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From: Jan Beulich <jbeulich@suse.com>
To: Hongyan Xia <hx242@xen.org>
Cc: jgrall@amazon.com, "Andrew Cooper" <andrew.cooper3@citrix.com>,
	"Roger Pau Monné" <roger.pau@citrix.com>, "Wei Liu" <wl@xen.org>,
	xen-devel@lists.xenproject.org
Subject: Re: [PATCH v10 01/13] x86/mm: rewrite virt_to_xen_l*e
Date: Thu, 22 Apr 2021 13:54:30 +0200	[thread overview]
Message-ID: <b667c7ab-b12d-d46a-9318-925c4a19faaa@suse.com> (raw)
In-Reply-To: <0ccd3883b0ec2e05d600bb593f8f0afd058adc43.1619014052.git.hongyxia@amazon.com>

On 21.04.2021 16:15, Hongyan Xia wrote:
> From: Wei Liu <wei.liu2@citrix.com>
> 
> Rewrite those functions to use the new APIs. Modify its callers to unmap
> the pointer returned. Since alloc_xen_pagetable_new() is almost never
> useful unless accompanied by page clearing and a mapping, introduce a
> helper alloc_map_clear_xen_pt() for this sequence.
> 
> Signed-off-by: Wei Liu <wei.liu2@citrix.com>
> Signed-off-by: Hongyan Xia <hongyxia@amazon.com>

Reviewed-by: Jan Beulich <jbeulich@suse.com>
albeit ...

> @@ -4941,33 +4961,33 @@ static l3_pgentry_t *virt_to_xen_l3e(unsigned long v)
>      if ( !(l4e_get_flags(*pl4e) & _PAGE_PRESENT) )
>      {
>          bool locking = system_state > SYS_STATE_boot;
> -        l3_pgentry_t *l3t = alloc_xen_pagetable();
> +        mfn_t l3mfn;
> +        l3_pgentry_t *l3t = alloc_mapped_pagetable(&l3mfn);
>  
>          if ( !l3t )
>              return NULL;
> -        clear_page(l3t);
> +        UNMAP_DOMAIN_PAGE(l3t);

... this immediate unmapping (and then re-mapping below) will imo
want re-doing down the road as well. Even if it's not a severe
performance hit, it's simply odd, at least to me.

Jan


  reply	other threads:[~2021-04-22 11:54 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-21 14:15 [PATCH v10 00/13] switch to domheap for Xen page tables Hongyan Xia
2021-04-21 14:15 ` [PATCH v10 01/13] x86/mm: rewrite virt_to_xen_l*e Hongyan Xia
2021-04-22 11:54   ` Jan Beulich [this message]
2021-04-21 14:15 ` [PATCH v10 02/13] x86/mm: switch to new APIs in map_pages_to_xen Hongyan Xia
2021-04-22 12:01   ` Jan Beulich
2021-04-21 14:15 ` [PATCH v10 03/13] x86/mm: switch to new APIs in modify_xen_mappings Hongyan Xia
2021-04-22 13:10   ` Hongyan Xia
2021-04-21 14:15 ` [PATCH v10 04/13] x86_64/mm: introduce pl2e in paging_init Hongyan Xia
2021-04-21 14:15 ` [PATCH v10 05/13] x86_64/mm: switch to new APIs " Hongyan Xia
2021-04-21 14:15 ` [PATCH v10 06/13] x86_64/mm: switch to new APIs in setup_m2p_table Hongyan Xia
2021-04-21 14:15 ` [PATCH v10 07/13] efi: use new page table APIs in copy_mapping Hongyan Xia
2021-04-21 14:15 ` [PATCH v10 08/13] efi: switch to new APIs in EFI code Hongyan Xia
2021-04-21 14:15 ` [PATCH v10 09/13] x86/smpboot: add exit path for clone_mapping() Hongyan Xia
2021-04-21 14:15 ` [PATCH v10 10/13] x86/smpboot: switch clone_mapping() to new APIs Hongyan Xia
2021-04-21 14:15 ` [PATCH v10 11/13] x86/mm: drop old page table APIs Hongyan Xia
2021-04-21 14:15 ` [PATCH v10 12/13] x86: switch to use domheap page for page tables Hongyan Xia
2021-04-21 14:15 ` [PATCH v10 13/13] x86/mm: drop _new suffix for page table APIs Hongyan Xia
2021-04-22 16:21 ` [PATCH v10 00/13] switch to domheap for Xen page tables Andrew Cooper
2021-04-22 16:35   ` Hongyan Xia
2021-04-22 17:27     ` Julien Grall
2021-04-22 17:28     ` Andrew Cooper

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