From: "Gerd Hoffmann" <kraxel@redhat.com>
To: devel@edk2.groups.io
Cc: oliver@redhat.com, Gerd Hoffmann <kraxel@redhat.com>
Subject: [edk2-devel] [PATCH v2 2/6] OvmfPkg/VirtNorFlashDxe: clarify block write logic & fix shadowbuffer reads
Date: Mon, 15 Jan 2024 16:59:44 +0100 [thread overview]
Message-ID: <20240115155948.136499-3-kraxel@redhat.com> (raw)
In-Reply-To: <20240115155948.136499-1-kraxel@redhat.com>
Introduce 'Start' and 'End' variables to make it easier to follow the
logic and code flow. Also add a ascii art diagram (based on a
suggestion by Laszlo).
This also fixes the 'Size' calculation for the NorFlashRead() call.
Without this patch the code will read only one instead of two
P30_MAX_BUFFER_SIZE_IN_BYTES blocks in case '*NumBytes' is smaller than
P30_MAX_BUFFER_SIZE_IN_BYTES but 'Offset + *NumBytes' is not, i.e. the
update range crosses a P30_MAX_BUFFER_SIZE_IN_BYTES boundary.
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
OvmfPkg/VirtNorFlashDxe/VirtNorFlash.c | 35 ++++++++++++++++++++------
1 file changed, 27 insertions(+), 8 deletions(-)
diff --git a/OvmfPkg/VirtNorFlashDxe/VirtNorFlash.c b/OvmfPkg/VirtNorFlashDxe/VirtNorFlash.c
index 7f4743b00399..54251633d0ee 100644
--- a/OvmfPkg/VirtNorFlashDxe/VirtNorFlash.c
+++ b/OvmfPkg/VirtNorFlashDxe/VirtNorFlash.c
@@ -520,6 +520,7 @@ NorFlashWriteSingleBlock (
UINTN BlockSize;
UINTN BlockAddress;
UINT8 *OrigData;
+ UINTN Start, End;
DEBUG ((DEBUG_BLKIO, "NorFlashWriteSingleBlock(Parameters: Lba=%ld, Offset=0x%x, *NumBytes=0x%x, Buffer @ 0x%08x)\n", Lba, Offset, *NumBytes, Buffer));
@@ -555,7 +556,27 @@ NorFlashWriteSingleBlock (
// To avoid pathological cases were a 2 byte write is disregarded because it
// occurs right at a 128 byte buffered write alignment boundary, permit up to
// twice the max buffer size, and perform two writes if needed.
- if ((*NumBytes + (Offset & BOUNDARY_OF_32_WORDS)) <= (2 * P30_MAX_BUFFER_SIZE_IN_BYTES)) {
+ //
+ // 0 128 256
+ // [----------------|----------------]
+ // ^ ^ ^ ^
+ // | | | |
+ // | | | End, the next "word" boundary beyond
+ // | | | the (logical) update
+ // | | |
+ // | | (Offset & 0x7F) + NumBytes; i.e., the Offset inside
+ // | | (or just past) the *double-word* such that Offset is
+ // | | the *exclusive* end of the (logical) update.
+ // | |
+ // | Offset & BOUNDARY_OF_32_WORDS; i.e., Offset within the "word";
+ // | this is where the (logical) update is supposed to start
+ // |
+ // Start = Offset & ~BOUNDARY_OF_32_WORDS; i.e., Offset truncated to "word" boundary
+
+ Start = Offset & ~BOUNDARY_OF_32_WORDS;
+ End = ALIGN_VALUE (Offset + *NumBytes, P30_MAX_BUFFER_SIZE_IN_BYTES);
+
+ if ((End - Start) <= (2 * P30_MAX_BUFFER_SIZE_IN_BYTES)) {
// Check to see if we need to erase before programming the data into NOR.
// If the destination bits are only changing from 1s to 0s we can just write.
// After a block is erased all bits in the block is set to 1.
@@ -565,8 +586,8 @@ NorFlashWriteSingleBlock (
Status = NorFlashRead (
Instance,
Lba,
- Offset & ~BOUNDARY_OF_32_WORDS,
- (*NumBytes | BOUNDARY_OF_32_WORDS) + 1,
+ Start,
+ End - Start,
Instance->ShadowBuffer
);
if (EFI_ERROR (Status)) {
@@ -601,7 +622,7 @@ NorFlashWriteSingleBlock (
Status = NorFlashWriteBuffer (
Instance,
- BlockAddress + (Offset & ~BOUNDARY_OF_32_WORDS),
+ BlockAddress + Start,
P30_MAX_BUFFER_SIZE_IN_BYTES,
Instance->ShadowBuffer
);
@@ -609,12 +630,10 @@ NorFlashWriteSingleBlock (
goto Exit;
}
- if ((*NumBytes + (Offset & BOUNDARY_OF_32_WORDS)) > P30_MAX_BUFFER_SIZE_IN_BYTES) {
- BlockAddress += P30_MAX_BUFFER_SIZE_IN_BYTES;
-
+ if ((End - Start) > P30_MAX_BUFFER_SIZE_IN_BYTES) {
Status = NorFlashWriteBuffer (
Instance,
- BlockAddress + (Offset & ~BOUNDARY_OF_32_WORDS),
+ BlockAddress + Start + P30_MAX_BUFFER_SIZE_IN_BYTES,
P30_MAX_BUFFER_SIZE_IN_BYTES,
Instance->ShadowBuffer + P30_MAX_BUFFER_SIZE_IN_BYTES
);
--
2.43.0
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next prev parent reply other threads:[~2024-01-16 5:26 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-15 15:59 [edk2-devel] [PATCH v2 0/6] OvmfPkg/VirtNorFlashDxe: fix corruption + misc small improvements Gerd Hoffmann
2024-01-15 15:59 ` [edk2-devel] [PATCH v2 1/6] OvmfPkg/VirtNorFlashDxe: add casts to UINTN and UINT32 Gerd Hoffmann
2024-01-15 19:20 ` Laszlo Ersek
2024-01-15 15:59 ` Gerd Hoffmann [this message]
2024-01-16 12:48 ` [edk2-devel] [PATCH v2 2/6] OvmfPkg/VirtNorFlashDxe: clarify block write logic & fix shadowbuffer reads Laszlo Ersek
2024-01-15 15:59 ` [edk2-devel] [PATCH v2 3/6] OvmfPkg/VirtNorFlashDxe: add a loop for NorFlashWriteBuffer calls Gerd Hoffmann
2024-01-16 12:56 ` Laszlo Ersek
2024-01-15 15:59 ` [edk2-devel] [PATCH v2 4/6] OvmfPkg/VirtNorFlashDxe: allow larger writes without block erase Gerd Hoffmann
2024-01-16 12:59 ` Laszlo Ersek
2024-01-15 15:59 ` [edk2-devel] [PATCH v2 5/6] OvmfPkg/VirtNorFlashDxe: ValidateFvHeader: unwritten state is EOL too Gerd Hoffmann
2024-01-16 13:01 ` Laszlo Ersek
2024-01-15 15:59 ` [edk2-devel] [PATCH v2 6/6] OvmfPkg/VirtNorFlashDxe: move DoErase code block into new function Gerd Hoffmann
2024-01-16 13:44 ` Laszlo Ersek
2024-01-16 15:29 ` Laszlo Ersek
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