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Message-ID: <CAEEQ3wkDprXSGmPO8ufYqJMiTjuxoQwFHG+OAtfd9p0ggC8y_g@mail.gmail.com>
Date: Sat, 3 Aug 2024 14:28:26 +0800
From: yunhui cui <cuiyunhui@...edance.com>
To: Alexandre Ghiti <alexghiti@...osinc.com>
Cc: punit.agrawal@...edance.com, paul.walmsley@...ive.com, palmer@...belt.com,
aou@...s.berkeley.edu, samitolvanen@...gle.com, gregkh@...uxfoundation.org,
suagrfillet@...il.com, akpm@...ux-foundation.org, shikemeng@...weicloud.com,
willy@...radead.org, charlie@...osinc.com, xiao.w.wang@...el.com,
conor.dooley@...rochip.com, chenjiahao16@...wei.com, guoren@...nel.org,
jszhang@...nel.org, ajones@...tanamicro.com, bhe@...hat.com,
vishal.moola@...il.com, ndesaulniers@...gle.com,
linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [External] Re: [PATCH v2] riscv: mm: add paging_check() before paging_init()
Hi Alex,
On Thu, Aug 1, 2024 at 4:02 PM Alexandre Ghiti <alexghiti@...osinc.com> wrote:
>
> Hi Yunhui,
>
> On Thu, Jul 25, 2024 at 9:42 AM Yunhui Cui <cuiyunhui@...edance.com> wrote:
> >
> > When establishing a linear mapping, the virtual address is obtained
> > through __va(). If the physical address is too large, such as 1TB, then
> > the virtual address will overflow in the address space of sv39.
> > The log is as follows:
> > [ 0.000000] Unable to handle kernel paging request at virtual address 000000d97fdf7ad8
> > [ 0.000000] [000000d97fdf7ad8] pgd=000000407ff7e801, p4d=000000407ff7e801, pud=000000407ff7e801
> > [ 0.000000] Unable to handle kernel paging request at virtual address 000000d97fdfaff0
> > [ 0.000000] [000000d97fdfaff0] pgd=000000407ff7e801, p4d=000000407ff7e801, pud=000000407ff7e801
> > ...
> > [ 0.000000] Insufficient stack space to handle exception!
> > [ 0.000000] Task stack: [0xffffffff81400000..0xffffffff81404000]
> > [ 0.000000] Overflow stack: [0xffffffff80c67370..0xffffffff80c68370]
> > [ 0.000000] CPU: 0 PID: 0 Comm: swapper Tainted: G W 6.6.3-00133-g60497fad461d-dirty #71
> > [ 0.000000] epc : die_kernel_fault+0x158/0x1c8
> > [ 0.000000] ra : die_kernel_fault+0x12a/0x1c8
> > [ 0.000000] epc : ffffffff808cde36 ra : ffffffff808cde08 sp : ffffffff813fff80
> > [ 0.000000] gp : ffffffff815a1678 tp : 0000000000000000 t0 : 0000003130386537
> > [ 0.000000] t1 : 0000000000000031 t2 : 6537666637303430 s0 : ffffffff813fffc0
> > [ 0.000000] s1 : ffffffff815b0b28 a0 : 0000000000000016 a1 : ffffffff81495298
> > [ 0.000000] a2 : 0000000000000010 a3 : ffffffff81495298 a4 : 00000000000001fe
> > [ 0.000000] a5 : 000000d97fdfa000 a6 : ffffffff814250d0 a7 : 0000000000000030
> > [ 0.000000] s2 : 000000d97fdfaff0 s3 : ffffffff81400040 s4 : 000000d97fdfaff0
> > [ 0.000000] s5 : ffffffff815a0ed0 s6 : 0000000000000000 s7 : 000000008f604390
> > [ 0.000000] s8 : 0000000000000000 s9 : ffffffffffffffff s10: 0000000000000000
> > [ 0.000000] s11: 0000000000000000 t3 : ffffffff815baa9b t4 : ffffffff815baa9b
> > [ 0.000000] t5 : ffffffff815baa88 t6 : ffffffff813ffda8
> > [ 0.000000] status: 0000000200000100 badaddr: 000000d97fdfaff0 cause: 000000000000000d
> > [ 0.000000] Kernel panic - not syncing: Kernel stack overflow
> > [ 0.000000] CPU: 0 PID: 0 Comm: swapper Tainted: G W 6.6.3-00133-g60497fad461d-dirty #71
> > [ 0.000000] Call Trace:
> > [ 0.000000] [<ffffffff800066bc>] dump_backtrace+0x28/0x30
> > [ 0.000000] [<ffffffff808cdac8>] show_stack+0x38/0x44
> > [ 0.000000] [<ffffffff808d9d40>] dump_stack_lvl+0x44/0x5c
> > [ 0.000000] [<ffffffff808d9d70>] dump_stack+0x18/0x20
> > [ 0.000000] [<ffffffff808cdfb6>] panic+0x110/0x2f2
> > [ 0.000000] [<ffffffff80006532>] walk_stackframe+0x0/0x120
> > [ 0.000000] [<ffffffff808cde08>] die_kernel_fault+0x12a/0x1c8
> > [ 0.000000] ---[ end Kernel panic - not syncing: Kernel stack overflow ]---
> >
> > In other words, the maximum value of the physical address needs to meet
> > Documentation/riscv/vm-layout.rst to ensure that there is no overflow.
