qemu-kvm/kvm-hw-arm-virt-Improve-high-memory-region-address-assig.patch

From 1c7fad3776a14ca35b24dc2fdb262d4ddf40d6eb Mon Sep 17 00:00:00 2001
From: Gavin Shan <gshan@redhat.com>
Date: Wed, 21 Dec 2022 08:48:45 +0800
Subject: [PATCH 5/8] hw/arm/virt: Improve high memory region address
 assignment

RH-Author: Gavin Shan <gshan@redhat.com>
RH-MergeRequest: 126: hw/arm/virt: Optimize high memory region address assignment
RH-Bugzilla: 2113840
RH-Acked-by: Eric Auger <eric.auger@redhat.com>
RH-Acked-by: Cornelia Huck <cohuck@redhat.com>
RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
RH-Commit: [5/8] 4d77fa78b5258a1bd8d30405cec5ba3311d42f92

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2113840

There are three high memory regions, which are VIRT_HIGH_REDIST2,
VIRT_HIGH_PCIE_ECAM and VIRT_HIGH_PCIE_MMIO. Their base addresses
are floating on highest RAM address. However, they can be disabled
in several cases.

(1) One specific high memory region is likely to be disabled by
    code by toggling vms->highmem_{redists, ecam, mmio}.

(2) VIRT_HIGH_PCIE_ECAM region is disabled on machine, which is
    'virt-2.12' or ealier than it.

(3) VIRT_HIGH_PCIE_ECAM region is disabled when firmware is loaded
    on 32-bits system.

(4) One specific high memory region is disabled when it breaks the
    PA space limit.

The current implementation of virt_set_{memmap, high_memmap}() isn't
optimized because the high memory region's PA space is always reserved,
regardless of whatever the actual state in the corresponding
vms->highmem_{redists, ecam, mmio} flag. In the code, 'base' and
'vms->highest_gpa' are always increased for case (1), (2) and (3).
It's unnecessary since the assigned PA space for the disabled high
memory region won't be used afterwards.

Improve the address assignment for those three high memory region by
skipping the address assignment for one specific high memory region if
it has been disabled in case (1), (2) and (3). The memory layout may
be changed after the improvement is applied, which leads to potential
migration breakage. So 'vms->highmem_compact' is added to control if
the improvement should be applied. For now, 'vms->highmem_compact' is
set to false, meaning that we don't have memory layout change until it
becomes configurable through property 'compact-highmem' in next patch.

Signed-off-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Tested-by: Zhenyu Zhang <zhenyzha@redhat.com>
Message-id: 20221029224307.138822-6-gshan@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
(cherry picked from commit 4a4ff9edc6a8fdc76082af5b41b059217138c09b)
Signed-off-by: Gavin Shan <gshan@redhat.com>
---
 hw/arm/virt.c         | 15 ++++++++++-----
 include/hw/arm/virt.h |  1 +
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 6e3b9fc060..6896e0ca0f 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -1768,18 +1768,23 @@ static void virt_set_high_memmap(VirtMachineState *vms,
         vms->memmap[i].size = region_size;
 
         /*
-         * Check each device to see if they fit in the PA space,
-         * moving highest_gpa as we go.
+         * Check each device to see if it fits in the PA space,
+         * moving highest_gpa as we go. For compatibility, move
+         * highest_gpa for disabled fitting devices as well, if
+         * the compact layout has been disabled.
          *
          * For each device that doesn't fit, disable it.
          */
         fits = (region_base + region_size) <= BIT_ULL(pa_bits);
-        if (fits) {
-            vms->highest_gpa = region_base + region_size - 1;
+        *region_enabled &= fits;
+        if (vms->highmem_compact && !*region_enabled) {
+            continue;
         }
 
-        *region_enabled &= fits;
         base = region_base + region_size;
+        if (fits) {
+            vms->highest_gpa = base - 1;
+        }
     }
 }
 
diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h
index 22b54ec510..15bd291311 100644
--- a/include/hw/arm/virt.h
+++ b/include/hw/arm/virt.h
@@ -144,6 +144,7 @@ struct VirtMachineState {
     PFlashCFI01 *flash[2];
     bool secure;
     bool highmem;
+    bool highmem_compact;
     bool highmem_ecam;
     bool highmem_mmio;
     bool highmem_redists;
-- 
2.31.1