From: Jan Beulich <jbeulich@suse.com>
To: Julien Grall <julien@xen.org>
Cc: "Kevin Tian" <kevin.tian@intel.com>,
"Stefano Stabellini" <sstabellini@kernel.org>,
tamas.lengyel@intel.com, "Wei Liu" <wl@xen.org>,
"Andrew Cooper" <andrew.cooper3@citrix.com>,
"Michał Leszczyński" <michal.leszczynski@cert.pl>,
"Ian Jackson" <ian.jackson@eu.citrix.com>,
"George Dunlap" <george.dunlap@citrix.com>,
"Jun Nakajima" <jun.nakajima@intel.com>,
xen-devel@lists.xenproject.org, luwei.kang@intel.com,
"Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [PATCH v4 02/10] x86/vmx: add IPT cpu feature
Date: Thu, 2 Jul 2020 16:17:06 +0200 [thread overview]
Message-ID: <7ac383c2-0264-cc75-a85b-13c1fdfb0bd6@suse.com> (raw)
In-Reply-To: <7f915146-6566-e5a7-14d2-cb2319838562@xen.org>
On 02.07.2020 16:14, Julien Grall wrote:
> Hi,
>
> On 02/07/2020 14:30, Jan Beulich wrote:
>> On 02.07.2020 11:57, Julien Grall wrote:
>>> Hi,
>>>
>>> On 02/07/2020 10:18, Jan Beulich wrote:
>>>> On 02.07.2020 10:54, Julien Grall wrote:
>>>>>
>>>>>
>>>>> On 02/07/2020 09:50, Jan Beulich wrote:
>>>>>> On 02.07.2020 10:42, Julien Grall wrote:
>>>>>>> On 02/07/2020 09:29, Jan Beulich wrote:
>>>>>>>> I'm with Andrew here, fwiw, as long as the little bit of code that
>>>>>>>> is actually put in common/ or include/xen/ doesn't imply arbitrary
>>>>>>>> restrictions on acceptable values.
>>>>>>> Well yes the code is simple. However, the code as it is wouldn't be
>>>>>>> usuable on other architecture without additional work (aside arch
>>>>>>> specific code). For instance, there is no way to map the buffer outside
>>>>>>> of Xen as it is all x86 specific.
>>>>>>>
>>>>>>> If you want the allocation to be in the common code, then the
>>>>>>> infrastructure to map/unmap the buffer should also be in common code.
>>>>>>> Otherwise, there is no point to allocate it in common.
>>>>>>
>>>>>> I don't think I agree here - I see nothing wrong with exposing of
>>>>>> the memory being arch specific, when allocation is generic. This
>>>>>> is no different from, in just x86, allocation logic being common
>>>>>> to PV and HVM, but exposing being different for both.
>>>>>
>>>>> Are you suggesting that the way it would be exposed may be different for
>>>>> other architecture?
>>>>
>>>> Why not? To take a possibly extreme example - consider an arch
>>>> where (for bare metal) the buffer is specified to appear at a
>>>> fixed range of addresses.
>>>
>>> I am probably missing something here... The current goal is the buffer
>>> will be mapped in the dom0. Most likely the way to map it will be using
>>> the acquire hypercall (unless you invent a brand new one...).
>>>
>>> For a guest, you could possibly reserve a fixed range and then map it
>>> when creating the vCPU in Xen. But then, you will likely want a fixed
>>> size... So why would you bother to ask the user to define the size?
>>
>> Because there may be the option to only populate part of the fixed
>> range?
>
> It was yet another extreme case ;).
Yes, sure - just to demonstrate my point.
>>> Another way to do it, would be the toolstack to do the mapping. At which
>>> point, you still need an hypercall to do the mapping (probably the
>>> hypercall acquire).
>>
>> There may not be any mapping to do in such a contrived, fixed-range
>> environment. This scenario was specifically to demonstrate that the
>> way the mapping gets done may be arch-specific (here: a no-op)
>> despite the allocation not being so.
> You are arguing on extreme cases which I don't think is really helpful
> here. Yes if you want to map at a fixed address in a guest you may not
> need the acquire hypercall. But in most of the other cases (see has for
> the tools) you will need it.
>
> So what's the problem with requesting to have the acquire hypercall
> implemented in common code?
Didn't we start out by you asking that there be as little common code
as possible for the time being? I have no issue with putting the
acquire implementation there ...
