From: Stefano Stabellini <sstabellini@kernel.org>
To: Julien Grall <julien@xen.org>
Cc: xen-devel@lists.xenproject.org, Wei.Chen@arm.com,
Henry.Wang@arm.com, Penny.Zheng@arm.com,
Bertrand.Marquis@arm.com, Julien Grall <julien.grall@arm.com>,
Stefano Stabellini <sstabellini@kernel.org>,
Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>,
Julien Grall <jgrall@amazon.com>
Subject: Re: [PATCH RFCv2 04/15] xen/arm: mm: Allow other mapping size in xen_pt_update_entry()
Date: Tue, 11 May 2021 15:42:40 -0700 (PDT) [thread overview]
Message-ID: <alpine.DEB.2.21.2105111542290.5018@sstabellini-ThinkPad-T480s> (raw)
In-Reply-To: <20210425201318.15447-5-julien@xen.org>
On Sun, 25 Apr 2021, Julien Grall wrote:
> From: Julien Grall <julien.grall@arm.com>
>
> At the moment, xen_pt_update_entry() only supports mapping at level 3
> (i.e 4KB mapping). While this is fine for most of the runtime helper,
> the boot code will require to use superpage mapping.
>
> We don't want to allow superpage mapping by default as some of the
> callers may expect small mappings (i.e populate_pt_range()) or even
> expect to unmap only a part of a superpage.
>
> To keep the code simple, a new flag _PAGE_BLOCK is introduced to
> allow the caller to enable superpage mapping.
>
> As the code doesn't support all the combinations, xen_pt_check_entry()
> is extended to take into account the cases we don't support when
> using block mapping:
> - Replacing a table with a mapping. This may happen if region was
> first mapped with 4KB mapping and then later on replaced with a 2MB
> (or 1GB mapping)
> - Removing/modify a table. This may happen if a caller try to
> remove a region with _PAGE_BLOCK set when it was created without it
>
> Note that the current restriction mean that the caller must ensure that
> _PAGE_BLOCK is consistently set/cleared across all the updates on a
> given virtual region. This ought to be fine with the expected use-cases.
>
> More rework will be necessary if we wanted to remove the restrictions.
>
> Note that nr_mfns is now marked const as it is used for flushing the
> TLBs and we don't want it to be modified.
>
> Signed-off-by: Julien Grall <julien.grall@arm.com>
> Signed-off-by: Julien Grall <jgrall@amazon.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
> ---
>
> Changes in v2:
> - Pass the target level rather than the order to
> xen_pt_update_entry()
> - Update some comments
> - Open-code paddr_to_pfn()
> - Add my AWS signed-off-by
> ---
> xen/arch/arm/mm.c | 93 ++++++++++++++++++++++++++++++--------
> xen/include/asm-arm/page.h | 4 ++
> 2 files changed, 79 insertions(+), 18 deletions(-)
>
> diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
> index 59f8a3f15fd1..8ebb36899314 100644
> --- a/xen/arch/arm/mm.c
> +++ b/xen/arch/arm/mm.c
> @@ -1060,9 +1060,10 @@ static int xen_pt_next_level(bool read_only, unsigned int level,
> }
>
> /* Sanity check of the entry */
> -static bool xen_pt_check_entry(lpae_t entry, mfn_t mfn, unsigned int flags)
> +static bool xen_pt_check_entry(lpae_t entry, mfn_t mfn, unsigned int level,
> + unsigned int flags)
> {
> - /* Sanity check when modifying a page. */
> + /* Sanity check when modifying an entry. */
> if ( (flags & _PAGE_PRESENT) && mfn_eq(mfn, INVALID_MFN) )
> {
> /* We don't allow modifying an invalid entry. */
> @@ -1072,6 +1073,13 @@ static bool xen_pt_check_entry(lpae_t entry, mfn_t mfn, unsigned int flags)
> return false;
> }
>
> + /* We don't allow modifying a table entry */
> + if ( !lpae_is_mapping(entry, level) )
> + {
> + mm_printk("Modifying a table entry is not allowed.\n");
> + return false;
> + }
> +
> /* We don't allow changing memory attributes. */
> if ( entry.pt.ai != PAGE_AI_MASK(flags) )
> {
