Messages in this thread | | | Subject | Re: [PATCH v2 2/2] ARM: support PHYS_OFFSET minimum aligned at 64KiB boundary | From | "Leizhen (ThunderTown)" <> | Date | Mon, 28 Sep 2020 17:30:20 +0800 |
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On 2020/9/28 9:30, Leizhen (ThunderTown) wrote: > > > On 2020/9/22 20:30, Leizhen (ThunderTown) wrote: >> >> >> On 2020/9/21 16:53, Leizhen (ThunderTown) wrote: >>> >>> >>> On 2020/9/21 14:47, Ard Biesheuvel wrote: >>>> On Mon, 21 Sep 2020 at 05:35, Leizhen (ThunderTown) >>>> <thunder.leizhen@huawei.com> wrote: >>>>> >>>>> >>>>> >>>>> On 2020/9/17 22:00, Ard Biesheuvel wrote: >>>>>> On Tue, 15 Sep 2020 at 22:06, Russell King - ARM Linux admin >>>>>> <linux@armlinux.org.uk> wrote: >>>>>>> >>>>>>> On Tue, Sep 15, 2020 at 09:16:15PM +0800, Zhen Lei wrote: >>>>>>>> Currently, only support the kernels where the base of physical memory is >>>>>>>> at a 16MiB boundary. Because the add/sub instructions only contains 8bits >>>>>>>> unrotated value. But we can use one more "add/sub" instructions to handle >>>>>>>> bits 23-16. The performance will be slightly affected. >>>>>>>> >>>>>>>> Since most boards meet 16 MiB alignment, so add a new configuration >>>>>>>> option ARM_PATCH_PHYS_VIRT_RADICAL (default n) to control it. Say Y if >>>>>>>> anyone really needs it. >>>>>>>> >>>>>>>> All r0-r7 (r1 = machine no, r2 = atags or dtb, in the start-up phase) are >>>>>>>> used in __fixup_a_pv_table() now, but the callee saved r11 is not used in >>>>>>>> the whole head.S file. So choose it. >>>>>>>> >>>>>>>> Because the calculation of "y = x + __pv_offset[63:24]" have been done, >>>>>>>> so we only need to calculate "y = y + __pv_offset[23:16]", that's why >>>>>>>> the parameters "to" and "from" of __pv_stub() and __pv_add_carry_stub() >>>>>>>> in the scope of CONFIG_ARM_PATCH_PHYS_VIRT_RADICAL are all passed "t" >>>>>>>> (above y). >>>>>>>> >>>>>>>> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> >>>>>>>> --- >>>>>>>> arch/arm/Kconfig | 18 +++++++++++++++++- >>>>>>>> arch/arm/include/asm/memory.h | 16 +++++++++++++--- >>>>>>>> arch/arm/kernel/head.S | 25 +++++++++++++++++++------ >>>>>>>> 3 files changed, 49 insertions(+), 10 deletions(-) >>>>>>>> >>>>>>>> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig >>>>>>>> index e00d94b16658765..19fc2c746e2ce29 100644 >>>>>>>> --- a/arch/arm/Kconfig >>>>>>>> +++ b/arch/arm/Kconfig >>>>>>>> @@ -240,12 +240,28 @@ config ARM_PATCH_PHYS_VIRT >>>>>>>> kernel in system memory. >>>>>>>> >>>>>>>> This can only be used with non-XIP MMU kernels where the base >>>>>>>> - of physical memory is at a 16MB boundary. >>>>>>>> + of physical memory is at a 16MiB boundary. >>>>>>>> >>>>>>>> Only disable this option if you know that you do not require >>>>>>>> this feature (eg, building a kernel for a single machine) and >>>>>>>> you need to shrink the kernel to the minimal size. >>>>>>>> >>>>>>>> +config ARM_PATCH_PHYS_VIRT_RADICAL >>>>>>>> + bool "Support PHYS_OFFSET minimum aligned at 64KiB boundary" >>>>>>>> + default n >>>>>>> >>>>>>> Please drop the "default n" - this is the default anyway. >>>>>>> >>>>>>>> @@ -236,6 +243,9 @@ static inline unsigned long __phys_to_virt(phys_addr_t x) >>>>>>>> * in