From: Julien Grall <julien@xen.org>
To: Jan Beulich <jbeulich@suse.com>, Oleksandr <olekstysh@gmail.com>
Cc: "xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
Oleksandr Tyshchenko <Oleksandr_Tyshchenko@epam.com>,
Stefano Stabellini <sstabellini@kernel.org>,
Julien Grall <julien.grall@arm.com>,
Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
Subject: Re: [PATCH V3 19/23] xen/arm: io: Abstract sign-extension
Date: Tue, 1 Dec 2020 10:30:43 +0000 [thread overview]
Message-ID: <d7b8f43d-2a59-6316-5609-0595b2a86045@xen.org> (raw)
In-Reply-To: <93284ea1-e658-ffff-3223-174d633e38ad@suse.com>
Hi Jan,
On 01/12/2020 07:55, Jan Beulich wrote:
> On 01.12.2020 00:27, Oleksandr wrote:
>> On 30.11.20 23:03, Volodymyr Babchuk wrote:
>>> Oleksandr Tyshchenko writes:
>>>> --- a/xen/include/asm-arm/traps.h
>>>> +++ b/xen/include/asm-arm/traps.h
>>>> @@ -83,6 +83,30 @@ static inline bool VABORT_GEN_BY_GUEST(const struct cpu_user_regs *regs)
>>>> (unsigned long)abort_guest_exit_end == regs->pc;
>>>> }
>>>>
>>>> +/* Check whether the sign extension is required and perform it */
>>>> +static inline register_t sign_extend(const struct hsr_dabt dabt, register_t r)
>>>> +{
>>>> + uint8_t size = (1 << dabt.size) * 8;
>>>> +
>>>> + /*
>>>> + * Sign extend if required.
>>>> + * Note that we expect the read handler to have zeroed the bits
>>>> + * outside the requested access size.
>>>> + */
>>>> + if ( dabt.sign && (r & (1UL << (size - 1))) )
>>>> + {
>>>> + /*
>>>> + * We are relying on register_t using the same as
>>>> + * an unsigned long in order to keep the 32-bit assembly
>>>> + * code smaller.
>>>> + */
>>>> + BUILD_BUG_ON(sizeof(register_t) != sizeof(unsigned long));
>>>> + r |= (~0UL) << size;
>>> If `size` is 64, you will get undefined behavior there.
>> I think, we don't need to worry about undefined behavior here. Having
>> size=64 would be possible with doubleword (dabt.size=3). But if "r"
>> adjustment gets called (I mean Syndrome Sign Extend bit is set) then
>> we deal with byte, halfword or word operations (dabt.size<3). Or I
>> missed something?
>
> At which point please put in a respective ASSERT(), possibly amended
> by a brief comment.
ASSERT()s are only meant to catch programatic error. However, in this
case, the bigger risk is an hardware bug such as advertising a sign
extension for either 64-bit (or 32-bit) on Arm64 (resp. Arm32).
Actually the Armv8 spec is a bit more blurry when running in AArch32
state because they suggest that the sign extension can be set even for
32-bit access. I think this is a spelling mistake, but it is probably
better to be cautious here.
Therefore, I would recommend to rework the code so it is only called
when len < sizeof(register_t).