> @@ -1087,7 +1095,7 @@ static bool xen_pt_check_entry(lpae_t entry, mfn_t mfn, unsigned int flags)
> return false;
> }
> }
> - /* Sanity check when inserting a page */
> + /* Sanity check when inserting a mapping */
> else if ( flags & _PAGE_PRESENT )
> {
> /* We should be here with a valid MFN. */
> @@ -1096,18 +1104,28 @@ static bool xen_pt_check_entry(lpae_t entry, mfn_t mfn, unsigned int flags)
> /* We don't allow replacing any valid entry. */
> if ( lpae_is_valid(entry) )
> {
> - mm_printk("Changing MFN for a valid entry is not allowed (%#"PRI_mfn" -> %#"PRI_mfn").\n",
> - mfn_x(lpae_get_mfn(entry)), mfn_x(mfn));
> + if ( lpae_is_mapping(entry, level) )
> + mm_printk("Changing MFN for a valid entry is not allowed (%#"PRI_mfn" -> %#"PRI_mfn").\n",
> + mfn_x(lpae_get_mfn(entry)), mfn_x(mfn));
> + else
> + mm_printk("Trying to replace a table with a mapping.\n");
> return false;
> }
> }
> - /* Sanity check when removing a page. */
> + /* Sanity check when removing a mapping. */
> else if ( (flags & (_PAGE_PRESENT|_PAGE_POPULATE)) == 0 )
> {
> /* We should be here with an invalid MFN. */
> ASSERT(mfn_eq(mfn, INVALID_MFN));
>
> - /* We don't allow removing page with contiguous bit set. */
> + /* We don't allow removing a table */
> + if ( lpae_is_table(entry, level) )
> + {
> + mm_printk("Removing a table is not allowed.\n");
> + return false;
> + }
> +
> + /* We don't allow removing a mapping with contiguous bit set. */
> if ( entry.pt.contig )
> {
> mm_printk("Removing entry with contiguous bit set is not allowed.\n");
> @@ -1125,13 +1143,13 @@ static bool xen_pt_check_entry(lpae_t entry, mfn_t mfn, unsigned int flags)
> return true;
> }
>
> +/* Update an entry at the level @target. */
> static int xen_pt_update_entry(mfn_t root, unsigned long virt,
> - mfn_t mfn, unsigned int flags)
> + mfn_t mfn, unsigned int target,
> + unsigned int flags)
> {
> int rc;
> unsigned int level;
> - /* We only support 4KB mapping (i.e level 3) for now */
> - unsigned int target = 3;
> lpae_t *table;
> /*
> * The intermediate page tables are read-only when the MFN is not valid
> @@ -1186,7 +1204,7 @@ static int xen_pt_update_entry(mfn_t root, unsigned long virt,
> entry = table + offsets[level];
>
> rc = -EINVAL;
> - if ( !xen_pt_check_entry(*entry, mfn, flags) )
> + if ( !xen_pt_check_entry(*entry, mfn, level, flags) )
> goto out;
>
> /* If we are only populating page-table, then we are done. */
> @@ -1204,8 +1222,11 @@ static int xen_pt_update_entry(mfn_t root, unsigned long virt,
> {
> pte = mfn_to_xen_entry(mfn, PAGE_AI_MASK(flags));
>
> - /* Third level entries set pte.pt.table = 1 */
> - pte.pt.table = 1;
> + /*
> + * First and second level pages set pte.pt.table = 0, but
> + * third level entries set pte.pt.table = 1.
> + */
> + pte.pt.table = (level == 3);
> }
> else /* We are updating the permission => Copy the current pte. */
> pte = *entry;
> @@ -1229,11 +1250,12 @@ static DEFINE_SPINLOCK(xen_pt_lock);
>
> static int xen_pt_update(unsigned long virt,
> mfn_t mfn,
> - unsigned long nr_mfns,
> + const unsigned long nr_mfns,
> unsigned int flags)
> {
> int rc = 0;
> - unsigned long addr = virt, addr_end = addr + nr_mfns * PAGE_SIZE;
> + unsigned long vfn = virt >> PAGE_SHIFT;
> + unsigned long left = nr_mfns;
>
> /*
> * For arm32, page-tables are different on each CPUs. Yet, they share
> @@ -1265,14 +1287,49 @@ static int xen_pt_update(unsigned long virt,
>
> spin_lock(&xen_pt_lock);
>
> - for ( ; addr < addr_end; addr += PAGE_SIZE )
> + while ( left )
> {
> - rc = xen_pt_update_entry(root, addr, mfn, flags);
> + unsigned int order, level;
> + unsigned long mask;
> +
> + /*
> + * Don't take into account the MFN when removing mapping (i.e
> + * MFN_INVALID) to calculate the correct target order.
