From: Oleksandr <olekstysh@gmail.com>
To: Jan Beulich <jbeulich@suse.com>
Cc: "Paul Durrant" <paul@xen.org>,
xen-devel@lists.xenproject.org,
"Oleksandr Tyshchenko" <oleksandr_tyshchenko@epam.com>,
"Stefano Stabellini" <sstabellini@kernel.org>,
"Julien Grall" <julien@xen.org>,
"Volodymyr Babchuk" <Volodymyr_Babchuk@epam.com>,
"Andrew Cooper" <andrew.cooper3@citrix.com>,
"Wei Liu" <wl@xen.org>, "Roger Pau Monné" <roger.pau@citrix.com>,
"Julien Grall" <julien.grall@arm.com>
Subject: Re: [PATCH V1 11/16] xen/ioreq: Introduce hvm_domain_has_ioreq_server()
Date: Tue, 22 Sep 2020 21:23:33 +0300 [thread overview]
Message-ID: <3b85d5b1-1b34-3128-e4ac-c939ef65f74f@gmail.com> (raw)
In-Reply-To: <93cc6603-44f2-1ceb-997d-cbc51c3ba2c3@suse.com>
On 16.09.20 11:04, Jan Beulich wrote:
Hi Jan
> On 10.09.2020 22:22, Oleksandr Tyshchenko wrote:
>> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
>>
>> This patch introduces a helper the main purpose of which is to check
>> if a domain is using IOREQ server(s).
>>
>> On Arm the benefit is to avoid calling handle_hvm_io_completion()
>> (which implies iterating over all possible IOREQ servers anyway)
>> on every return in leave_hypervisor_to_guest() if there is no active
>> servers for the particular domain.
>>
>> This involves adding an extra per-domain variable to store the count
>> of servers in use.
> Since only Arm needs the variable (and the helper), perhaps both should
> be Arm-specific (which looks to be possible without overly much hassle)?
Please note that the whole ioreq_server struct are going be moved to
"common" domain and new variable is going to go into it.
I am wondering whether this single-line helper could be used on x86 or
potential new arch ...
>
>> --- a/xen/common/ioreq.c
>> +++ b/xen/common/ioreq.c
>> @@ -38,9 +38,15 @@ static void set_ioreq_server(struct domain *d, unsigned int id,
>> struct hvm_ioreq_server *s)
>> {
>> ASSERT(id < MAX_NR_IOREQ_SERVERS);
>> - ASSERT(!s || !d->arch.hvm.ioreq_server.server[id]);
>> + ASSERT((!s && d->arch.hvm.ioreq_server.server[id]) ||
>> + (s && !d->arch.hvm.ioreq_server.server[id]));
> For one, this can be had with less redundancy (and imo even improved
> clarity, but I guess this latter aspect my depend on personal
> preferences):
>
> ASSERT(d->arch.hvm.ioreq_server.server[id] ? !s : !!s);
This construction indeed better.
>
> But then I wonder whether the original intention wasn't rather such
> that replacing NULL by NULL is permissible. Paul?
>
>> d->arch.hvm.ioreq_server.server[id] = s;
>> +
>> + if ( s )
>> + d->arch.hvm.ioreq_server.nr_servers ++;
>> + else
>> + d->arch.hvm.ioreq_server.nr_servers --;
> Nit: Stray blanks (should be there only with binary operators).
ok
>
>> @@ -1395,6 +1401,7 @@ unsigned int hvm_broadcast_ioreq(ioreq_t *p, bool buffered)
>> void hvm_ioreq_init(struct domain *d)
>> {
>> spin_lock_init(&d->arch.hvm.ioreq_server.lock);
>> + d->arch.hvm.ioreq_server.nr_servers = 0;
> There's no need for this - struct domain instances start out all
> zero anyway.
ok
>
>> --- a/xen/include/xen/ioreq.h
>> +++ b/xen/include/xen/ioreq.h
>> @@ -57,6 +57,11 @@ struct hvm_ioreq_server {
>> uint8_t bufioreq_handling;
>> };
>>
>> +static inline bool hvm_domain_has_ioreq_server(const struct domain *d)
>> +{
>> + return (d->arch.hvm.ioreq_server.nr_servers > 0);
>> +}
> This is safe only when d == current->domain and it's not paused,
> or when they're distinct and d is paused. Otherwise the result is
> stale before the caller can inspect it. This wants documenting by
> at least a comment, but perhaps better by suitable ASSERT()s.
