[Xen-devel] [PATCH v2] xen/arm: during efi boot, improve the check for usable memory

[Stefano Stabellini <sstabellini@kernel.org>]

When booting via EFI, the EFI memory map has information about memory
regions and their type. Improve the check for the type and attribute of
each memory region to figure out whether it is usable memory or not.
This patch brings the check on par with Linux v5.5-rc6 and makes more
memory reusable as normal memory by Xen (except that Linux also reuses
EFI_PERSISTENT_MEMORY, which we do not).

Specifically, this patch also reuses memory marked as
EfiLoaderCode/Data, and it uses both Attribute and Type for the check
(Attribute needs to be EFI_MEMORY_WB).

Reported-by: Roman Shaposhnik <roman@zededa.com>
Signed-off-by: Stefano Stabellini <stefano.stabellini@xilinx.com>
CC: Julien Grall <julien@xen.org>

---
Changes in v2:
- improve commit message
- do not allocate memory marked as EFI_PERSISTENT_MEMORY
- do not change map_bs' behavior
---
 xen/arch/arm/efi/efi-boot.h | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/xen/arch/arm/efi/efi-boot.h b/xen/arch/arm/efi/efi-boot.h
index d7bf934077..6527cb0bdf 100644
--- a/xen/arch/arm/efi/efi-boot.h
+++ b/xen/arch/arm/efi/efi-boot.h
@@ -149,10 +149,13 @@ static EFI_STATUS __init efi_process_memory_map_bootinfo(EFI_MEMORY_DESCRIPTOR *
 
     for ( Index = 0; Index < (mmap_size / desc_size); Index++ )
     {
-        if ( desc_ptr->Type == EfiConventionalMemory ||
-             (!map_bs &&
-              (desc_ptr->Type == EfiBootServicesCode ||
-               desc_ptr->Type == EfiBootServicesData)) )
+        if ( desc_ptr->Attribute & EFI_MEMORY_WB &&
+             (desc_ptr->Type == EfiConventionalMemory ||
+              desc_ptr->Type == EfiLoaderCode ||
+              desc_ptr->Type == EfiLoaderData ||
+              (!map_bs &&
+               (desc_ptr->Type == EfiBootServicesCode ||
+                desc_ptr->Type == EfiBootServicesData))) )
         {
             if ( !meminfo_add_bank(&bootinfo.mem, desc_ptr) )
             {
-- 
2.17.1


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