> + *
> + * This loop relies on mfn, vfn, and nr_mfn to be all superpage
> + * aligned (mfn and vfn have to be architecturally), and it uses
> + * `mask` to check for that.
> + *
> + * XXX: Support superpage mappings if nr is not aligned to a
> + * superpage size.
> + */
> + mask = !mfn_eq(mfn, INVALID_MFN) ? mfn_x(mfn) : 0;
> + mask |= vfn | left;
> +
> + /*
> + * Always use level 3 mapping unless the caller request block
> + * mapping.
> + */
> + if ( likely(!(flags & _PAGE_BLOCK)) )
> + level = 3;
> + else if ( !(mask & (BIT(FIRST_ORDER, UL) - 1)) )
> + level = 1;
> + else if ( !(mask & (BIT(SECOND_ORDER, UL) - 1)) )
> + level = 2;
> + else
> + level = 3;
> +
> + order = LEVEL_ORDER(level);
> +
> + rc = xen_pt_update_entry(root, pfn_to_paddr(vfn), mfn, level, flags);
> if ( rc )
> break;
>
> + vfn += 1U << order;
> if ( !mfn_eq(mfn, INVALID_MFN) )
> - mfn = mfn_add(mfn, 1);
> + mfn = mfn_add(mfn, 1U << order);
> +
> + left -= (1U << order);
> }
>
> /*
> diff --git a/xen/include/asm-arm/page.h b/xen/include/asm-arm/page.h
> index 131507a51712..7052a87ec0fe 100644
> --- a/xen/include/asm-arm/page.h
> +++ b/xen/include/asm-arm/page.h
> @@ -69,6 +69,7 @@
> * [3:4] Permission flags
> * [5] Page present
> * [6] Only populate page tables
> + * [7] Superpage mappings is allowed
> */
> #define PAGE_AI_MASK(x) ((x) & 0x7U)
>
> @@ -82,6 +83,9 @@
> #define _PAGE_PRESENT (1U << 5)
> #define _PAGE_POPULATE (1U << 6)
>
> +#define _PAGE_BLOCK_BIT 7
> +#define _PAGE_BLOCK (1U << _PAGE_BLOCK_BIT)
> +
> /*
> * _PAGE_DEVICE and _PAGE_NORMAL are convenience defines. They are not
> * meant to be used outside of this header.
> --
> 2.17.1
>
next prev parent reply other threads:[~2021-05-11 22:43 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-25 20:13 [PATCH RFCv2 00/15] xen/arm: mm: Remove open-coding mappings Julien Grall
2021-04-25 20:13 ` [PATCH RFCv2 01/15] xen/arm: lpae: Rename LPAE_ENTRIES_MASK_GS to LPAE_ENTRY_MASK_GS Julien Grall
2021-05-11 22:12 ` Stefano Stabellini
2021-04-25 20:13 ` [PATCH RFCv2 02/15] xen/arm: lpae: Use the generic helpers to defined the Xen PT helpers Julien Grall
2021-05-11 22:26 ` Stefano Stabellini
2021-05-12 14:26 ` Julien Grall
2021-05-12 21:30 ` Stefano Stabellini
2021-05-12 22:16 ` Julien Grall
2021-05-13 22:44 ` Stefano Stabellini
2021-07-03 17:32 ` Julien Grall
2021-07-13 20:53 ` Stefano Stabellini
2021-07-14 17:40 ` Julien Grall
2021-04-25 20:13 ` [PATCH RFCv2 03/15] xen/arm: p2m: Replace level_{orders, masks} arrays with LEVEL_{ORDER, MASK} Julien Grall
2021-05-11 22:33 ` Stefano Stabellini
2021-05-12 14:39 ` Julien Grall
2021-04-25 20:13 ` [PATCH RFCv2 04/15] xen/arm: mm: Allow other mapping size in xen_pt_update_entry() Julien Grall
2021-05-11 22:42 ` Stefano Stabellini [this message]
