From: "Roger Pau Monné" <roger.pau@citrix.com>
To: Elias El Yandouzi <eliasely@amazon.com>
Cc: xen-devel@lists.xenproject.org, julien@xen.org,
pdurrant@amazon.com, dwmw@amazon.com,
Hongyan Xia <hongyxia@amazon.com>,
Jan Beulich <jbeulich@suse.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Julien Grall <jgrall@amazon.com>
Subject: Re: [PATCH V3 (resend) 11/19] x86/setup: Leave early boot slightly earlier
Date: Tue, 14 May 2024 16:11:07 +0200 [thread overview]
Message-ID: <ZkNw--0ilcMh5YeB@macbook> (raw)
In-Reply-To: <20240513134046.82605-12-eliasely@amazon.com>
On Mon, May 13, 2024 at 01:40:38PM +0000, Elias El Yandouzi wrote:
> From: Hongyan Xia <hongyxia@amazon.com>
>
> When we do not have a direct map, memory for metadata of heap nodes in
> init_node_heap() is allocated from xenheap, which needs to be mapped and
> unmapped on demand. However, we cannot just take memory from the boot
> allocator to create the PTEs while we are passing memory to the heap
> allocator.
>
> To solve this race, we leave early boot slightly sooner so that Xen PTE
> pages are allocated from the heap instead of the boot allocator. We can
> do this because the metadata for the 1st node is statically allocated,
> and by the time we need memory to create mappings for the 2nd node, we
> already have enough memory in the heap allocator in the 1st node.
>
> Signed-off-by: Hongyan Xia <hongyxia@amazon.com>
> Signed-off-by: Julien Grall <jgrall@amazon.com>
> Signed-off-by: Elias El Yandouzi <eliasely@amazon.com>
>
> diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
> index bd6b1184f5..f26c9799e4 100644
> --- a/xen/arch/x86/setup.c
> +++ b/xen/arch/x86/setup.c
> @@ -1751,6 +1751,22 @@ void asmlinkage __init noreturn __start_xen(unsigned long mbi_p)
>
> numa_initmem_init(0, raw_max_page);
>
> + /*
> + * When we do not have a direct map, memory for metadata of heap nodes in
> + * init_node_heap() is allocated from xenheap, which needs to be mapped and
> + * unmapped on demand.
Hm, maybe I'm confused, but isn't xenheap memory supposed to be always
mapped when in use? In one of the previous patches xenheap memory is
unconditionally mapped in alloc_xenheap_pages().
IMO, this would better be worded as: "... is allocated from xenheap,
which needs to be mapped at allocation and unmapped when freed."
> However, we cannot just take memory from the boot
> + * allocator to create the PTEs while we are passing memory to the heap
> + * allocator during end_boot_allocator().
Could you elaborate here, I don't obviously see why we can't consume
memory from the boot allocator. Is it because under certain
conditions we might try to allocate memory from the boot allocator in
order to fulfill a call to map_pages_to_xen() and find the boot
allocator empty?
Thanks, Roger.
next prev parent reply other threads:[~2024-05-14 14:11 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-13 13:40 [PATCH V3 (resend) 00/19] Remove the directmap Elias El Yandouzi
2024-05-13 13:40 ` [PATCH V3 (resend) 01/19] x86: Create per-domain mapping of guest_root_pt Elias El Yandouzi
2024-05-14 14:51 ` Jan Beulich
2024-05-15 18:25 ` Elias El Yandouzi
2024-05-16 7:17 ` Jan Beulich
2024-06-13 16:31 ` Elias El Yandouzi
2024-06-14 6:23 ` Jan Beulich
2024-06-17 7:33 ` Roger Pau Monné
2024-05-13 13:40 ` [PATCH V3 (resend) 02/19] x86/pv: Domheap pages should be mapped while relocating initrd Elias El Yandouzi
