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From: "Jan Beulich" <JBeulich@suse.com>
To: Julien Grall <julien.grall@arm.com>
Cc: Tim Deegan <tim@xen.org>,
	Stefano Stabellini <sstabellini@kernel.org>,
	Wei Liu <wei.liu2@citrix.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
	George Dunlap <George.Dunlap@eu.citrix.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	Ian Jackson <Ian.Jackson@eu.citrix.com>,
	andre.przywara@linaro.org, xen-devel@lists.xen.org
Subject: Re: [RFC 16/16] xen/arm: Track page accessed between batch of Set/Way operations
Date: Tue, 09 Oct 2018 01:04:01 -0600	[thread overview]
Message-ID: <5BBC52E102000078001EFD56@prv1-mh.provo.novell.com> (raw)
In-Reply-To: <20181008183352.16291-17-julien.grall@arm.com>

>>> On 08.10.18 at 20:33, <julien.grall@arm.com> wrote:
> At the moment, the implementation of Set/Way operations will go through
> all the entries of the guest P2M and flush them. However, this is very
> expensive and may render unusable a guest OS using them.
> 
> For instance, Linux 32-bit will use Set/Way operations during secondary
> CPU bring-up. As the implementation is really expensive, it may be possible
> to hit the CPU bring-up timeout.
> 
> To limit the Set/Way impact, we track what pages has been of the guest
> has been accessed between batch of Set/Way operations. This is done
> using bit[0] (aka valid bit) of the P2M entry.
> 
> This patch adds a new per-arch helper is introduced to perform actions just
> before the guest is first unpaused. This will be used to invalidate the
> P2M to track access from the start of the guest.

While I'm not opposed to the new arch hook, why don't you create the
p2m entries in their intended state right away? At the very least this
would have the benefit of confining the entire change to Arm code.

Jan



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  reply	other threads:[~2018-10-09  7:04 UTC|newest]

Thread overview: 62+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-08 18:33 [RFC 00/16] xen/arm: Implement Set/Way operations Julien Grall
2018-10-08 18:33 ` [RFC 01/16] xen/arm: Introduce helpers to clear/flags flags in HCR_EL2 Julien Grall
2018-10-08 18:33 ` [RFC 02/16] xen/arm: Introduce helpers to get/set an MFN from/to an LPAE entry Julien Grall
2018-10-30  0:07   ` Stefano Stabellini
2018-10-08 18:33 ` [RFC 03/16] xen/arm: Allow lpae_is_{table, mapping} helpers to work on invalid entry Julien Grall
2018-10-30  0:10   ` Stefano Stabellini
2018-10-08 18:33 ` [RFC 04/16] xen/arm: guest_walk_tables: Switch the return to bool Julien Grall
2018-10-08 18:33 ` [RFC 05/16] xen/arm: traps: Move the implementation of GUEST_BUG_ON in traps.h Julien Grall
2018-10-30  0:11   ` Stefano Stabellini
2018-10-08 18:33 ` [RFC 06/16] xen/arm: p2m: Introduce a helper to generate P2M table entry from a page Julien Grall
2018-10-30  0:14   ` Stefano Stabellini
2018-10-08 18:33 ` [RFC 07/16] xen/arm: p2m: Introduce p2m_is_valid and use it Julien Grall
2018-10-30  0:21   ` Stefano Stabellini
2018-10-30 11:02     ` Julien Grall
2018-11-02 22:45       ` Stefano Stabellini
2018-10-08 18:33 ` [RFC 08/16] xen/arm: p2m: Handle translation fault in get_page_from_gva Julien Grall
2018-10-30  0:47   ` Stefano Stabellini
2018-10-30 11:24     ` Julien Grall
2018-10-08 18:33 ` [RFC 09/16] xen/arm: p2m: Introduce a function to resolve translation fault Julien Grall
2018-11-02 23:27   ` Stefano Stabellini
2018-11-05 11:55     ` Julien Grall
2018-11-05 17:56       ` Stefano Stabellini
2018-11-06 14:20         ` Julien Grall
2018-11-12 17:59           ` Julien Grall
2018-11-12 23:36             ` Stefano Stabellini
2018-12-04 15:35               ` Julien Grall
2018-12-04 19:13                 ` Stefano Stabellini
2018-10-08 18:33 ` [RFC 10/16] xen/arm: vcpreg: Add wrappers to handle co-proc access trapped by HCR_EL2.TVM Julien Grall
2018-11-05 19:47   ` Stefano Stabellini
2018-11-05 23:21     ` Julien Grall
2018-11-06 17:36       ` Stefano Stabellini
2018-11-06 17:52         ` Julien Grall
2018-11-06 17:56           ` Stefano Stabellini
2018-12-04 16:24       ` Julien Grall
2018-10-08 18:33 ` [RFC 11/16] xen/arm: vsysreg: Add wrapper to handle sysreg " Julien Grall
2018-11-05 20:42   ` Stefano Stabellini
2018-10-08 18:33 ` [RFC 12/16] xen/arm: Rework p2m_cache_flush to take a range [begin, end) Julien Grall
2018-11-02 23:38   ` Stefano Stabellini
2018-10-08 18:33 ` [RFC 13/16] xen/arm: p2m: Allow to flush cache on any RAM region Julien Grall
2018-11-02 23:40   ` Stefano Stabellini
2018-10-08 18:33 ` [RFC 14/16] xen/arm: p2m: Extend p2m_get_entry to return the value of bit[0] (valid bit) Julien Grall
2018-11-02 23:44   ` Stefano Stabellini
2018-11-05 11:56     ` Julien Grall
2018-11-05 17:31       ` Stefano Stabellini
2018-11-05 17:32         ` Julien Grall
2018-10-08 18:33 ` [RFC 15/16] xen/arm: Implement Set/Way operations Julien Grall
2018-11-05 21:10   ` Stefano Stabellini
2018-11-05 23:38     ` Julien Grall
2018-11-06 17:31       ` Stefano Stabellini
2018-11-06 17:34         ` Julien Grall
2018-11-06 17:38           ` Stefano Stabellini
2018-10-08 18:33 ` [RFC 16/16] xen/arm: Track page accessed between batch of " Julien Grall
2018-10-09  7:04   ` Jan Beulich [this message]
2018-10-09 10:16     ` Julien Grall
2018-10-09 11:43       ` Jan Beulich
2018-10-09 12:24         ` Julien Grall
2018-11-05 21:35   ` Stefano Stabellini
2018-11-05 23:28     ` Julien Grall
2018-11-06 17:43       ` Stefano Stabellini
2018-11-06 18:10         ` Julien Grall
2018-11-06 18:41           ` Stefano Stabellini
2018-11-22 14:21 ` [RFC 00/16] xen/arm: Implement " Julien Grall

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