Add status reporting for BGRT preservation and integrate with Xen's
ACPI subsystem:
- efi_bgrt_status_info() prints preservation status (success/failure)
- Called from acpi_boot_init() after ACPI tables are processed
- Clarifying comment explains why invalidation code remains

The invalidation code in acpi_invalidate_bgrt() now acts as a safety
net: if preservation fails, the image remains in conventional RAM
and gets invalidated. If preservation succeeds, the image is in
EfiACPIReclaimMemory which won't match the RAM_TYPE_CONVENTIONAL
check, leaving the table valid.

Signed-off-by: Soumyajyotii Ssarkar <soumyajyotisarkar23@gmail.com>
---
 xen/arch/x86/acpi/boot.c |  8 ++++++++
 xen/common/efi/boot.c    | 16 ++++++++++++++++
 xen/include/xen/efi.h    |  1 +
 3 files changed, 25 insertions(+)

diff --git a/xen/arch/x86/acpi/boot.c b/xen/arch/x86/acpi/boot.c
index 1ca2360e00..20afe79db9 100644
--- a/xen/arch/x86/acpi/boot.c
+++ b/xen/arch/x86/acpi/boot.c
@@ -29,6 +29,7 @@
 #include <xen/mm.h>
 #include <xen/param.h>
 #include <xen/dmi.h>
+#include <xen/efi.h>
 #include <asm/fixmap.h>
 #include <asm/page.h>
 #include <asm/apic.h>
@@ -327,6 +328,11 @@ static int __init cf_check acpi_parse_hpet(struct acpi_table_header *table)
 	return 0;
 }

+/*
+ * Invalidate BGRT if image is in conventional RAM (preservation failed).
+ * If preservation succeeded, image is in EfiACPIReclaimMemory, which
+ * won't match RAM_TYPE_CONVENTIONAL check, so table remains valid.
+ */
 static int __init cf_check acpi_invalidate_bgrt(struct acpi_table_header *table)
 {
 	struct acpi_table_bgrt *bgrt_tbl =
@@ -754,5 +760,7 @@ int __init acpi_boot_init(void)

 	acpi_table_parse(ACPI_SIG_BGRT, acpi_invalidate_bgrt);

+	efi_bgrt_status_info();
+
 	return 0;
 }
diff --git a/xen/common/efi/boot.c b/xen/common/efi/boot.c
index e6451130ce..68e06d707c 100644
--- a/xen/common/efi/boot.c
+++ b/xen/common/efi/boot.c
@@ -1911,6 +1911,22 @@ static bool __init cf_check rt_range_valid(unsigned long smfn, unsigned long emf
     return true;
 }

+void __init efi_bgrt_status_info(void)
+{
+    if ( !efi_enabled(EFI_BOOT) )
+        return;
+
+    if ( bgrt_info.preserved )
+    {
+        printk(XENLOG_INFO "EFI: BGRT image preserved: %lu KB\n",
+               bgrt_info.size / 1024);
+        printk(XENLOG_INFO "EFI: BGRT relocated from %p to %p\n",
+               bgrt_info.old_addr, bgrt_info.new_addr);
+    }
+    else if ( bgrt_info.failure_reason[0] )
+        printk(XENLOG_WARNING "EFI: BGRT preservation failed: %s\n",
+               bgrt_info.failure_reason);
+}

 void __init efi_init_memory(void)
 {
diff --git a/xen/include/xen/efi.h b/xen/include/xen/efi.h
index 723cb80852..e72ab3c6b5 100644
--- a/xen/include/xen/efi.h
+++ b/xen/include/xen/efi.h
@@ -39,6 +39,7 @@ static inline bool efi_enabled(unsigned int feature)
 extern bool efi_secure_boot;

 void efi_init_memory(void);
+void efi_bgrt_status_info(void);
 bool efi_boot_mem_unused(unsigned long *start, unsigned long *end);
 bool efi_rs_using_pgtables(void);
 unsigned long efi_get_time(void);
--
2.53.0

On 12/03/2026 11:14 am, Soumyajyotii Ssarkar wrote:
> diff --git a/xen/arch/x86/acpi/boot.c b/xen/arch/x86/acpi/boot.c
> index 1ca2360e00..20afe79db9 100644
> --- a/xen/arch/x86/acpi/boot.c
> +++ b/xen/arch/x86/acpi/boot.c
>  static int __init cf_check acpi_invalidate_bgrt(struct acpi_table_header *table)
>  {
>  	struct acpi_table_bgrt *bgrt_tbl =
> @@ -754,5 +760,7 @@ int __init acpi_boot_init(void)
>
>  	acpi_table_parse(ACPI_SIG_BGRT, acpi_invalidate_bgrt);
>
> +	efi_bgrt_status_info();

To help with your build failure, given this call from outside EFI code,
you need...

> +
>  	return 0;
>  }
> diff --git a/xen/common/efi/boot.c b/xen/common/efi/boot.c
> index e6451130ce..68e06d707c 100644
> --- a/xen/common/efi/boot.c
> +++ b/xen/common/efi/boot.c
> @@ -1911,6 +1911,22 @@ static bool __init cf_check rt_range_valid(unsigned long smfn, unsigned long emf
>      return true;
>  }
>
> +void __init efi_bgrt_status_info(void)
> +{
> +    if ( !efi_enabled(EFI_BOOT) )
> +        return;
> +
> +    if ( bgrt_info.preserved )
> +    {
> +        printk(XENLOG_INFO "EFI: BGRT image preserved: %lu KB\n",
> +               bgrt_info.size / 1024);
> +        printk(XENLOG_INFO "EFI: BGRT relocated from %p to %p\n",
> +               bgrt_info.old_addr, bgrt_info.new_addr);
> +    }
> +    else if ( bgrt_info.failure_reason[0] )
> +        printk(XENLOG_WARNING "EFI: BGRT preservation failed: %s\n",
> +               bgrt_info.failure_reason);
> +}

... a matching stub function in xen/common/efi/common-stub.c

xen.efi is constructed by taking non-efi Xen and linking in a few more
object files.  It is not a full rebuild with different toolchain settings.

~Andrew