diff mbox series

[PATCHv5,07/12] x86/mm: Reserve unaccepted memory bitmap

Message ID 20220425033934.68551-8-kirill.shutemov@linux.intel.com (mailing list archive)
State New
Headers show
Series mm, x86/cc: Implement support for unaccepted memory | expand

Commit Message

kirill.shutemov@linux.intel.com April 25, 2022, 3:39 a.m. UTC 
A given page of memory can only be accepted once. The kernel has a need
to accept memory both in the early decompression stage and during normal
runtime.

A bitmap used to communicate the acceptance state of each page between the
decompression stage and normal runtime.

boot_params is used to communicate location of the bitmap through out
the boot. The bitmap is allocated and initially populated in EFI stub.
Decompression stage accepts pages required for kernel/initrd and mark
these pages accordingly in the bitmap. The main kernel picks up the
bitmap from the same boot_params and uses it to determinate what has to
be accepted on allocation.

In the runtime kernel, reserve the bitmap's memory to ensure nothing
overwrites it.

The size of bitmap is determinated with e820__end_of_ram_pfn() which
relies on setup_e820() marking unaccepted memory as E820_TYPE_RAM.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
---
 arch/x86/kernel/e820.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

Comments

Wander Lairson Costa April 29, 2022, 1:19 p.m. UTC | #1 
On Mon, Apr 25, 2022 at 06:39:29AM +0300, Kirill A. Shutemov wrote:
> A given page of memory can only be accepted once. The kernel has a need
> to accept memory both in the early decompression stage and during normal
> runtime.
> 
> A bitmap used to communicate the acceptance state of each page between the

nit: s/bitmap used/bitmap is used/

[snip]
Borislav Petkov May 4, 2022, 11:04 a.m. UTC | #2 
On Mon, Apr 25, 2022 at 06:39:29AM +0300, Kirill A. Shutemov wrote:
> A given page of memory can only be accepted once. The kernel has a need

s/has a need to/has to/

> to accept memory both in the early decompression stage and during normal
> runtime.
> 
> A bitmap used to communicate the acceptance state of each page between the
	  ^
	  is

> decompression stage and normal runtime.
> 
> boot_params is used to communicate location of the bitmap through out

throughout

> the boot. The bitmap is allocated and initially populated in EFI stub.
> Decompression stage accepts pages required for kernel/initrd and mark

marks

> these pages accordingly in the bitmap. The main kernel picks up the
> bitmap from the same boot_params and uses it to determinate what has to

determine

> be accepted on allocation.
> 
> In the runtime kernel, reserve the bitmap's memory to ensure nothing
> overwrites it.
> 
> The size of bitmap is determinated with e820__end_of_ram_pfn() which

Unknown word [determinated] in commit message.
Suggestions: ['determinate', 'determined', 'terminated', 'determinant']
diff mbox series

Patch

diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index f267205f2d5a..22d1fe48dcba 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -1316,6 +1316,16 @@  void __init e820__memblock_setup(void)
 	int i;
 	u64 end;
 
+	/* Mark unaccepted memory bitmap reserved */
+	if (boot_params.unaccepted_memory) {
+		unsigned long size;
+
+		/* One bit per 2MB */
+		size = DIV_ROUND_UP(e820__end_of_ram_pfn() * PAGE_SIZE,
+				    PMD_SIZE * BITS_PER_BYTE);
+		memblock_reserve(boot_params.unaccepted_memory, size);
+	}
+
 	/*
 	 * The bootstrap memblock region count maximum is 128 entries
 	 * (INIT_MEMBLOCK_REGIONS), but EFI might pass us more E820 entries