2021-04-25 20:13 ` [PATCH RFCv2 05/15] xen/arm: mm: Avoid flushing the TLBs when mapping are inserted Julien Grall
2021-05-11 22:51 ` Stefano Stabellini
2021-04-25 20:13 ` [PATCH RFCv2 06/15] xen/arm: mm: Don't open-code Xen PT update in remove_early_mappings() Julien Grall
2021-05-11 22:58 ` Stefano Stabellini
2021-04-25 20:13 ` [PATCH RFCv2 07/15] xen/arm: mm: Re-implement early_fdt_map() using map_pages_to_xen() Julien Grall
2021-05-12 21:41 ` Stefano Stabellini
2021-05-12 22:18 ` Julien Grall
2021-04-25 20:13 ` [PATCH RFCv2 08/15] xen/arm32: mm: Check if the virtual address is shared before updating it Julien Grall
2021-05-12 22:00 ` Stefano Stabellini
2021-05-12 22:23 ` Julien Grall
2021-05-13 22:32 ` Stefano Stabellini
2021-05-13 22:59 ` Julien Grall
2021-05-14 1:04 ` Stefano Stabellini
2021-04-25 20:13 ` [PATCH RFCv2 09/15] xen/arm32: mm: Re-implement setup_xenheap_mappings() using map_pages_to_xen() Julien Grall
2021-05-12 22:07 ` Stefano Stabellini
2021-05-13 17:55 ` Julien Grall
2021-04-25 20:13 ` [PATCH RFCv2 10/15] xen/arm: mm: Allocate xen page tables in domheap rather than xenheap Julien Grall
2021-05-12 22:44 ` Stefano Stabellini
2021-05-13 18:09 ` Julien Grall
2021-05-13 22:27 ` Stefano Stabellini
2021-05-15 8:48 ` Julien Grall
2021-05-18 0:37 ` Stefano Stabellini
2021-04-25 20:13 ` [PATCH RFCv2 11/15] xen/arm: mm: Allow page-table allocation from the boot allocator Julien Grall
2021-05-13 22:58 ` Stefano Stabellini
2021-04-25 20:13 ` [PATCH RFCv2 12/15] xen/arm: add Persistent Map (PMAP) infrastructure Julien Grall
2021-04-26 9:41 ` Xia, Hongyan
2021-07-03 17:57 ` Julien Grall
2021-04-28 21:47 ` Wei Liu
2021-05-14 23:25 ` Stefano Stabellini
2021-05-15 8:54 ` Julien Grall
2021-04-25 20:13 ` [PATCH RFCv2 13/15] xen/arm: mm: Use the PMAP helpers in xen_{,un}map_table() Julien Grall
2021-05-14 23:35 ` Stefano Stabellini
2021-05-15 9:03 ` Julien Grall
2021-04-25 20:13 ` [PATCH RFCv2 14/15] xen/arm: mm: Rework setup_xenheap_mappings() Julien Grall
2021-05-14 23:51 ` Stefano Stabellini
2021-05-15 9:21 ` Julien Grall
2021-05-18 0:50 ` Stefano Stabellini
2022-02-12 19:16 ` Julien Grall
2021-04-25 20:13 ` [PATCH RFCv2 15/15] xen/arm: mm: Re-implement setup_frame_table_mappings() with map_pages_to_xen() Julien Grall
2021-05-15 0:02 ` Stefano Stabellini
2021-05-15 9:25 ` Julien Grall
2021-05-18 0:51 ` Stefano Stabellini
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=alpine.DEB.2.21.2105111542290.5018@sstabellini-ThinkPad-T480s \
--to=sstabellini@kernel.org \
--cc=Bertrand.Marquis@arm.com \
--cc=Henry.Wang@arm.com \
--cc=Penny.Zheng@arm.com \
--cc=Volodymyr_Babchuk@epam.com \
--cc=Wei.Chen@arm.com \
--cc=jgrall@amazon.com \
--cc=julien.grall@arm.com \
--cc=julien@xen.org \
--cc=xen-devel@lists.xenproject.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).