2024-05-13 15:40 ` Roger Pau Monné
2024-05-13 13:40 ` [PATCH V3 (resend) 03/19] x86/pv: Rewrite how building PV dom0 handles domheap mappings Elias El Yandouzi
2024-05-13 16:49 ` Roger Pau Monné
2024-05-14 14:58 ` Jan Beulich
2024-05-14 15:03 ` Jan Beulich
2024-05-13 13:40 ` [PATCH V3 (resend) 04/19] x86: Lift mapcache variable to the arch level Elias El Yandouzi
2024-05-14 8:21 ` Roger Pau Monné
2024-05-15 13:11 ` Jan Beulich
2024-05-13 13:40 ` [PATCH V3 (resend) 05/19] x86/mapcache: Initialise the mapcache for the idle domain Elias El Yandouzi
2024-05-14 8:42 ` Roger Pau Monné
2024-05-15 13:44 ` Jan Beulich
2024-05-13 13:40 ` [PATCH V3 (resend) 06/19] x86: Add a boot option to enable and disable the direct map Elias El Yandouzi
2024-05-14 9:20 ` Roger Pau Monné
2024-05-14 10:20 ` Roger Pau Monné
2024-05-15 13:54 ` Jan Beulich
2024-05-16 9:19 ` Roger Pau Monné
2024-05-16 9:24 ` Jan Beulich
2024-05-15 13:59 ` Jan Beulich
2024-05-15 16:02 ` Jan Beulich
2024-05-13 13:40 ` [PATCH V3 (resend) 07/19] xen/x86: Add support for the PMAP Elias El Yandouzi
2024-05-14 9:40 ` Roger Pau Monné
2024-05-14 9:43 ` Jan Beulich
2024-05-14 10:22 ` Roger Pau Monné
2024-05-14 10:26 ` Jan Beulich
2024-05-14 11:51 ` Roger Pau Monné
2024-05-14 12:33 ` Jan Beulich
2024-05-13 13:40 ` [PATCH V3 (resend) 08/19] xen/x86: Add build assertion for fixmap entries Elias El Yandouzi
2024-05-14 9:42 ` Roger Pau Monné
2024-05-14 9:45 ` Jan Beulich
2024-05-15 14:03 ` Jan Beulich
2024-05-13 13:40 ` [PATCH V3 (resend) 09/19] x86/domain_page: Remove the fast paths when mfn is not in the directmap Elias El Yandouzi
2024-05-14 11:48 ` Roger Pau Monné
2024-05-15 14:21 ` Jan Beulich
2024-05-13 13:40 ` [PATCH V3 (resend) 10/19] xen/page_alloc: Add a path for xenheap when there is no direct map Elias El Yandouzi
2024-05-14 13:07 ` Roger Pau Monné
2024-05-15 15:13 ` Jan Beulich
2024-05-13 13:40 ` [PATCH V3 (resend) 11/19] x86/setup: Leave early boot slightly earlier Elias El Yandouzi
2024-05-14 14:11 ` Roger Pau Monné [this message]
2024-05-15 15:22 ` Jan Beulich
2024-05-13 13:40 ` [PATCH V3 (resend) 12/19] x86/setup: vmap heap nodes when they are outside the direct map Elias El Yandouzi
2024-05-14 15:02 ` Roger Pau Monné
2024-05-15 15:28 ` Jan Beulich
2024-05-13 13:40 ` [PATCH V3 (resend) 13/19] x86/setup: Do not create valid mappings when directmap=no Elias El Yandouzi
2024-05-14 15:39 ` Roger Pau Monné
2024-05-15 15:50 ` Jan Beulich
2024-05-15 15:59 ` Jan Beulich
2024-05-13 13:40 ` [PATCH V3 (resend) 14/19] Rename mfn_to_virt() calls Elias El Yandouzi
2024-05-14 15:45 ` Roger Pau Monné
2024-05-14 16:22 ` Jan Beulich
2024-05-15 9:38 ` Roger Pau Monné
2024-05-15 9:42 ` Jan Beulich
2024-05-16 8:57 ` Jan Beulich
2024-05-13 13:40 ` [PATCH V3 (resend) 15/19] Rename maddr_to_virt() calls Elias El Yandouzi
2024-05-13 13:40 ` [PATCH V3 (resend) 16/19] xen/arm32: mm: Rename 'first' to 'root' in init_secondary_pagetables() Elias El Yandouzi
2024-05-13 13:40 ` [PATCH V3 (resend) 17/19] xen/arm64: mm: Use per-pCPU page-tables Elias El Yandouzi
2024-05-13 13:40 ` [PATCH V3 (resend) 18/19] xen/arm64: Implement a mapcache for arm64 Elias El Yandouzi
2024-05-13 13:40 ` [PATCH V3 (resend) 19/19] xen/arm64: Allow the admin to enable/disable the directmap Elias El Yandouzi
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