commit 2df1aa01bef7366798248ac6d03cfb42048b003d
Author: Paul Durrant <paul.durr...@citrix.com>
Date: Tue Jun 23 18:07:49 2015 +0200
x86/hvm: remove hvm_io_pending() check in hvmemul_do_io()
...
- rc = X86EMUL_RETRY;
- if ( !hvm_send_assist_req(s, &p) )
+ rc = hvm_send_assist_req(s, &p);
+ if ( rc != X86EMUL_RETRY )
...
if ( unlikely(!vcpu_start_shutdown_deferral(curr)) )
- return 0; /* implicitly bins the i/o operation */
+ return X86EMUL_OKAY;
So now X86EMUL_OKAY is returned from hvmemul_do_io() during shutdown.
From Jan Beulich about this:
Re: [Xen-devel] [PATCH 3/5] hvmemul_do_io: If the send to the ioreq
server failed do not retry.
<https://www.mail-archive.com/search?l=xen-devel@lists.xen.org&q=subject:%22Re%5C%3A+%5C%5BXen%5C-devel%5C%5D+%5C%5BPATCH+3%5C%2F5%5C%5D+hvmemul_do_io%5C%3A+If+the+send+to+the+ioreq+server+failed+do+not+retry.%22&o=newest>
Jan Beulich
<https://www.mail-archive.com/search?l=xen-devel@lists.xen.org&q=from:%22Jan+Beulich%22>
Fri, 30 Jan 2015 02:24:55 -0800
<https://www.mail-archive.com/search?l=xen-devel@lists.xen.org&q=date:20150130>
On 30.01.15 at 01:52, <dsl...@verizon.com> wrote:
I.E. do just what no backing DM does.
_If_ this is correct, the if() modified here should be folded with the
one a few lines up. But looking at the description of the commit that
introduced this (bac0999325 "x86 hvm: Do not incorrectly retire an
instruction emulation...", almost immediately modified by f20f3c8ece
"x86 hvm: On failed hvm_send_assist_req(), io emulation...") I doubt
this is really what we want, or at the very least your change
description should explain what was wrong with the original commit.
Jan
going up the call stack:
in handle_pio when hvmemul_do_pio_buffer() returns X86EMUL_OKAY, it
returns 1.
svm_vmexit_handler 2578 if ( handle_pio(port, bytes, dir) )
or
vmx_vmexit_handler 3178 if ( handle_pio(port, bytes, dir) )
both update the IP in this case which is wrong during shutdown.
So I think:
rc = hvm_send_assist_req(s, &p);
if ( rc != X86EMUL_RETRY )
vio->io_state = HVMIO_none;
needs to change to:
rc = hvm_send_assist_req(s, &p);
if ( rc != X86EMUL_RETRY )
{
vio->io_state = HVMIO_none;
if ( rc == X86EMUL_OKAY )
rc = X86EMUL_RETRY;
}
-Don Slutz
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