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Message-ID: <YgoARncp0jCMTDEX@MiWiFi-R3L-srv>
Date: Mon, 14 Feb 2022 15:09:58 +0800
From: Baoquan He <bhe@...hat.com>
To: "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>
Cc: Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
x86@...nel.org, "H . Peter Anvin" <hpa@...or.com>,
linux-kernel@...r.kernel.org, Dave Young <dyoung@...hat.com>,
Vivek Goyal <vgoyal@...hat.com>,
Eric Biederman <ebiederm@...ssion.com>,
kexec@...ts.infradead.org,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>,
linux-arm-kernel@...ts.infradead.org,
Rob Herring <robh+dt@...nel.org>,
Frank Rowand <frowand.list@...il.com>,
devicetree@...r.kernel.org, Jonathan Corbet <corbet@....net>,
linux-doc@...r.kernel.org, Randy Dunlap <rdunlap@...radead.org>,
Feng Zhou <zhoufeng.zf@...edance.com>,
Kefeng Wang <wangkefeng.wang@...wei.com>,
Chen Zhou <dingguo.cz@...group.com>,
John Donnelly <John.p.donnelly@...cle.com>,
Dave Kleikamp <dave.kleikamp@...cle.com>
Subject: Re: [PATCH v20 3/5] arm64: kdump: reimplement crashkernel=X
On 02/14/22 at 02:44pm, Leizhen (ThunderTown) wrote:
>
>
> On 2022/2/11 18:51, Baoquan He wrote:
> > On 02/11/22 at 06:41pm, Leizhen (ThunderTown) wrote:
> >>
> >>
> >> On 2022/2/11 18:30, Baoquan He wrote:
> >>> On 01/24/22 at 04:47pm, Zhen Lei wrote:
> >>>> From: Chen Zhou <chenzhou10@...wei.com>
> >>> ......
> >>>> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> >>>> index 6c653a2c7cff052..a5d43feac0d7d96 100644
> >>>> --- a/arch/arm64/mm/init.c
> >>>> +++ b/arch/arm64/mm/init.c
> >>>> @@ -71,6 +71,30 @@ phys_addr_t arm64_dma_phys_limit __ro_after_init;
> >>>> #define CRASH_ADDR_LOW_MAX arm64_dma_phys_limit
> >>>> #define CRASH_ADDR_HIGH_MAX MEMBLOCK_ALLOC_ACCESSIBLE
> >>>>
> >>>> +static int __init reserve_crashkernel_low(unsigned long long low_size)
> >>>> +{
> >>>> + unsigned long long low_base;
> >>>> +
> >>>> + /* passed with crashkernel=0,low ? */
> >>>> + if (!low_size)
> >>>> + return 0;
> >>>> +
> >>>> + low_base = memblock_phys_alloc_range(low_size, CRASH_ALIGN, 0, CRASH_ADDR_LOW_MAX);
> >>>> + if (!low_base) {
> >>>> + pr_err("cannot allocate crashkernel low memory (size:0x%llx).\n", low_size);
> >>>> + return -ENOMEM;
> >>>> + }
> >>>> +
> >>>> + pr_info("crashkernel low memory reserved: 0x%llx - 0x%llx (%lld MB)\n",
> >>>> + low_base, low_base + low_size, low_size >> 20);
> >>>> +
> >>>> + crashk_low_res.start = low_base;
> >>>> + crashk_low_res.end = low_base + low_size - 1;
> >>>> + insert_resource(&iomem_resource, &crashk_low_res);
> >>>> +
> >>>> + return 0;
> >>>> +}
> >>>> +
> >>>> /*
> >>>> * reserve_crashkernel() - reserves memory for crash kernel
> >>>> *
> >>>> @@ -81,29 +105,62 @@ phys_addr_t arm64_dma_phys_limit __ro_after_init;
> >>>> static void __init reserve_crashkernel(void)
> >>>> {
> >>>> unsigned long long crash_base, crash_size;
> >>>> + unsigned long long crash_low_size = SZ_256M;
> >>>> unsigned long long crash_max = CRASH_ADDR_LOW_MAX;
> >>>> int ret;
> >>>> + bool fixed_base;
> >>>> + char *cmdline = boot_command_line;
> >>>>
> >>>> - ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
> >>>> + /* crashkernel=X[@offset] */
> >>>> + ret = parse_crashkernel(cmdline, memblock_phys_mem_size(),
> >>>> &crash_size, &crash_base);
> >>>> - /* no crashkernel= or invalid value specified */
> >>>> - if (ret || !crash_size)
> >>>> - return;
> >>>> + if (ret || !crash_size) {
> >>>> + unsigned long long low_size;
> >>>>
> >>>> + /* crashkernel=X,high */
> >>>> + ret = parse_crashkernel_high(cmdline, 0, &crash_size, &crash_base);
> >>>> + if (ret || !crash_size)
> >>>> + return;
> >>>> +
> >>>> + /* crashkernel=X,low */
> >>>> + ret = parse_crashkernel_low(cmdline, 0, &low_size, &crash_base);
> >>>> + if (!ret)
> >>>> + crash_low_size = low_size;
> >>>
> >>> Here, the error case is not checked and handled. But it still gets
> >>> expeced result which is the default SZ_256M. Is this designed on
> >>> purpose?
