edk2/edk2-OvmfPkg-VirtNorFlashDxe-avoid-array-mode-switch-afte.patch

From 20ba071dabad6b0f5663083a017799b7a6e684c5 Mon Sep 17 00:00:00 2001
From: Ard Biesheuvel <ardb@kernel.org>
Date: Mon, 24 Oct 2022 17:34:09 +0200
Subject: [PATCH 05/18] OvmfPkg/VirtNorFlashDxe: avoid array mode switch after
 each word write

RH-Author: Gerd Hoffmann <None>
RH-MergeRequest: 43: OvmfPkg/VirtNorFlashDxe backport
RH-Jira: RHEL-17587
RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
RH-Commit: [7/20] 274f2ed71a6d5d3f6497129ee3c62f494cc2f067

NorFlashWriteSingleWord() switches into programming mode and back into
array mode for every single word that it writes. Under KVM, this
involves tearing down the read-only memslot, and setting it up again,
which is costly and unnecessary.

Instead, move the array mode switch into the callers, and only make the
switch when the writing is done.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Sunil V L <sunilvl@ventanamicro.com>
(cherry picked from commit ca01e6216a8d1a26c69018e216d1dc3f88a819a4)
---
 OvmfPkg/VirtNorFlashDxe/VirtNorFlash.c    | 12 +++---------
 OvmfPkg/VirtNorFlashDxe/VirtNorFlashDxe.c |  3 +++
 2 files changed, 6 insertions(+), 9 deletions(-)

diff --git a/OvmfPkg/VirtNorFlashDxe/VirtNorFlash.c b/OvmfPkg/VirtNorFlashDxe/VirtNorFlash.c
index f41d9d372f..0a5c5d48c7 100644
--- a/OvmfPkg/VirtNorFlashDxe/VirtNorFlash.c
+++ b/OvmfPkg/VirtNorFlashDxe/VirtNorFlash.c
@@ -205,9 +205,6 @@ NorFlashWriteSingleWord (
     SEND_NOR_COMMAND (Instance->DeviceBaseAddress, 0, P30_CMD_CLEAR_STATUS_REGISTER);
   }
 
-  // Put device back into Read Array mode
-  SEND_NOR_COMMAND (Instance->DeviceBaseAddress, 0, P30_CMD_READ_ARRAY);
-
   return Status;
 }
 
@@ -286,8 +283,7 @@ NorFlashWriteBuffer (
 
   // The buffer was not available for writing
   if (WaitForBuffer == 0) {
-    Status = EFI_DEVICE_ERROR;
-    goto EXIT;
+    return EFI_DEVICE_ERROR;
   }
 
   // From now on we work in 32-bit words
@@ -337,10 +333,6 @@ NorFlashWriteBuffer (
     SEND_NOR_COMMAND (Instance->DeviceBaseAddress, 0, P30_CMD_CLEAR_STATUS_REGISTER);
   }
 
-EXIT:
-  // Put device back into Read Array mode
-  SEND_NOR_COMMAND (Instance->DeviceBaseAddress, 0, P30_CMD_READ_ARRAY);
-
   return Status;
 }
 
@@ -739,6 +731,8 @@ NorFlashWriteSingleBlock (
       }
 
       TempStatus = NorFlashWriteSingleWord (Instance, WordAddr, WordToWrite);
+      // Put device back into Read Array mode
+      SEND_NOR_COMMAND (Instance->DeviceBaseAddress, 0, P30_CMD_READ_ARRAY);
       if (EFI_ERROR (TempStatus)) {
         return EFI_DEVICE_ERROR;
       }
diff --git a/OvmfPkg/VirtNorFlashDxe/VirtNorFlashDxe.c b/OvmfPkg/VirtNorFlashDxe/VirtNorFlashDxe.c
index 2ceda22635..f9a41f6aab 100644
--- a/OvmfPkg/VirtNorFlashDxe/VirtNorFlashDxe.c
+++ b/OvmfPkg/VirtNorFlashDxe/VirtNorFlashDxe.c
@@ -280,6 +280,9 @@ NorFlashWriteFullBlock (
   }
 
 EXIT:
+  // Put device back into Read Array mode
+  SEND_NOR_COMMAND (Instance->DeviceBaseAddress, 0, P30_CMD_READ_ARRAY);
+
   if (!EfiAtRuntime ()) {
     // Interruptions can resume.
     gBS->RestoreTPL (OriginalTPL);
-- 
2.41.0