From: Julien Grall <julien@xen.org>
To: Oleksandr Tyshchenko <olekstysh@gmail.com>,
xen-devel@lists.xenproject.org
Cc: "Oleksandr Tyshchenko" <oleksandr_tyshchenko@epam.com>,
"Andrew Cooper" <andrew.cooper3@citrix.com>,
"George Dunlap" <george.dunlap@citrix.com>,
"Ian Jackson" <ian.jackson@eu.citrix.com>,
"Jan Beulich" <jbeulich@suse.com>,
"Stefano Stabellini" <sstabellini@kernel.org>,
"Wei Liu" <wl@xen.org>, "Roger Pau Monné" <roger.pau@citrix.com>,
"Paul Durrant" <paul@xen.org>,
"Jun Nakajima" <jun.nakajima@intel.com>,
"Kevin Tian" <kevin.tian@intel.com>, "Tim Deegan" <tim@xen.org>,
"Julien Grall" <julien.grall@arm.com>
Subject: Re: [PATCH V1 02/16] xen/ioreq: Make x86's IOREQ feature common
Date: Thu, 24 Sep 2020 19:01:23 +0100 [thread overview]
Message-ID: <3997a705-ccb1-4b8f-41ca-c5507360c759@xen.org> (raw)
In-Reply-To: <1599769330-17656-3-git-send-email-olekstysh@gmail.com>
On 10/09/2020 21:21, Oleksandr Tyshchenko wrote:
> +static bool hvm_wait_for_io(struct hvm_ioreq_vcpu *sv, ioreq_t *p)
> +{
> + unsigned int prev_state = STATE_IOREQ_NONE;
> + unsigned int state = p->state;
> + uint64_t data = ~0;
> +
> + smp_rmb();
> +
> + /*
> + * The only reason we should see this condition be false is when an
> + * emulator dying races with I/O being requested.
> + */
> + while ( likely(state != STATE_IOREQ_NONE) )
> + {
> + if ( unlikely(state < prev_state) )
> + {
> + gdprintk(XENLOG_ERR, "Weird HVM ioreq state transition %u -> %u\n",
> + prev_state, state);
> + sv->pending = false;
> + domain_crash(sv->vcpu->domain);
> + return false; /* bail */
> + }
> +
> + switch ( prev_state = state )
> + {
> + case STATE_IORESP_READY: /* IORESP_READY -> NONE */
> + p->state = STATE_IOREQ_NONE;
> + data = p->data;
> + break;
> +
> + case STATE_IOREQ_READY: /* IOREQ_{READY,INPROCESS} -> IORESP_READY */
> + case STATE_IOREQ_INPROCESS:
> + wait_on_xen_event_channel(sv->ioreq_evtchn,
> + ({ state = p->state;
> + smp_rmb();
> + state != prev_state; }));
> + continue;
As I pointed out previously [1], this helper was implemented with the
expectation that wait_on_xen_event_channel() will not return if the vCPU
got rescheduled.
However, this assumption doesn't hold on Arm.
I can see two solution:
1) Re-execute the caller
2) Prevent an IOREQ to disappear until the loop finish.
@Paul any opinions?
Cheers,
[1]
https://lore.kernel.org/xen-devel/6bfc3920-8f29-188c-cff4-2b99dabe166f@xen.org/
--
Julien Grall
next prev parent reply other threads:[~2020-09-24 18:02 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 [this message]
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
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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