Jan
next prev parent reply other threads:[~2020-07-02 14:17 UTC|newest]
Thread overview: 75+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-30 12:33 [PATCH v4 00/10] Implement support for external IPT monitoring Michał Leszczyński
2020-06-30 12:33 ` [PATCH v4 01/10] x86/vmx: add Intel PT MSR definitions Michał Leszczyński
2020-06-30 16:23 ` Jan Beulich
2020-06-30 17:37 ` Andrew Cooper
2020-06-30 18:03 ` Tamas K Lengyel
2020-06-30 18:27 ` Michał Leszczyński
2020-07-01 17:52 ` Andrew Cooper
2020-06-30 12:33 ` [PATCH v4 02/10] x86/vmx: add IPT cpu feature Michał Leszczyński
2020-07-01 9:49 ` Roger Pau Monné
2020-07-01 15:12 ` Julien Grall
2020-07-01 16:06 ` Andrew Cooper
2020-07-01 16:17 ` Julien Grall
2020-07-01 16:18 ` Julien Grall
2020-07-01 17:26 ` Andrew Cooper
2020-07-01 18:02 ` Julien Grall
2020-07-01 18:06 ` Andrew Cooper
2020-07-01 18:09 ` Julien Grall
2020-07-02 8:29 ` Jan Beulich
2020-07-02 8:42 ` Julien Grall
2020-07-02 8:50 ` Jan Beulich
2020-07-02 8:54 ` Julien Grall
2020-07-02 9:18 ` Jan Beulich
2020-07-02 9:57 ` Julien Grall
2020-07-02 13:30 ` Jan Beulich
2020-07-02 14:14 ` Julien Grall
2020-07-02 14:17 ` Jan Beulich [this message]
2020-07-02 14:31 ` Julien Grall
2020-07-02 20:28 ` Michał Leszczyński
2020-07-03 7:58 ` Julien Grall
2020-07-04 19:16 ` Michał Leszczyński
2020-07-01 21:42 ` Andrew Cooper
2020-07-02 8:10 ` Roger Pau Monné
2020-07-02 8:34 ` Jan Beulich
2020-07-02 20:29 ` Michał Leszczyński
2020-06-30 12:33 ` [PATCH v4 03/10] tools/libxl: add vmtrace_pt_size parameter Michał Leszczyński
2020-07-01 10:05 ` Roger Pau Monné
2020-07-02 9:00 ` Roger Pau Monné
2020-07-02 16:23 ` Michał Leszczyński
2020-07-03 9:44 ` Roger Pau Monné
2020-07-03 9:56 ` Jan Beulich
2020-07-03 10:11 ` Roger Pau Monné
2020-07-04 17:23 ` Julien Grall
2020-07-06 8:46 ` Jan Beulich
2020-07-07 8:44 ` Julien Grall
2020-07-07 9:10 ` Jan Beulich
2020-07-07 9:16 ` Julien Grall
2020-07-07 11:17 ` Michał Leszczyński
2020-07-07 11:21 ` Jan Beulich
2020-07-07 11:35 ` Michał Leszczyński
2020-07-02 10:24 ` Anthony PERARD
2020-07-04 17:48 ` Julien Grall
2020-06-30 12:33 ` [PATCH v4 04/10] x86/vmx: implement processor tracing for VMX Michał Leszczyński
2020-07-01 10:30 ` Roger Pau Monné
2020-06-30 12:33 ` [PATCH v4 05/10] common/domain: allocate vmtrace_pt_buffer Michał Leszczyński
2020-07-01 10:38 ` Roger Pau Monné
2020-07-01 15:35 ` Julien Grall
2020-06-30 12:33 ` [PATCH v4 06/10] memory: batch processing in acquire_resource() Michał Leszczyński
2020-07-01 10:46 ` Roger Pau Monné
2020-07-03 10:35 ` Julien Grall
2020-07-03 10:52 ` Paul Durrant
2020-07-03 11:17 ` Julien Grall
2020-07-03 11:22 ` Jan Beulich
2020-07-03 11:36 ` Julien Grall
2020-07-03 12:50 ` Jan Beulich
2020-07-03 11:40 ` Paul Durrant
2020-06-30 12:33 ` [PATCH v4 07/10] x86/mm: add vmtrace_buf resource type Michał Leszczyński
2020-07-01 10:52 ` Roger Pau Monné
2020-06-30 12:33 ` [PATCH v4 08/10] x86/domctl: add XEN_DOMCTL_vmtrace_op Michał Leszczyński
2020-07-01 11:00 ` Roger Pau Monné
2020-06-30 12:33 ` [PATCH v4 09/10] tools/libxc: add xc_vmtrace_* functions Michał Leszczyński
2020-07-21 10:52 ` Wei Liu
2020-06-30 12:33 ` [PATCH v4 10/10] tools/proctrace: add proctrace tool Michał Leszczyński
2020-07-02 15:10 ` Andrew Cooper
2020-07-21 10:52 ` Wei Liu
2020-06-30 12:48 ` [PATCH v4 00/10] Implement support for external IPT monitoring Hubert Jasudowicz
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