[PATCH v3 1/2] disk: read up to 63 sectors in LBA mode - ValdikSS via Grub-devel

From: ValdikSS via Grub-devel <grub-devel@gnu.org>
To: grub-devel@gnu.org
Cc: ValdikSS <iam@valdikss.org.ru>
Subject: [PATCH v3 1/2] disk: read up to 63 sectors in LBA mode
Date: Tue, 10 Oct 2023 21:28:44 +0300	[thread overview]
Message-ID: <20231010182906.18846-2-iam@valdikss.org.ru> (raw)
In-Reply-To: <20231010182906.18846-1-iam@valdikss.org.ru>

Current code impose limitations on the amount of sectors read
in a single call according to CHS layout of the disk, even in LBA
read mode.

There's no need to obey CHS layout restrictions for LBA reads
on LBA disks, it only slows down booting process.

See: https://lore.kernel.org/grub-devel/d42a11fa-2a59-b5e7-08b1-d2c60444bb99@valdikss.org.ru/

Signed-off-by: ValdikSS <iam@valdikss.org.ru>
---
 grub-core/disk/i386/pc/biosdisk.c | 5 ++++-
 include/grub/disk.h               | 3 +++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/grub-core/disk/i386/pc/biosdisk.c b/grub-core/disk/i386/pc/biosdisk.c
index f9362d17c..1d6788950 100644
--- a/grub-core/disk/i386/pc/biosdisk.c
+++ b/grub-core/disk/i386/pc/biosdisk.c
@@ -471,7 +471,7 @@ grub_biosdisk_rw (int cmd, grub_disk_t disk,
       struct grub_biosdisk_dap *dap;
 
       dap = (struct grub_biosdisk_dap *) (GRUB_MEMORY_MACHINE_SCRATCH_ADDR
-					  + (data->sectors
+					  + (GRUB_DISK_MAX_LBA_SECTORS
 					     << disk->log_sector_size));
       dap->length = sizeof (*dap);
       dap->reserved = 0;
@@ -561,6 +561,9 @@ get_safe_sectors (grub_disk_t disk, grub_disk_addr_t sector)
   struct grub_biosdisk_data *data = disk->data;
   grub_uint32_t sectors = data->sectors;
 
+  if (data->flags & GRUB_BIOSDISK_FLAG_LBA)
+    sectors = GRUB_DISK_MAX_LBA_SECTORS;
+
   /* OFFSET = SECTOR % SECTORS */
   grub_divmod64 (sector, sectors, &offset);
 
diff --git a/include/grub/disk.h b/include/grub/disk.h
index a4b5d13f3..be032a72c 100644
--- a/include/grub/disk.h
+++ b/include/grub/disk.h
@@ -190,6 +190,9 @@ typedef struct grub_disk_memberlist *grub_disk_memberlist_t;
 
 #define GRUB_DISK_MAX_MAX_AGGLOMERATE ((1 << (30 - GRUB_DISK_CACHE_BITS - GRUB_DISK_SECTOR_BITS)) - 1)
 
+/* Maximum number of sectors to read in LBA mode at once */
+#define GRUB_DISK_MAX_LBA_SECTORS 63
+
 /* Return value of grub_disk_native_sectors() in case disk size is unknown. */
 #define GRUB_DISK_SIZE_UNKNOWN	 0xffffffffffffffffULL
 
-- 
2.41.0


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