Agree, will use ASSERT()s.
>
> As in earlier patches I don't think a hvm_ prefix should be used
> here.
ok
>
> Also as a nit: The parentheses here are unnecessary, and strictly
> speaking the "> 0" is, too.
ok
--
Regards,
Oleksandr Tyshchenko
next prev parent reply other threads:[~2020-09-22 18:23 UTC|newest]
Thread overview: 111+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-10 20:21 [PATCH V1 00/16] IOREQ feature (+ virtio-mmio) on Arm Oleksandr Tyshchenko
2020-09-10 20:21 ` [PATCH V1 01/16] x86/ioreq: Prepare IOREQ feature for making it common Oleksandr Tyshchenko
2020-09-14 13:52 ` Jan Beulich
2020-09-21 12:22 ` Oleksandr
2020-09-21 12:31 ` Jan Beulich
2020-09-21 12:47 ` Oleksandr
2020-09-21 13:29 ` Jan Beulich
2020-09-21 14:43 ` Oleksandr
2020-09-21 15:28 ` Jan Beulich
2020-09-23 17:22 ` Julien Grall
2020-09-23 18:08 ` Oleksandr
2020-09-10 20:21 ` [PATCH V1 02/16] xen/ioreq: Make x86's IOREQ feature common Oleksandr Tyshchenko
2020-09-14 14:17 ` Jan Beulich
2020-09-21 19:02 ` Oleksandr
2020-09-22 6:33 ` Jan Beulich
2020-09-22 9:58 ` Oleksandr
2020-09-22 10:54 ` Jan Beulich
2020-09-22 15:05 ` Oleksandr
2020-09-22 15:52 ` Jan Beulich
2020-09-23 12:28 ` Oleksandr
2020-09-24 10:58 ` Jan Beulich
2020-09-24 15:38 ` Oleksandr
2020-09-24 15:51 ` Jan Beulich
2020-09-24 18:01 ` Julien Grall
2020-09-25 8:19 ` Paul Durrant
2020-09-30 13:39 ` Oleksandr
2020-09-30 17:47 ` Julien Grall
2020-10-01 6:59 ` Paul Durrant
2020-10-01 8:49 ` Jan Beulich
2020-10-01 8:50 ` Paul Durrant
2020-09-10 20:21 ` [PATCH V1 03/16] xen/ioreq: Make x86's hvm_ioreq_needs_completion() common Oleksandr Tyshchenko
2020-09-14 14:59 ` Jan Beulich
2020-09-22 16:16 ` Oleksandr
2020-09-23 17:27 ` Julien Grall
2020-09-10 20:21 ` [PATCH V1 04/16] xen/ioreq: Provide alias for the handle_mmio() Oleksandr Tyshchenko
2020-09-14 15:10 ` Jan Beulich
2020-09-22 16:20 ` Oleksandr
2020-09-23 17:28 ` Julien Grall
2020-09-23 18:17 ` Oleksandr
2020-09-10 20:21 ` [PATCH V1 05/16] xen/ioreq: Make x86's hvm_mmio_first(last)_byte() common Oleksandr Tyshchenko
2020-09-14 15:13 ` Jan Beulich
2020-09-22 16:24 ` Oleksandr
2020-09-10 20:22 ` [PATCH V1 06/16] xen/ioreq: Make x86's hvm_ioreq_(page/vcpu/server) structs common Oleksandr Tyshchenko
2020-09-14 15:16 ` Jan Beulich
2020-09-14 15:59 ` Julien Grall
2020-09-22 16:33 ` Oleksandr
2020-09-10 20:22 ` [PATCH V1 07/16] xen/dm: Make x86's DM feature common Oleksandr Tyshchenko
2020-09-14 15:56 ` Jan Beulich
2020-09-22 16:46 ` Oleksandr
2020-09-24 11:03 ` Jan Beulich
2020-09-24 12:47 ` Oleksandr
2020-09-23 17:35 ` Julien Grall
2020-09-23 18:28 ` Oleksandr