place where 'r' 32 bit operand is expected. >>>>>>>> */ >>>>>>>> __pv_stub((unsigned long) x, t, "sub", __PV_BITS_31_24); >>>>>>>> +#ifdef CONFIG_ARM_PATCH_PHYS_VIRT_RADICAL >>>>>>>> + __pv_stub((unsigned long) t, t, "sub", __PV_BITS_23_16); >>>>>>> >>>>>>> t is already unsigned long, so this cast is not necessary. >>>>>>> >>>>>>> I've been debating whether it would be better to use "movw" for this >>>>>>> for ARMv7. In other words: >>>>>>> >>>>>>> movw tmp, #16-bit >>>>>>> adds %Q0, %1, tmp, lsl #16 >>>>>>> adc %R0, %R0, #0 >>>>>>> >>>>>>> It would certainly be less instructions, but at the cost of an >>>>>>> additional register - and we'd have to change the fixup code to >>>>>>> know about movw. >>>>>>> >>>>>>> Thoughts? >>>>>>> >>>>>> >>>>>> Since LPAE implies v7, we can use movw unconditionally, which is nice. >>>>>> >>>>>> There is no need to use an additional temp register, as we can use the >>>>>> register holding the high word. (There is no need for the mov_hi macro >>>>>> to be separate) >>>>>> >>>>>> 0: movw %R0, #low offset >> 16 >>>>>> adds %Q0, %1, %R0, lsl #16 >>>>>> 1: mov %R0, #high offset >>>>>> adc %R0, %R0, #0 >>>>>> .pushsection .pv_table,"a" >>>>>> .long 0b, 1b >>>>>> .popsection >>>>>> >>>>>> The only problem is distinguishing the two mov instructions from each >>>>> >>>>> The #high offset can also consider use movw, it just save two bytes in >>>>> the thumb2 scenario. We can store different imm16 value for high_offset >>>>> and low_offset, so that we can distinguish them in __fixup_a_pv_table(). >>>>> >>>>> This will make the final implementation of the code look more clear and >>>>> consistent, especially THUMB2. >>>>> >>>>> Let me try it. >>>>> >>>> >>>> Hello Zhen Lei, >>>> >>>> I am looking into this as well: >>>> >>>> https://git.kernel.org/pub/scm/linux/kernel/git/ardb/linux.git/log/?h=arm-p2v-v2 >>>> >>>> Could you please test this version on your hardware? >>> >>> OK, I will test it on my boards. >> Hi Ard Biesheuvel: >> I have tested it on 16MiB aligned + LE board, it works well. I've asked my colleagues >> from other departments to run it on 2MiB aligned + BE board. He will do it tomorrow. > > Hi, Ard Biesheuvel: > I'm sorry to keep you waiting so long. You patch series works well on 2MiB aligned + BE board > also. I spent a lot of time, because our 2MiB aligned + BE board loads zImage. Therefore, special > processing is required for the following code: > > arch/arm/boot/compressed/head.S: > #ifdef CONFIG_AUTO_ZRELADDR > mov r4, pc > and r4, r4, #0xf8000000 //currently only support 128MiB alignment > add r4, r4, #TEXT_OFFSET > #else > > This is a special scenario that does not conflict with your code framework. So I'm trying to fix it. > > Tested-by: Zhen Lei <thunder.leizhen@huawei.com>
Hi, Ard Biesheuvel: I just sent the above problem's fix patch.
[PATCH 0/2] ARM: decompressor: relax the loading restriction of the decompressed kernel
> > >> >> >>> >>>> >>>> . >>>> >>> >>> >>> _______________________________________________ >>> linux-arm-kernel mailing list >>> linux-arm-kernel@lists.infradead.org >>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >>> >>> . >>>
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