From: Jan Beulich <jbeulich@suse.com>
To: "Bertrand Marquis" <Bertrand.Marquis@arm.com>,
"Roger Pau Monné" <roger.pau@citrix.com>
Cc: Ian Jackson <iwj@xenproject.org>, Paul Durrant <paul@xen.org>,
Andrew Cooper <andrew.cooper3@citrix.com>, Wei Liu <wl@xen.org>,
"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
Julien Grall <julien@xen.org>
Subject: Re: [PATCH v6 1/3] xen/vpci: Move ecam access functions to common code
Date: Fri, 15 Oct 2021 10:13:24 +0200 [thread overview]
Message-ID: <9f0f8e0b-c989-d2ae-39eb-6784446fa6c3@suse.com> (raw)
In-Reply-To: <152124C4-9A34-4F5B-B6C5-CBCC6A175665@arm.com>
On 15.10.2021 09:37, Bertrand Marquis wrote:
>> On 15 Oct 2021, at 07:29, Jan Beulich <jbeulich@suse.com> wrote:
>> On 14.10.2021 19:09, Bertrand Marquis wrote:
>>>> On 14 Oct 2021, at 17:06, Jan Beulich <jbeulich@suse.com> wrote:
>>>> On 14.10.2021 16:49, Bertrand Marquis wrote:
>>>>> @@ -305,7 +291,7 @@ static int vpci_portio_read(const struct hvm_io_handler *handler,
>>>>>
>>>>> reg = hvm_pci_decode_addr(cf8, addr, &sbdf);
>>>>>
>>>>> - if ( !vpci_access_allowed(reg, size) )
>>>>> + if ( !vpci_ecam_access_allowed(reg, size) )
>>>>> return X86EMUL_OKAY;
>>>>>
>>>>> *data = vpci_read(sbdf, reg, size);
>>>>> @@ -335,7 +321,7 @@ static int vpci_portio_write(const struct hvm_io_handler *handler,
>>>>>
>>>>> reg = hvm_pci_decode_addr(cf8, addr, &sbdf);
>>>>>
>>>>> - if ( !vpci_access_allowed(reg, size) )
>>>>> + if ( !vpci_ecam_access_allowed(reg, size) )
>>>>> return X86EMUL_OKAY;
>>>>>
>>>>> vpci_write(sbdf, reg, size, data);
>>>>
>>>> Why would port I/O functions call an ECAM helper? And in how far is
>>>> that helper actually ECAM-specific?
>>>
>>> The function was global before.
>>
>> I'm not objecting to the function being global, but to the "ecam" in
>> its name.
>
> Adding ecam in the name was a request from Roger.
> This is just a consequence of this.
Roger - did you have in mind the uses here when asking for the addition
of "ecam"?
> One suggestion here could be to turn vpci_ecam_access_allowed into
> vpci_access_allowed
That's what I'm asking for.
> and maybe put this into vpci.h as a static inline ?
I'm not overly fussed here.
>>>>> @@ -434,25 +420,8 @@ static int vpci_mmcfg_read(struct vcpu *v, unsigned long addr,
>>>>> reg = vpci_mmcfg_decode_addr(mmcfg, addr, &sbdf);
>>>>> read_unlock(&d->arch.hvm.mmcfg_lock);
>>>>>
>>>>> - if ( !vpci_access_allowed(reg, len) ||
>>>>> - (reg + len) > PCI_CFG_SPACE_EXP_SIZE )
>>>>> - return X86EMUL_OKAY;
>>>>
>>>> While I assume this earlier behavior is the reason for ...
>>>
>>> Yes :-)
>>>
>>>>
>>>>> - /*
>>>>> - * According to the PCIe 3.1A specification:
>>>>> - * - Configuration Reads and Writes must usually be DWORD or smaller
>>>>> - * in size.
>>>>> - * - Because Root Complex implementations are not required to support
>>>>> - * accesses to a RCRB that cross DW boundaries [...] software
>>>>> - * should take care not to cause the generation of such accesses
>>>>> - * when accessing a RCRB unless the Root Complex will support the
>>>>> - * access.
>>>>> - * Xen however supports 8byte accesses by splitting them into two
>>>>> - * 4byte accesses.
