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Message-ID: <YgY/qQUkBF0eZ9zc@MiWiFi-R3L-srv>
Date: Fri, 11 Feb 2022 18:51:21 +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 02/11/22 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"
>
> >
> >> +
> >> + 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
>
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