> >>
> >> Yes, we can specify only "crashkernel=X,high".
> >>
> >> This is mentioned in Documentation/admin-guide/kernel-parameters.txt
> >>
> >> crashkernel=size[KMG],low
> >> [KNL, X86-64] range under 4G. When crashkernel=X,high
> >> is passed, kernel could allocate physical memory region
> >> above 4G, that cause second kernel crash on system
> >> that require some amount of low memory, e.g. swiotlb
> >> requires at least 64M+32K low memory, also enough extra
> >> low memory is needed to make sure DMA buffers for 32-bit
> >> devices won't run out. Kernel would try to allocate at <---------
> >> least 256M below 4G automatically. <---------
> >
> > Yeah, that is expected becasue no crahskernel=,low is a right usage. The
> > 'ret' is 0 in the case. If I gave below string, it works too.
> > "crashkernel=256M,high crashkernel=aaabbadfadfd,low"
>
> Yes, so maybe we should change the error code in __parse_crashkernel()
> from "-EINVAL" to "-ENOENT" when the specified option does not exist.
Good point. I also thought of this, it could be next step clean up. X86
code need this too. In crashkernel='messy code',high, it will fail to
reserve. For consistency, we should fail crashkrenel='messy code',low
too.
>
> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
> index 256cf6db573cd09..395f4fac1773f28 100644
> --- a/kernel/crash_core.c
> +++ b/kernel/crash_core.c
> @@ -243,9 +243,8 @@ static int __init __parse_crashkernel(char *cmdline,
> *crash_base = 0;
>
> ck_cmdline = get_last_crashkernel(cmdline, name, suffix);
> -
> if (!ck_cmdline)
> - return -EINVAL;
> + return -ENOENT;
>
> ck_cmdline += strlen(name);
>
>
> >
> >>
> >>>
> >>>> +
> >>>> + crash_max = CRASH_ADDR_HIGH_MAX;
> >>>> + }
> >>>> +
> >>>> + fixed_base = !!crash_base;
> >>>> crash_size = PAGE_ALIGN(crash_size);
> >>>>
> >>>> /* User specifies base address explicitly. */
> >>>> if (crash_base)
> >>>> crash_max = crash_base + crash_size;
> >>>>
> >>>> +retry:
> >>>> crash_base = memblock_phys_alloc_range(crash_size, CRASH_ALIGN,
> >>>> crash_base, crash_max);
> >>>> if (!crash_base) {
> >>>> + /*
> >>>> + * Attempt to fully allocate low memory failed, fall back
> >>>> + * to high memory, the minimum required low memory will be
> >>>> + * reserved later.
> >>>> + */
> >>>> + if (!fixed_base && (crash_max == CRASH_ADDR_LOW_MAX)) {
> >>>> + crash_max = CRASH_ADDR_HIGH_MAX;
> >>>> + goto retry;
> >>>> + }
> >>>> +
> >>>> pr_warn("cannot allocate crashkernel (size:0x%llx)\n",
> >>>> crash_size);
> >>>> return;
> >>>> }
> >>>>
> >>>> + if (crash_base >= SZ_4G && reserve_crashkernel_low(crash_low_size)) {
> >>>> + memblock_phys_free(crash_base, crash_size);
> >>>> + return;
> >>>> + }
> >>>> +
> >>>> pr_info("crashkernel reserved: 0x%016llx - 0x%016llx (%lld MB)\n",
> >>>> crash_base, crash_base + crash_size, crash_size >> 20);
> >>>>
> >>>> @@ -112,6 +169,9 @@ static void __init reserve_crashkernel(void)
> >>>> * map. Inform kmemleak so that it won't try to access it.
> >>>> */
> >>>> kmemleak_ignore_phys(crash_base);
> >>>> + if (crashk_low_res.end)
> >>>> + kmemleak_ignore_phys(crashk_low_res.start);
> >>>> +
> >>>> crashk_res.start = crash_base;
> >>>> crashk_res.end = crash_base + crash_size - 1;
> >>>> insert_resource(&iomem_resource, &crashk_res);
> >>>> --
> >>>> 2.25.1
> >>>>
> >>>
> >>> .
> >>>
> >>
> >> --
> >> Regards,
> >> Zhen Lei
> >>
> >
> > .
> >
>
> --
> Regards,
> Zhen Lei
>
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