Re: [External] Re: [PATCH v2] riscv: mm: add paging_check() before paging_init()

From: yunhui cui
Date: Wed Aug 14 2024 - 00:16:18 EST

Hi Alex,

On Tue, Aug 13, 2024 at 10:21 PM Alexandre Ghiti <alexghiti@xxxxxxxxxxxx> wrote:
>
> Hi Yunhui,
>
> Sorry I was off last week.
>
> On Sat, Aug 3, 2024 at 8:28 AM yunhui cui <cuiyunhui@xxxxxxxxxxxxx> wrote:
> >
> > Hi Alex,
> >
> > On Thu, Aug 1, 2024 at 4:02 PM Alexandre Ghiti <alexghiti@xxxxxxxxxxxx> wrote:
> > >
> > > Hi Yunhui,
> > >
> > > On Thu, Jul 25, 2024 at 9:42 AM Yunhui Cui <cuiyunhui@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxx>
> > > > ---
> > > > 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@xxxxxxxx/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.
>
> Yes, you're right, we should advertise people when something like this
> happens. What do you think of the following instead?
>
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index de8a608eec1a..29c8e321eadc 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -254,8 +254,11 @@ static void __init setup_bootmem(void)
> */
> if (IS_ENABLED(CONFIG_64BIT)) {
> max_mapped_addr = __pa(PAGE_OFFSET) + KERN_VIRT_SIZE;
> - memblock_cap_memory_range(phys_ram_base,
> - max_mapped_addr - phys_ram_base);
> + if (memblock_end_of_DRAM() > max_mapped_addr) {
> + memblock_cap_memory_range(phys_ram_base,
> + max_mapped_addr -
> phys_ram_base);
> + pr_warn("Physical memory overflows the linear
> mapping size: region above 0x%llx removed", max_mapped_addr);
> + }
Yeah, but it's better to be more eye-catching, All right, I'll update
this patch.

> }
>
> /*
>
> Thanks,
>
> Alex
>
> >
> > >
> > > Thanks,
> > >
> > > Alex
> >
> > Thanks,
> > Yunhui

Thanks,
Yunhui