>>>>> - */
>>>>> - *data = vpci_read(sbdf, reg, min(4u, len));
>>>>> - if ( len == 8 )
>>>>> - *data |= (uint64_t)vpci_read(sbdf, reg + 4, 4) << 32;
>>>>> + /* Ignore return code */
>>>>> + vpci_ecam_mmio_read(sbdf, reg, len, data);
>>>>
>>>> ... the commented-upon ignoring of the return value, I don't think
>>>> that's a good way to deal with things anymore. Instead I think
>>>> *data should be written to ~0 upon failure, unless it is intended
>>>> for vpci_ecam_mmio_read() to take care of that case (in which case
>>>> I'm not sure I would see why it needs to return an error indicator
>>>> in the first place).
>>>
>>> I am not sure in the first place why this is actually ignored and just
>>> returning a -1 value.
>>> If an access is not right, an exception should be generated to the
>>> Guest instead.
>>
>> No. That's also not what happens on bare metal, at least not on x86.
>> Faults cannot be raised for reasons outside of the CPU; such errors
>> (if these are errors in the first place) need to be dealt with
>> differently. Signaling an error on the PCI bus would be possible,
>> but would leave open how that's actually to be dealt with. Instead
>> bad reads return all ones, while bad writes simply get dropped.
>
> So that behaviour is kept here on x86 and I think as the function is
> generic it is right for it to return an error here. It is up to the caller to
> ignore it or not.
> To make this more generic I could return 0 on success and -EACCESS,
> the caller would then handle it as he wants.
I think boolean is sufficient here, but I wouldn't object to errno-
style return values. All I do object to is int when boolean is meant.
>>>>> +int vpci_ecam_mmio_write(pci_sbdf_t sbdf, unsigned int reg, unsigned int len,
>>>>> + unsigned long data)
>>>>> +{
>>>>> + if ( !vpci_ecam_access_allowed(reg, len) ||
>>>>> + (reg + len) > PCI_CFG_SPACE_EXP_SIZE )
>>>>> + return 0;
>>>>> +
>>>>> + vpci_write(sbdf, reg, min(4u, len), data);
>>>>> + if ( len == 8 )
>>>>> + vpci_write(sbdf, reg + 4, 4, data >> 32);
>>>>> +
>>>>> + return 1;
>>>>> +}
>>>>> +
>>>>> +int vpci_ecam_mmio_read(pci_sbdf_t sbdf, unsigned int reg, unsigned int len,
>>>>> + unsigned long *data)
>>>>> +{
>>>>> + if ( !vpci_ecam_access_allowed(reg, len) ||
>>>>> + (reg + len) > PCI_CFG_SPACE_EXP_SIZE )
>>>>> + return 0;
>>>>> +
>>>>> + /*
>>>>> + * According to the PCIe 3.1A specification:
>>>>> + * - Configuration Reads and Writes must usually be DWORD or smaller
>>>>> + * in size.
>>>>> + * - Because Root Complex implementations are not required to support
>>>>> + * accesses to a RCRB that cross DW boundaries [...] software
>>>>> + * should take care not to cause the generation of such accesses
>>>>> + * when accessing a RCRB unless the Root Complex will support the
>>>>> + * access.
>>>>> + * Xen however supports 8byte accesses by splitting them into two
>>>>> + * 4byte accesses.
>>>>> + */
>>>>> + *data = vpci_read(sbdf, reg, min(4u, len));
>>>>> + if ( len == 8 )
>>>>> + *data |= (uint64_t)vpci_read(sbdf, reg + 4, 4) << 32;
>>>>> +
>>>>> + return 1;
>>>>> +}
>>>>
>>>> Why do these two functions return int/0/1 instead of
>>>> bool/false/true (assuming, as per above, that them returning non-
>>>> void is warranted at all)?
>>>
>>> This is what the mmio handlers should return to say that an access
>>> was ok or not so the function stick to this standard.
>>
>> Sticking to this would be okay if the functions here needed their
>> address taken, such that they can be installed as hooks for a
>> more general framework to invoke. The functions, however, only get
>> called directly. Hence there's no reason to mirror what is in need
>> of cleaning up elsewhere. I'm sure you're aware there we're in the
>> (slow going) process of improving which types get used where.
>> While the functions you refer to may not have undergone such
>> cleanup yet, we generally expect new code to conform to the new
>> model.
