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Re: [PATCH v3 4/5] hw/arm/virt: Improve high memory region address assig
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From: |
Gavin Shan |
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Subject: |
Re: [PATCH v3 4/5] hw/arm/virt: Improve high memory region address assignment |
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Date: |
Tue, 4 Oct 2022 06:17:39 +0800 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.0 |
Hi Eric,
On 10/3/22 4:44 PM, Eric Auger wrote:
On 9/29/22 01:37, Gavin Shan wrote:
On 9/28/22 10:51 PM, Eric Auger wrote:
On 9/22/22 01:13, Gavin Shan wrote:
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 disabled by developer 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() isn't comprehensive
because the space for one specific high memory region is always
reserved from the PA space for case (1), (2) and (3). In the code,
'base' and 'vms->highest_gpa' are always increased for those three
cases. It's unnecessary since the assigned space of the disabled
high memory region won't be used afterwards.
This improves 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).
Signed-off-by: Gavin Shan <gshan@redhat.com>
---
hw/arm/virt.c | 44 ++++++++++++++++++++++++++------------------
1 file changed, 26 insertions(+), 18 deletions(-)
diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index b0b679d1f4..b702f8f2b5 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -1693,15 +1693,31 @@ static void
virt_set_high_memmap(VirtMachineState *vms,
hwaddr base, int pa_bits)
{
hwaddr region_base, region_size;
- bool fits;
+ bool *region_enabled, fits;
IDo you really need a pointer? If the region is unknown this is a bug in
virt code.
The pointer is needed so that we can disable the region by setting
'false'
to it at later point. Yeah, I think you're correct that 'unknown region'
is a bug and we need to do assert(region_enabled), or something like
below.
Yeah I don't think using a pointer here is useful.
When the high memory region can't fit into the PA space, it is disabled
by toggling the corresponding flag (vms->highmem_{redists, ecam, mmio})
to false. It's part of the original implementation, as below. We either
need a 'switch ... case' or a pointer. A pointer is more convenient since
we need check and possibly update to the value.
switch (i) {
case VIRT_HIGH_GIC_REDIST2:
vms->highmem_redists &= fits;
break;
case VIRT_HIGH_PCIE_ECAM:
vms->highmem_ecam &= fits;
break;
case VIRT_HIGH_PCIE_MMIO:
vms->highmem_mmio &= fits;
break;
}
int i;
for (i = VIRT_LOWMEMMAP_LAST; i <
ARRAY_SIZE(extended_memmap); i++) {
region_base = ROUND_UP(base, extended_memmap[i].size);
region_size = extended_memmap[i].size;
- vms->memmap[i].base = region_base;
- vms->memmap[i].size = region_size;
+ switch (i) {
+ case VIRT_HIGH_GIC_REDIST2:
+ region_enabled = &vms->highmem_redists;
+ break;
+ case VIRT_HIGH_PCIE_ECAM:
+ region_enabled = &vms->highmem_ecam;
+ break;
+ case VIRT_HIGH_PCIE_MMIO:
+ region_enabled = &vms->highmem_mmio;
+ break;
While we are at it I would change the vms fields dealing with those
highmem regions and turn those fields into an array of bool indexed
using i - VIRT_LOWMEMMAP_LAST (using a macro or something alike). We
would not be obliged to have this switch, now duplicated.
It makes sense to me. How about to have something like below in v4?
static inline bool *virt_get_high_memmap_enabled(VirtMachineState
*vms, int index)
{
bool *enabled_array[] = {
&vms->highmem_redists,
&vms->highmem_ecam,
&vms->highmem_mmio,
};
assert(index - VIRT_LOWMEMMAP_LAST < ARRAY_SIZE(enabled_array));
return enabled_array[index - VIRT_LOWMEMMAP_LAST];
}
I was rather thinking as directly using a vms->highmem_flags[] but your
proposal may work as well.
Ok. I will use my proposed change in next revision.
+ default:
+ region_enabled = NULL;
+ }
+
+ /* Skip unknown region */
+ if (!region_enabled) {
+ continue;
+ }
/*
* Check each device to see if they fit in the PA space,
@@ -1710,23 +1726,15 @@ static void
virt_set_high_memmap(VirtMachineState *vms,
* 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;
- }
+ if (*region_enabled && fits) {
+ vms->memmap[i].base = region_base;
+ vms->memmap[i].size = region_size;
- switch (i) {
- case VIRT_HIGH_GIC_REDIST2:
- vms->highmem_redists &= fits;
- break;
- case VIRT_HIGH_PCIE_ECAM:
- vms->highmem_ecam &= fits;
- break;
- case VIRT_HIGH_PCIE_MMIO:
- vms->highmem_mmio &= fits;
- break;
+ vms->highest_gpa = region_base + region_size - 1;
+ base = region_base + region_size;
+ } else {
+ *region_enabled = false;
what's the purpose to update the region_enabled here? Is it used anywhere?
The fact you do not update vms->highmem_* flags may introduce
regressions I think as the resulting flag may be used in some places
such as:
virt_gicv3_redist_region_count().
'region_enabled' points to 'vms->highmem_{redist2, ecam, mmio}'. They
are same thing.
-
- base = region_base + region_size;
}
}
Thanks,
Gavin