Cheers,
--
Julien Grall
next prev parent reply other threads:[~2020-12-01 10:31 UTC|newest]
Thread overview: 127+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-30 10:31 Oleksandr Tyshchenko
2020-11-30 10:31 ` [PATCH V3 01/23] x86/ioreq: Prepare IOREQ feature for making it common Oleksandr Tyshchenko
2020-12-01 11:03 ` Alex Bennée
2020-12-01 18:53 ` Oleksandr
2020-12-01 19:36 ` Alex Bennée
2020-12-02 8:00 ` Jan Beulich
2020-12-02 11:19 ` Oleksandr
2020-12-07 11:13 ` Jan Beulich
2020-12-07 15:27 ` Oleksandr
2020-12-07 16:29 ` Jan Beulich
2020-12-07 17:21 ` Oleksandr
2020-11-30 10:31 ` [PATCH V3 02/23] x86/ioreq: Add IOREQ_STATUS_* #define-s and update code for moving Oleksandr Tyshchenko
2020-12-01 11:07 ` Alex Bennée
2020-12-07 11:19 ` Jan Beulich
2020-12-07 15:37 ` Oleksandr
2020-11-30 10:31 ` [PATCH V3 03/23] x86/ioreq: Provide out-of-line wrapper for the handle_mmio() Oleksandr Tyshchenko
2020-12-07 11:27 ` Jan Beulich
2020-12-07 15:39 ` Oleksandr
2020-11-30 10:31 ` [PATCH V3 04/23] xen/ioreq: Make x86's IOREQ feature common Oleksandr Tyshchenko
2020-12-07 11:41 ` Jan Beulich
2020-12-07 19:43 ` Oleksandr
2020-12-08 9:21 ` Jan Beulich
2020-12-08 13:56 ` Oleksandr
2020-12-08 15:02 ` Jan Beulich
2020-12-08 17:24 ` Oleksandr
2020-11-30 10:31 ` [PATCH V3 05/23] xen/ioreq: Make x86's hvm_ioreq_needs_completion() common Oleksandr Tyshchenko
2020-12-07 11:47 ` Jan Beulich
2020-11-30 10:31 ` [PATCH V3 06/23] xen/ioreq: Make x86's hvm_mmio_first(last)_byte() common Oleksandr Tyshchenko
2020-12-07 11:48 ` Jan Beulich
2020-11-30 10:31 ` [PATCH V3 07/23] xen/ioreq: Make x86's hvm_ioreq_(page/vcpu/server) structs common Oleksandr Tyshchenko
2020-12-07 11:54 ` Jan Beulich
2020-11-30 10:31 ` [PATCH V3 08/23] xen/ioreq: Move x86's ioreq_server to struct domain Oleksandr Tyshchenko
2020-12-07 12:04 ` Jan Beulich
2020-12-07 12:12 ` Paul Durrant
2020-12-07 19:52 ` Oleksandr
2020-11-30 10:31 ` [PATCH V3 09/23] xen/dm: Make x86's DM feature common Oleksandr Tyshchenko
2020-12-07 12:08 ` Jan Beulich
2020-12-07 20:23 ` Oleksandr
2020-12-08 9:30 ` Jan Beulich
2020-12-08 14:54 ` Oleksandr
2021-01-07 14:38 ` Oleksandr
2021-01-07 15:01 ` Jan Beulich
2021-01-07 16:49 ` Oleksandr
2021-01-12 22:23 ` Oleksandr
2020-11-30 10:31 ` [PATCH V3 10/23] xen/mm: Make x86's XENMEM_resource_ioreq_server handling common Oleksandr Tyshchenko
2020-12-07 11:35 ` Jan Beulich
2020-12-07 12:11 ` Jan Beulich
2020-12-07 21:06 ` Oleksandr
2020-11-30 10:31 ` [PATCH V3 11/23] xen/ioreq: Move x86's io_completion/io_req fields to struct vcpu Oleksandr Tyshchenko
2020-12-07 12:32 ` Jan Beulich
2020-12-07 20:59 ` Oleksandr
2020-12-08 7:52 ` Paul Durrant
2020-12-08 9:35 ` Jan Beulich
2020-12-08 18:21 ` Oleksandr
2020-11-30 10:31 ` [PATCH V3 12/23] xen/ioreq: Remove "hvm" prefixes from involved function names Oleksandr Tyshchenko
2020-12-07 12:45 ` Jan Beulich
2020-12-07 20:28 ` Oleksandr
2020-11-30 10:31 ` [PATCH V3 13/23] xen/ioreq: Use guest_cmpxchg64() instead of cmpxchg() Oleksandr Tyshchenko
2020-12-09 21:32 ` Stefano Stabellini
2020-12-09 22:34 ` Oleksandr
2020-12-10 2:30 ` Stefano Stabellini