>
> I am ok to rename those to vpci_ecam_{read/write}.
> Is it what you want ?
Yes, that's what I've been asking for, and I just saw Roger requesting
the same. (I'm a little puzzled about the context though, as you reply
looks disconnected here.)
Jan
next prev parent reply other threads:[~2021-10-15 8:13 UTC|newest]
Thread overview: 190+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-06 17:40 [PATCH v5 00/11] PCI devices passthrough on Arm Rahul Singh
2021-10-06 17:40 ` [PATCH v5 01/11] xen/arm: xc_domain_ioport_permission(..) not supported on ARM Rahul Singh
2021-10-11 11:47 ` Roger Pau Monné
2021-10-11 12:11 ` Bertrand Marquis
2021-10-11 13:20 ` Roger Pau Monné
2021-10-11 13:40 ` Bertrand Marquis
2021-10-11 13:57 ` Roger Pau Monné
2021-10-11 14:16 ` Bertrand Marquis
2021-10-11 16:32 ` Roger Pau Monné
2021-10-11 17:11 ` Bertrand Marquis
2021-10-12 8:29 ` Jan Beulich
2021-10-12 8:41 ` Bertrand Marquis
2021-10-12 9:32 ` Jan Beulich
2021-10-12 9:38 ` Oleksandr Andrushchenko
2021-10-12 10:01 ` Jan Beulich
2021-10-12 10:06 ` Oleksandr Andrushchenko
2021-10-12 10:20 ` Jan Beulich
2021-10-12 10:41 ` Bertrand Marquis
2021-10-12 10:44 ` Jan Beulich
2021-10-12 14:53 ` Ian Jackson
2021-10-12 16:15 ` Bertrand Marquis
2021-10-12 16:29 ` Ian Jackson
2021-10-12 20:42 ` Stefano Stabellini
2021-10-13 8:07 ` Roger Pau Monné
2021-10-13 11:52 ` Ian Jackson
2021-10-13 8:02 ` Roger Pau Monné
2021-10-13 12:02 ` Ian Jackson
2021-10-12 9:40 ` Bertrand Marquis
2021-10-12 10:03 ` Jan Beulich
2021-10-11 14:16 ` Oleksandr Andrushchenko
2021-10-06 17:40 ` [PATCH v5 02/11] xen/arm: Add PHYSDEVOP_pci_device_(*add/remove) support for ARM Rahul Singh
2021-10-07 0:05 ` Stefano Stabellini
2021-10-07 12:58 ` Jan Beulich
2021-10-21 9:28 ` xen/arm: Missing appropriate locking for the IOMMU (WAS Re: [PATCH v5 02/11] xen/arm: Add PHYSDEVOP_pci_device_(*add/remove) support for ARM) Julien Grall
2021-10-21 13:15 ` Bertrand Marquis
2021-10-21 13:47 ` Julien Grall
2021-10-21 13:52 ` Bertrand Marquis
2021-10-06 17:40 ` [PATCH v5 03/11] xen/arm: Add cmdline boot option "pci-passthrough = <boolean>" Rahul Singh
2021-10-07 8:27 ` Jan Beulich
2021-10-07 8:32 ` Rahul Singh
2021-10-07 12:59 ` Jan Beulich
2021-10-06 17:40 ` [PATCH v5 04/11] xen/arm: PCI host bridge discovery within XEN on ARM Rahul Singh
2021-10-06 17:40 ` [PATCH v5 05/11] xen/arm: Add support for Xilinx ZynqMP PCI host controller Rahul Singh
2021-10-06 17:40 ` [PATCH v5 06/11] xen/arm: Implement pci access functions Rahul Singh
2021-10-06 17:40 ` [PATCH v5 07/11] xen/domctl: Introduce XEN_DOMCTL_CDF_vpci flag Rahul Singh
2021-10-07 13:08 ` Jan Beulich
2021-10-08 18:06 ` Andrew Cooper
2021-10-08 21:12 ` Julien Grall
2021-10-08 21:46 ` Stefano Stabellini
2021-10-11 9:24 ` Julien Grall
2021-10-11 11:29 ` Michal Orzel
