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Re: [PATCH v4] EFI: always map EfiRuntimeServices{Code,Data}



Hi Jan,

On 12/01/2022 08:45, Jan Beulich wrote:
From: Sergey Temerkhanov <s.temerkhanov@xxxxxxxxx>

This helps overcome problems observed with some UEFI implementations

Would it be possible to provide some details about the platform? This is helpful to track why a workaround is present.

which don't set the Attributes field in memery descriptors properly.

typo: s/memery/memory/


Signed-off-by: Sergey Temerkhanov <s.temerkhanov@xxxxxxxxx>
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
v4: Drop EFI_MEMORY_CACHEABILITY_MASK. Fold with pre-existing if() (into
     switch()). Style.
---
I guess "map_bs" would also want honoring in efi_exit_boot(), but that's
yet another patch then I suppose.

IIUC, we would need to invalidate the mapping when map_bs was used. Is it correct? If so, then I agree this sounds separate to the issue you are describing here.


--- a/xen/common/efi/boot.c
+++ b/xen/common/efi/boot.c
@@ -1094,7 +1094,13 @@ static void __init efi_exit_boot(EFI_HAN
      {
          EFI_MEMORY_DESCRIPTOR *desc = efi_memmap + i;
- if ( desc->Attribute & EFI_MEMORY_RUNTIME )
+        /*
+         * Runtime services regions are always mapped here.
+         * Attributes may be adjusted in efi_init_memory().
+         */
+        if ( (desc->Attribute & EFI_MEMORY_RUNTIME) ||
+             desc->Type == EfiRuntimeServicesCode ||
+             desc->Type == EfiRuntimeServicesData )

My knowledge with the stub is limited. Would you be able to explain why we need to map the runtime services even with !efi_enabled(EFI_RS)?

The reason I am asking is if we don't need it, then it would be sufficient to rely on desc->Attribute because you updated it in efi_init_memory().

              desc->VirtualStart = desc->PhysicalStart;
          else
              desc->VirtualStart = INVALID_VIRTUAL_ADDRESS;
@@ -1545,13 +1551,36 @@ void __init efi_init_memory(void)
                      ROUNDUP(desc->PhysicalStart + len, PAGE_SIZE));
          }
- if ( !efi_enabled(EFI_RS) ||
-             (!(desc->Attribute & EFI_MEMORY_RUNTIME) &&
-              (!map_bs ||
-               (desc->Type != EfiBootServicesCode &&
-                desc->Type != EfiBootServicesData))) )
+        if ( !efi_enabled(EFI_RS) )
              continue;
+ if ( !(desc->Attribute & EFI_MEMORY_RUNTIME) )
+        {
+            switch ( desc->Type )
+            {
+            default:
+                continue;
+
+            /*
+             * Adjust runtime services regions. Keep in sync with
+             * efi_exit_boot().
+             */
+            case EfiRuntimeServicesCode:
+            case EfiRuntimeServicesData:
+                printk(XENLOG_WARNING
+                       "Setting RUNTIME attribute for %013" PRIx64 "-%013" PRIx64 
"\n",
+                       desc->PhysicalStart, desc->PhysicalStart + len - 1);
+                desc->Attribute |= EFI_MEMORY_RUNTIME;
+                break;
+
+            case EfiBootServicesCode:
+            case EfiBootServicesData:
+                if ( !map_bs )
+                    continue;
+                break;
+            }
+        }

The new code is much easier to read :).


+
          desc->VirtualStart = INVALID_VIRTUAL_ADDRESS;
smfn = PFN_DOWN(desc->PhysicalStart);


Cheers,

--
Julien Grall



 


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