linux-kernel - [PATCH V6] ACPI:PRM: Reduce unnecessary printing to avoid the worries of regular users

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Message-ID: <20250704014104.82524-1-qiyuzhu2@amd.com>
Date: Fri, 4 Jul 2025 01:41:04 +0000
From: Zhu Qiyu <qiyuzhu2@....com>
To: <rafael@...nel.org>
CC: <lenb@...nel.org>, <linux-acpi@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <qiyuzhu2@....com>
Subject: [PATCH V6] ACPI:PRM: Reduce unnecessary printing to avoid the worries of regular users

Commit 088984c8d54c ("ACPI: PRM: Find EFI_MEMORY_RUNTIME block for PRM
handler and context") introduces non-essential printing "Failed to find
VA for GUID: xxxx, PA: 0x0" which causes unnecessary worry for regular
users.

Refer to 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 "Failed to find VA ... " to intimidate
regular users in that case.

Link: https://uefi.org/sites/default/files/resources/Platform%20Runtime%20Mechanism%20-%20with%20legal%20notice.pdf # [1]

Signed-off-by: Zhu Qiyu <qiyuzhu2@....com>
---
Previous versions can be found at:
v1: https://lore.kernel.org/linux-acpi/20250427075317.42687-1-qiyuzhu2@amd.com/
v2: https://lore.kernel.org/linux-acpi/20250512010620.142155-1-qiyuzhu2@amd.com/#r
v3: https://lore.kernel.org/linux-acpi/20250512011833.142204-1-qiyuzhu2@amd.com/t/#u
v4: https://lore.kernel.org/linux-acpi/20250518062507.218855-1-qiyuzhu2@amd.com/
v5: https://lore.kernel.org/all/20250527024259.56996-1-qiyuzhu2@amd.com/

Changes in v2:
 - Reduce the code changes.
Changes in v3:
 - Fixed title letters not showing.
Changes in v4:
 - Only print the necessary warnings.
Changes in v5:
 - Add more cases of print warnings.
Changes in v6:
-  Adjust the code comments.

 drivers/acpi/prmt.c | 28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/drivers/acpi/prmt.c b/drivers/acpi/prmt.c
index e549914a636c..d7857ca8fb4c 100644
--- 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 +152,39 @@ 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.
+		 * If the static_data_buffer_address passed to efi_pa_va_lookup() is nonzero
+		 * and the return value is zero, print a warning message in that case.
+		 */
+		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.
+		 * If the acpi_param_buffer_address passed to efi_pa_va_lookup() is nonzero and
+		 * the return value is zero, print a warning message in that case.
+		 */
+		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;

base-commit: a5806cd506af5a7c19bcd596e4708b5c464bfd21
-- 
2.43.0