2021-10-11 11:35 ` Jan Beulich
2021-10-11 13:17 ` Roger Pau Monné
2021-10-11 9:48 ` Ian Jackson
2021-10-11 9:27 ` Roger Pau Monné
2021-10-11 12:06 ` Michal Orzel
2021-10-12 10:38 ` Michal Orzel
2021-10-13 8:30 ` Roger Pau Monné
2021-10-13 9:36 ` Bertrand Marquis
2021-10-13 10:56 ` Roger Pau Monné
2021-10-13 12:11 ` Bertrand Marquis
2021-10-13 12:57 ` Jan Beulich
2021-10-13 20:41 ` Stefano Stabellini
2021-10-14 6:23 ` Jan Beulich
2021-10-14 7:53 ` Bertrand Marquis
2021-10-13 14:28 ` Roger Pau Monné
2021-10-13 20:53 ` Stefano Stabellini
2021-10-13 23:21 ` Stefano Stabellini
2021-10-12 21:48 ` Stefano Stabellini
2021-10-13 6:18 ` Jan Beulich
2021-10-13 7:11 ` Michal Orzel
2021-10-06 17:40 ` [PATCH v5 08/11] xen/arm: Enable the existing x86 virtual PCI support for ARM Rahul Singh
2021-10-07 13:43 ` Jan Beulich
2021-10-11 12:41 ` Bertrand Marquis
2021-10-11 13:09 ` Jan Beulich
2021-10-11 13:34 ` Bertrand Marquis
2021-10-11 14:10 ` Jan Beulich
2021-10-11 14:52 ` Bertrand Marquis
2021-10-11 18:18 ` Stefano Stabellini
2021-10-12 8:04 ` Jan Beulich
2021-10-12 21:37 ` Stefano Stabellini
2021-10-13 6:10 ` Jan Beulich
2021-10-13 10:02 ` Bertrand Marquis
2021-10-13 12:21 ` Jan Beulich
2021-10-12 15:04 ` Julien Grall
2021-10-12 16:12 ` Bertrand Marquis
2021-10-12 16:20 ` Julien Grall
2021-10-12 17:50 ` Bertrand Marquis
2021-10-11 10:51 ` Roger Pau Monné
2021-10-11 16:12 ` Bertrand Marquis
2021-10-11 16:20 ` Oleksandr Andrushchenko
2021-10-11 16:43 ` Roger Pau Monné
2021-10-11 17:15 ` Bertrand Marquis
2021-10-11 18:30 ` Oleksandr Andrushchenko
2021-10-11 19:27 ` Stefano Stabellini
2021-10-12 5:34 ` Oleksandr Andrushchenko
2021-10-12 7:44 ` Bertrand Marquis
2021-10-12 14:32 ` Julien Grall
2021-10-12 14:34 ` Bertrand Marquis
2021-10-13 8:45 ` Roger Pau Monné
2021-10-13 9:48 ` Bertrand Marquis
2021-10-13 10:33 ` Roger Pau Monné
2021-10-13 13:00 ` Jan Beulich
2021-10-13 14:51 ` Oleksandr Andrushchenko
2021-10-13 15:15 ` Jan Beulich
2021-10-13 19:27 ` Stefano Stabellini
2021-10-14 6:33 ` Jan Beulich
2021-10-14 7:53 ` Bertrand Marquis
2021-10-14 9:03 ` Bertrand Marquis
2021-10-14 9:24 ` Jan Beulich
2021-10-06 17:40 ` [PATCH v5 09/11] xen/arm: Transitional change to build HAS_VPCI on ARM Rahul Singh
2021-10-11 11:43 ` Roger Pau Monné
2021-10-11 12:15 ` Bertrand Marquis
2021-10-12 1:32 ` Stefano Stabellini
2021-10-06 17:40 ` [PATCH v5 10/11] arm/libxl: Emulated PCI device tree node in libxl Rahul Singh
2021-10-06 18:01 ` Julien Grall
2021-10-07 0:26 ` Stefano Stabellini
2021-10-07 15:31 ` Rahul Singh
2021-10-07 10:53 ` Ian Jackson
2021-10-07 15:29 ` Rahul Singh
2021-10-07 16:11 ` Ian Jackson
2021-10-11 13:46 ` Roger Pau Monné
2021-10-14 17:16 ` Bertrand Marquis
2021-10-14 14:49 ` [PATCH v6 0/3] PCI devices passthrough on Arm Bertrand Marquis