> > For sv48/57, the actual virtual address space is huge, so this problem
> > is generally not triggered, but it is also checked in the code.
> >
> > We give a warning for the overflowed physical address region and reverve it
> > so that the kernel can bringup successfully.
> >
> > Signed-off-by: Yunhui Cui <cuiyunhui@...edance.com>
> > ---
> > arch/riscv/include/asm/page.h | 9 +++++++++
> > arch/riscv/include/asm/pgtable.h | 1 +
> > arch/riscv/kernel/setup.c | 1 +
> > arch/riscv/mm/init.c | 30 ++++++++++++++++++++++++++++++
> > 4 files changed, 41 insertions(+)
> >
> > diff --git a/arch/riscv/include/asm/page.h b/arch/riscv/include/asm/page.h
> > index 57e887bfa34c..f6c0f6e14ecb 100644
> > --- a/arch/riscv/include/asm/page.h
> > +++ b/arch/riscv/include/asm/page.h
> > @@ -38,6 +38,15 @@
> > */
> > #define PAGE_OFFSET_L4 _AC(0xffffaf8000000000, UL)
> > #define PAGE_OFFSET_L3 _AC(0xffffffd800000000, UL)
> > +
> > +/*
> > + * See vm-layout.rst, the size of L3 direct mapping of all physical
> > + * memory 124GB, L4 is 64TB, L5 is 32PB.
> > + */
> > +#define MAX_PFN_MEM_ADDR_L5 (0x80000000000000ULL)
> > +#define MAX_PFN_MEM_ADDR_L4 (0x400000000000ULL)
> > +#define MAX_PFN_MEM_ADDR_L3 (0x1F00000000ULL)
> > +
> > #else
> > #define PAGE_OFFSET _AC(CONFIG_PAGE_OFFSET, UL)
> > #endif /* CONFIG_64BIT */
> > diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> > index c8e8867c42f6..e4835de5a743 100644
> > --- a/arch/riscv/include/asm/pgtable.h
> > +++ b/arch/riscv/include/asm/pgtable.h
> > @@ -915,6 +915,7 @@ extern uintptr_t _dtb_early_pa;
> > #endif /* CONFIG_XIP_KERNEL */
> > extern u64 satp_mode;
> >
> > +void paging_check(void);
> > void paging_init(void);
> > void misc_mem_init(void);
> >
> > diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
> > index 2a79d4ed2660..366918578544 100644
> > --- a/arch/riscv/kernel/setup.c
> > +++ b/arch/riscv/kernel/setup.c
> > @@ -273,6 +273,7 @@ void __init setup_arch(char **cmdline_p)
> > parse_early_param();
> >
> > efi_init();
> > + paging_check();
> > paging_init();
> >
> > /* Parse the ACPI tables for possible boot-time configuration */
> > diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> > index b0cc28f7595f..aa25dcf8a0ff 100644
> > --- a/arch/riscv/mm/init.c
> > +++ b/arch/riscv/mm/init.c
> > @@ -1482,6 +1482,36 @@ static void __init reserve_crashkernel(void)
> > crashk_res.end = crash_base + crash_size - 1;
> > }
> >
> > +static void __init phymem_addr_overflow(void)
> > +{
> > + phys_addr_t end = memblock_end_of_DRAM();
> > +
> > + if (pgtable_l5_enabled) {
> > + if (end > MAX_PFN_MEM_ADDR_L5) {
> > + memblock_reserve(MAX_PFN_MEM_ADDR_L5, end - MAX_PFN_MEM_ADDR_L5);
> > + WARN(true, "Phymem addr 0x%llx overflowed, reserve [0x%llx-0x%llx] directly.",
> > + end, MAX_PFN_MEM_ADDR_L5, end);
> > + }
> > + }
> > + if (pgtable_l4_enabled) {
> > + if (end > MAX_PFN_MEM_ADDR_L4) {
> > + memblock_reserve(MAX_PFN_MEM_ADDR_L4, end - MAX_PFN_MEM_ADDR_L4);
> > + WARN(true, "Phymem addr 0x%llx overflowed, reserve [0x%llx-0x%llx] directly.",
> > + end, MAX_PFN_MEM_ADDR_L4, end);
> > + }
> > + }
> > + if (end > MAX_PFN_MEM_ADDR_L3) {
> > + memblock_reserve(MAX_PFN_MEM_ADDR_L3, end - MAX_PFN_MEM_ADDR_L3);
> > + WARN(true, "Phymem addr 0x%llx overflowed, reserve [0x%llx-0x%llx] directly.",
> > + end, MAX_PFN_MEM_ADDR_L3, end);
> > + }
> > +}
> > +
> > +void __init paging_check(void)
> > +{
> > + phymem_addr_overflow();
> > +}
> > +
> > void __init paging_init(void)
> > {
> > setup_bootmem();
> > --
> > 2.39.2
> >
>
> So the following patch should fix your issue and was posted some time
> ago https://lore.kernel.org/linux-riscv/bdfbed9b-ea04-4415-8416-d6e9d0a643a3@ghiti.fr/T/#me26a82cf32f46cae12e2ea8892a3bc16d4fc37e3.
> I prefer this solution as it does not introduce a bunch of hardcoded
> defines and relies on the already existing memblock API.
>
> Let me know if that's not the case!
I understand that there is no problem with the functionality of this
patch, but since the actual physical memory is lost, we need a Warning
message to avoid confusion about memory disappearance for no reason.
>
> Thanks,
>
> Alex
Thanks,
Yunhui
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