ACPI: PRM: Reduce unnecessary printing to avoid user confusion

Commit 088984c8d54c ("ACPI: PRM: Find EFI_MEMORY_RUNTIME block for PRM
handler and context") introduced non-essential printing "Failed to find
VA for GUID: xxxx, PA: 0x0" which may confuse users to think that
something wrong is going on while it is not the case.

According to the PRM Spec Section 4.1.2 [1], both static data buffer
address and ACPI parameter buffer address may be NULL if they are not
needed, so there is no need to print out the "Failed to find VA ... "
in those cases.

Link: https://uefi.org/sites/default/files/resources/Platform%20Runtime%20Mechanism%20-%20with%20legal%20notice.pdf
Signed-off-by: Zhu Qiyu <qiyuzhu2@amd.com>
Link: https://patch.msgid.link/20250704014104.82524-1-qiyuzhu2@amd.com
[ rjw: Edits in new comments, subject and changelog ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/acpi/prmt.c b/drivers/acpi/prmt.c
index e549914a636c66c505d49dc6a93fed2b91859646..be033bbb126a444c196c2ad2e3f6db9a99a7abb1 100644 (file)
--- a/drivers/acpi/prmt.c
+++ b/drivers/acpi/prmt.c
@@ -85,8 +85,6 @@ static u64 efi_pa_va_lookup(efi_guid_t *guid, u64 pa)
                }
        }
 
-       pr_warn("Failed to find VA for GUID: %pUL, PA: 0x%llx", guid, pa);
-
        return 0;
 }
 
@@ -154,13 +152,37 @@ acpi_parse_prmt(union acpi_subtable_headers *header, const unsigned long end)
                guid_copy(&th->guid, (guid_t *)handler_info->handler_guid);
                th->handler_addr =
                        (void *)efi_pa_va_lookup(&th->guid, handler_info->handler_address);
+               /*
+                * Print a warning message if handler_addr is zero which is not expected to
+                * ever happen.
+                */
+               if (unlikely(!th->handler_addr))
+                       pr_warn("Failed to find VA of handler for GUID: %pUL, PA: 0x%llx",
+                               &th->guid, handler_info->handler_address);
 
                th->static_data_buffer_addr =
                        efi_pa_va_lookup(&th->guid, handler_info->static_data_buffer_address);
+               /*
+                * According to the PRM specification, static_data_buffer_address can be zero,
+                * so avoid printing a warning message in that case.  Otherwise, if the
+                * return value of efi_pa_va_lookup() is zero, print the message.
+                */
+               if (unlikely(!th->static_data_buffer_addr && handler_info->static_data_buffer_address))
+                       pr_warn("Failed to find VA of static data buffer for GUID: %pUL, PA: 0x%llx",
+                               &th->guid, handler_info->static_data_buffer_address);
 
                th->acpi_param_buffer_addr =
                        efi_pa_va_lookup(&th->guid, handler_info->acpi_param_buffer_address);
 
+               /*
+                * According to the PRM specification, acpi_param_buffer_address can be zero,
+                * so avoid printing a warning message in that case.  Otherwise, if the
+                * return value of efi_pa_va_lookup() is zero, print the message.
+                */
+               if (unlikely(!th->acpi_param_buffer_addr && handler_info->acpi_param_buffer_address))
+                       pr_warn("Failed to find VA of acpi param buffer for GUID: %pUL, PA: 0x%llx",
+                               &th->guid, handler_info->acpi_param_buffer_address);
+
        } while (++cur_handler < tm->handler_count && (handler_info = get_next_handler(handler_info)));
 
        return 0;