2021-10-14 14:49 ` [PATCH v6 1/3] xen/vpci: Move ecam access functions to common code Bertrand Marquis
2021-10-14 16:06 ` Jan Beulich
2021-10-14 17:09 ` Bertrand Marquis
2021-10-15 6:29 ` Jan Beulich
2021-10-15 7:37 ` Bertrand Marquis
2021-10-15 8:13 ` Jan Beulich [this message]
2021-10-15 8:20 ` Bertrand Marquis
2021-10-15 8:24 ` Jan Beulich
2021-10-15 9:49 ` Roger Pau Monné
2021-10-14 23:47 ` Stefano Stabellini
2021-10-15 7:44 ` Roger Pau Monné
2021-10-15 7:53 ` Bertrand Marquis
2021-10-15 9:53 ` Roger Pau Monné
2021-10-15 10:12 ` Bertrand Marquis
2021-10-15 10:14 ` Jan Beulich
2021-10-14 14:49 ` [PATCH v6 2/3] xen/arm: Enable the existing x86 virtual PCI support for ARM Bertrand Marquis
2021-10-14 23:49 ` Stefano Stabellini
2021-10-15 6:40 ` Jan Beulich
2021-10-15 9:59 ` Ian Jackson
2021-10-15 10:10 ` Bertrand Marquis
2021-10-15 8:00 ` Jan Beulich
2021-10-15 10:09 ` Bertrand Marquis
2021-10-15 10:14 ` Ian Jackson
2021-10-15 10:18 ` Jan Beulich
2021-10-15 11:35 ` Roger Pau Monné
2021-10-15 12:13 ` Bertrand Marquis
2021-10-15 12:18 ` Jan Beulich
2021-10-15 12:28 ` Bertrand Marquis
2021-10-15 13:00 ` Jan Beulich
2021-10-15 13:10 ` Bertrand Marquis
2021-10-15 10:38 ` Jan Beulich
2021-10-15 8:32 ` Roger Pau Monné
2021-10-15 8:42 ` Michal Orzel
2021-10-15 9:52 ` Bertrand Marquis
2021-10-15 10:13 ` Luca Fancellu
2021-10-15 10:17 ` Bertrand Marquis
2021-10-15 10:19 ` Roger Pau Monné
2021-10-15 10:31 ` Bertrand Marquis
2021-10-15 10:24 ` Jan Beulich
2021-10-15 10:33 ` Bertrand Marquis
2021-10-15 10:41 ` Jan Beulich
2021-10-15 10:48 ` Bertrand Marquis
2021-10-15 10:51 ` Jan Beulich
2021-10-15 11:08 ` Bertrand Marquis
2021-10-15 13:47 ` Roger Pau Monné
2021-10-15 14:00 ` Luca Fancellu
2021-10-15 14:32 ` Roger Pau Monné
2021-10-14 14:49 ` [PATCH v6 3/3] arm/libxl: Emulated PCI device tree node in libxl Bertrand Marquis
2021-10-14 17:54 ` [PATCH v6 3/3] arm/libxl: Emulated PCI device tree node in libxl [and 1 more messages] Ian Jackson
2021-10-14 23:50 ` Stefano Stabellini
2021-10-15 7:28 ` Julien Grall
2021-10-15 7:41 ` Michal Orzel
2021-10-15 9:01 ` Julien Grall
2021-10-15 10:02 ` Ian Jackson
2021-10-15 10:58 ` Michal Orzel
2021-10-15 11:04 ` Michal Orzel
2021-10-15 11:46 ` Ian Jackson
2021-10-15 11:53 ` Michal Orzel
2021-10-15 12:10 ` Julien Grall
2021-10-15 12:14 ` Ian Jackson
2021-10-15 12:13 ` Ian Jackson
2021-10-12 15:03 ` [PATCH v5 10/11] arm/libxl: Emulated PCI device tree node in libxl Ian Jackson
2021-10-06 17:40 ` [PATCH v5 11/11] xen/arm: Add linux,pci-domain property for hwdom if not available Rahul Singh
2021-10-13 20:54 ` Stefano Stabellini
2021-10-07 19:54 ` [PATCH v5 00/11] PCI devices passthrough on Arm Stefano Stabellini
2021-10-07 21:29 ` Rahul Singh
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