2020-09-10 20:22 ` [PATCH V1 08/16] xen/mm: Make x86's XENMEM_resource_ioreq_server handling common Oleksandr Tyshchenko
2020-09-10 20:22 ` [PATCH V1 09/16] arm/ioreq: Introduce arch specific bits for IOREQ/DM features Oleksandr Tyshchenko
2020-09-11 10:14 ` Oleksandr
2020-09-16 7:51 ` Jan Beulich
2020-09-22 17:12 ` Oleksandr
2020-09-23 18:03 ` Julien Grall
2020-09-23 20:16 ` Oleksandr
2020-09-24 11:08 ` Jan Beulich
2020-09-24 16:02 ` Oleksandr
2020-09-24 18:02 ` Oleksandr
2020-09-25 6:51 ` Jan Beulich
2020-09-25 9:47 ` Oleksandr
2020-09-26 13:12 ` Julien Grall
2020-09-26 13:18 ` Oleksandr
2020-09-24 16:51 ` Julien Grall
2020-09-24 17:25 ` Julien Grall
2020-09-24 18:22 ` Oleksandr
2020-09-26 13:21 ` Julien Grall
2020-09-26 14:57 ` Oleksandr
2020-09-10 20:22 ` [PATCH V1 10/16] xen/mm: Handle properly reference in set_foreign_p2m_entry() on Arm Oleksandr Tyshchenko
2020-09-16 7:17 ` Jan Beulich
2020-09-16 8:50 ` Julien Grall
2020-09-16 8:52 ` Jan Beulich
2020-09-16 8:55 ` Julien Grall
2020-09-22 17:30 ` Oleksandr
2020-09-16 8:08 ` Jan Beulich
2020-09-10 20:22 ` [PATCH V1 11/16] xen/ioreq: Introduce hvm_domain_has_ioreq_server() Oleksandr Tyshchenko
2020-09-16 8:04 ` Jan Beulich
2020-09-16 8:13 ` Paul Durrant
2020-09-16 8:39 ` Julien Grall
2020-09-16 8:43 ` Paul Durrant
2020-09-22 18:39 ` Oleksandr
2020-09-22 18:23 ` Oleksandr [this message]
2020-09-10 20:22 ` [PATCH V1 12/16] xen/dm: Introduce xendevicemodel_set_irq_level DM op Oleksandr Tyshchenko
2020-09-26 13:50 ` Julien Grall
2020-09-26 14:21 ` Oleksandr
2020-09-10 20:22 ` [PATCH V1 13/16] xen/ioreq: Make x86's invalidate qemu mapcache handling common Oleksandr Tyshchenko
2020-09-16 8:50 ` Jan Beulich
2020-09-22 19:32 ` Oleksandr
2020-09-24 11:16 ` Jan Beulich
2020-09-24 16:45 ` Oleksandr
2020-09-25 7:03 ` Jan Beulich
2020-09-25 13:05 ` Oleksandr
2020-10-02 9:55 ` Oleksandr
2020-10-07 10:38 ` Julien Grall
2020-10-07 12:01 ` Oleksandr
2020-09-10 20:22 ` [PATCH V1 14/16] xen/ioreq: Use guest_cmpxchg64() instead of cmpxchg() Oleksandr Tyshchenko
2020-09-16 9:04 ` Jan Beulich
2020-09-16 9:07 ` Julien Grall
2020-09-16 9:09 ` Paul Durrant
2020-09-16 9:12 ` Julien Grall
2020-09-22 20:05 ` Oleksandr
2020-09-23 18:12 ` Julien Grall
2020-09-23 20:29 ` Oleksandr
2020-09-16 9:07 ` Paul Durrant
2020-09-23 18:05 ` Julien Grall
2020-09-10 20:22 ` [PATCH V1 15/16] libxl: Introduce basic virtio-mmio support on Arm Oleksandr Tyshchenko
2020-09-10 20:22 ` [PATCH V1 16/16] [RFC] libxl: Add support for virtio-disk configuration Oleksandr Tyshchenko
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