up.
Since vhost-user already filters out devices without an fd
(see vhost-user.c vhost_user_mem_section_filter) it shouldn't be
affected by those overlaps.
Turn the alignment off on vhost-kernel so that it doesn't try
and align, and thus won't hit the rounding issues.
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <20200116202414.157959-3-dgilbert@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit 76525114736e8f669766e69b715fa59ce8648aae)
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
hw/virtio/vhost.c | 34 ++++++++++++++++++----------------
1 file changed, 18 insertions(+), 16 deletions(-)
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 774d87d..25fd469 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -547,26 +547,28 @@ static void vhost_region_add_section(struct vhost_dev *dev,
uintptr_t mrs_host = (uintptr_t)memory_region_get_ram_ptr(section->mr) +
section->offset_within_region;
RAMBlock *mrs_rb = section->mr->ram_block;
- size_t mrs_page = qemu_ram_pagesize(mrs_rb);
trace_vhost_region_add_section(section->mr->name, mrs_gpa, mrs_size,
mrs_host);
- /* Round the section to it's page size */
- /* First align the start down to a page boundary */
- uint64_t alignage = mrs_host & (mrs_page - 1);
- if (alignage) {
- mrs_host -= alignage;
- mrs_size += alignage;
- mrs_gpa -= alignage;
- }
- /* Now align the size up to a page boundary */
- alignage = mrs_size & (mrs_page - 1);
- if (alignage) {
- mrs_size += mrs_page - alignage;
- }
- trace_vhost_region_add_section_aligned(section->mr->name, mrs_gpa, mrs_size,
- mrs_host);
+ if (dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_USER) {
+ /* Round the section to it's page size */
+ /* First align the start down to a page boundary */
+ size_t mrs_page = qemu_ram_pagesize(mrs_rb);
+ uint64_t alignage = mrs_host & (mrs_page - 1);
+ if (alignage) {
+ mrs_host -= alignage;
+ mrs_size += alignage;
+ mrs_gpa -= alignage;
+ }
+ /* Now align the size up to a page boundary */
+ alignage = mrs_size & (mrs_page - 1);
+ if (alignage) {
+ mrs_size += mrs_page - alignage;
+ }
+ trace_vhost_region_add_section_aligned(section->mr->name, mrs_gpa, mrs_size,
+ mrs_host);
+ }
if (dev->n_tmp_sections) {
/* Since we already have at least one section, lets see if
--
1.8.3.1