From: Razvan Cojocaru <rcojocaru@bitdefender.com>
To: Alexandru Stefan ISAILA <aisaila@bitdefender.com>,
Jan Beulich <JBeulich@suse.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
Tamas K Lengyel <tamas@tklengyel.com>,
Wei Liu <wei.liu2@citrix.com>,
xen-devel <xen-devel@lists.xenproject.org>
Subject: Re: [PATCH v3] arch/x86: Add registers to vm_event
Date: Thu, 25 Oct 2018 16:33:29 +0300 [thread overview]
Message-ID: <0bd1661d-26a9-a256-2e32-d6a85c8cf322@bitdefender.com> (raw)
In-Reply-To: <a2d6bd10-ca33-ad1c-2988-b85853e9a613@bitdefender.com>
On 10/25/18 4:10 PM, Alexandru Stefan ISAILA wrote:
> On 25.10.2018 14:55, Jan Beulich wrote:
>>>>> On 18.10.18 at 11:02, <aisaila@bitdefender.com> wrote:
>>> +struct x86_selector_reg {
>>> + union
>>> + {
>>> + uint64_t bytes;
>>> + struct
>>> + {
>>> + uint32_t base;
>>> + uint32_t limit : 20;
>>> + uint32_t ar : 12;
>>> + } fields;
>>> + };
>>> +};
>>
>> I don't understand why sel was moved out. Are you tight on
>> space here, such that you can't tolerate the padding bytes?
>
> It was dropped on Andrew's suggestion. We are ok with it in the
> structure so if is ok by you I can add it back.
We are tight on space. The ring buffer is only 4K, and it already can
only fit about 10 sync vm_events before VCPUs need to be blocked waiting
for a place in the buffer. That's why we've attempted the packing.
>> Finally - what meaning to the low (or high) 4 bits of "ar"
>> carry?
>
> If I correctly understand the question, we use ar bits to determine the
> running mode of the guest.
That's what we need the CS .ar for: looking at CS_AR_BYTES_D and
CS_AR_BYTES_L, the rest we pass along to the introspection engine - I'd
have to check with them for more details if requested.
But I think we've probably misunderstood the question.
Thanks,
Razvan
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next prev parent reply other threads:[~2018-10-25 13:33 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-18 9:02 [PATCH v3] arch/x86: Add registers to vm_event Alexandru Stefan ISAILA
2018-10-18 19:56 ` Tamas K Lengyel
2018-10-23 8:36 ` PING: " Alexandru Stefan ISAILA
2018-10-24 16:48 ` Tamas K Lengyel
2018-10-25 7:16 ` Alexandru Stefan ISAILA
2018-10-25 11:55 ` Jan Beulich
2018-10-25 13:10 ` Alexandru Stefan ISAILA
2018-10-25 13:33 ` Razvan Cojocaru [this message]
2018-10-25 14:04 ` Jan Beulich
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