2020-11-30 10:31 ` [PATCH V3 14/23] arm/ioreq: Introduce arch specific bits for IOREQ/DM features Oleksandr Tyshchenko
2020-12-09 22:04 ` Stefano Stabellini
2020-12-09 22:49 ` Oleksandr
2020-12-10 2:30 ` Stefano Stabellini
2020-11-30 10:31 ` [PATCH V3 15/23] xen/arm: Stick around in leave_hypervisor_to_guest until I/O has completed Oleksandr Tyshchenko
2020-11-30 20:51 ` Volodymyr Babchuk
2020-12-01 12:46 ` Julien Grall
2020-12-09 23:18 ` Stefano Stabellini
2020-12-09 23:35 ` Stefano Stabellini
2020-12-09 23:47 ` Julien Grall
2020-12-10 2:30 ` Stefano Stabellini
2020-12-10 13:17 ` Julien Grall
2020-12-10 13:21 ` Oleksandr
2020-12-09 23:38 ` Julien Grall
2020-11-30 10:31 ` [PATCH V3 16/23] xen/mm: Handle properly reference in set_foreign_p2m_entry() on Arm Oleksandr Tyshchenko
2020-12-08 14:24 ` Jan Beulich
2020-12-08 16:41 ` Oleksandr
2020-12-09 23:49 ` Stefano Stabellini
2021-01-15 1:18 ` Stefano Stabellini
2020-11-30 10:31 ` [PATCH V3 17/23] xen/ioreq: Introduce domain_has_ioreq_server() Oleksandr Tyshchenko
2020-12-08 15:11 ` Jan Beulich
2020-12-08 15:33 ` Oleksandr
2020-12-08 16:56 ` Oleksandr
2020-12-08 19:43 ` Paul Durrant
2020-12-08 20:16 ` Oleksandr
2020-12-09 9:01 ` Paul Durrant
2020-12-09 18:58 ` Julien Grall
2020-12-09 21:05 ` Oleksandr
2020-12-09 20:36 ` Oleksandr
2020-12-10 8:38 ` Paul Durrant
2020-12-10 16:57 ` Oleksandr
2020-11-30 10:31 ` [PATCH V3 18/23] xen/dm: Introduce xendevicemodel_set_irq_level DM op Oleksandr Tyshchenko
2020-12-10 2:21 ` Stefano Stabellini
2020-12-10 12:58 ` Oleksandr
2020-12-10 13:38 ` Julien Grall
2020-11-30 10:31 ` [PATCH V3 19/23] xen/arm: io: Abstract sign-extension Oleksandr Tyshchenko
2020-11-30 21:03 ` Volodymyr Babchuk
2020-11-30 23:27 ` Oleksandr
2020-12-01 7:55 ` Jan Beulich
2020-12-01 10:30 ` Julien Grall [this message]
2020-12-01 10:42 ` Oleksandr
2020-12-01 12:13 ` Julien Grall
2020-12-01 12:24 ` Oleksandr
2020-12-01 12:28 ` Julien Grall
2020-12-01 10:49 ` Jan Beulich
2020-12-01 10:23 ` Julien Grall
2020-11-30 10:31 ` [PATCH V3 20/23] xen/ioreq: Make x86's send_invalidate_req() common Oleksandr Tyshchenko
2020-12-08 15:24 ` Jan Beulich
2020-12-08 16:49 ` Oleksandr
2020-12-09 8:21 ` Jan Beulich
2020-11-30 10:31 ` [PATCH V3 21/23] xen/arm: Add mapcache invalidation handling Oleksandr Tyshchenko
2020-12-10 2:30 ` Stefano Stabellini
2020-12-10 18:50 ` Julien Grall
2020-12-11 1:28 ` Stefano Stabellini
2020-12-11 11:21 ` Oleksandr
2020-12-11 19:07 ` Stefano Stabellini
2020-12-11 19:37 ` Julien Grall
2020-12-11 19:27 ` Julien Grall
2020-11-30 10:31 ` [PATCH V3 22/23] libxl: Introduce basic virtio-mmio support on Arm Oleksandr Tyshchenko
2020-11-30 10:31 ` [PATCH V3 23/23] [RFC] libxl: Add support for virtio-disk configuration Oleksandr Tyshchenko
2020-11-30 11:22 ` [PATCH V3 00/23] IOREQ feature (+ virtio-mmio) on Arm Oleksandr
2020-12-07 13:03 ` Wei Chen
2020-12-07 21:03 ` Oleksandr
2020-11-30 16:21 ` Alex Bennée
2020-11-30 22:22 ` [PATCH V3 00/23] IOREQ feature (+ virtio-mmio) on Arm Oleksandr
2020-12-29 15:32 ` Roger Pau Monné
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