Re: [PATCH v6 00/14] riscv: support for Svpbmt and D1 memory types

From: Atish Patra
Date: Mon Feb 14 2022 - 16:04:45 EST

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On Mon, Feb 14, 2022 at 12:02 PM Heiko Stübner <heiko@xxxxxxxxx> wrote:
>
> Hi Atish,
>
> Am Samstag, 12. Februar 2022, 01:25:53 CET schrieb Atish Patra:
> > On Thu, Feb 10, 2022 at 6:04 PM Heiko Stübner <heiko@xxxxxxxxx> wrote:
> > >
> > > Am Freitag, 11. Februar 2022, 02:48:38 CET schrieb Atish Patra:
> > > > On Thu, Feb 10, 2022 at 4:25 PM Atish Patra <atishp@xxxxxxxxxxxxxx> wrote:
> > > > >
> > > > > On Wed, Feb 9, 2022 at 4:38 AM Heiko Stuebner <heiko@xxxxxxxxx> wrote:
> > > > > >
> > > > > > Svpbmt is an extension defining "Supervisor-mode: page-based memory types"
> > > > > > for things like non-cacheable pages or I/O memory pages.
> > > > > >
> > > > > >
> > > > > > So this is my 2nd try at implementing Svpbmt (and the diverging D1 memory
> > > > > > types) using the alternatives framework.
> > > > > >
> > > > > > This includes a number of changes to the alternatives mechanism itself.
> > > > > > The biggest one being the move to a more central location, as I expect
> > > > > > in the future, nearly every chip needing some sort of patching, be it
> > > > > > either for erratas or for optional features (svpbmt or others).
> > > > > >
> > > > > > The dt-binding for svpbmt itself is of course not finished and is still
> > > > > > using the binding introduced in previous versions, as where to put
> > > > > > a svpbmt-property in the devicetree is still under dicussion.
> > > > > > Atish seems to be working on a framework for extensions [0],
> > > > > >
> > > > >
> > > > > Here is the patch series
> > > > > https://lore.kernel.org/lkml/20220210214018.55739-1-atishp@xxxxxxxxxxxx/
> > > > >
> > > > > I think we can simplify the cpu feature probing in PATCH 10 with the
> > > > > above series
> > > > > which simply relies on the existing riscv_isa bitmap.
> > > > >
> > > > > We also don't need the separate svpbmt property in DT mmu node.
> > > > > Let me know what you think.
> > > > >
> > > > > > The series also introduces support for the memory types of the D1
> > > > > > which are implemented differently to svpbmt. But when patching anyway
> > > > > > it's pretty clean to add the D1 variant via ALTERNATIVE_2 to the same
> > > > > > location.
> > > > > >
> > > > > > The only slightly bigger difference is that the "normal" type is not 0
> > > > > > as with svpbmt, so kernel patches for this PMA type need to be applied
> > > > > > even before the MMU is brought up, so the series introduces a separate
> > > > > > stage for that.
> > > > > >
> > > > > >
> > > > > > In theory this series is 3 parts:
> > > > > > - sbi cache-flush / null-ptr
> > > > > > - alternatives improvements
> > > > > > - svpbmt+d1
> > > > > >
> > > > > > So expecially patches from the first 2 areas could be applied when
> > > > > > deemed ready, I just thought to keep it together to show-case where
> > > > > > the end-goal is and not requiring jumping between different series.
> > > > > >
> > > > > >
> > > > > > The sbi cache-flush patch is based on Atish's sparse-hartid patch [1],
> > > > > > as it touches a similar area in mm/cacheflush.c
> > > > > >
> > > > > >
> > > > > > I picked the recipient list from the previous version, hopefully
> > > > > > I didn't forget anybody.
> > > > > >
> > > >
> > > > I am also getting a load access fault while booting this series in Qemu.
> > > >
> > > > <with additional debug message when before sbi_trap_redirect in OpenSBI>
> > > > sbi_trap_error_debug: hart1: trap handler failed (error -2)
> > > > sbi_trap_error_debug: hart1: mcause=0x0000000000000005 mtval=0x0000000080046468
> > > > sbi_trap_error_debug: hart1: mtval2=0x0000000000000000 mtinst=0x0000000000000000
> > > > sbi_trap_error_debug: hart1: mepc=0x000000008080a8b8 mstatus=0x0000000a00000800
> > > > sbi_trap_error_debug: hart1: ra=0x0000000080202b06 sp=0x0000000081203f00
> > > > sbi_trap_error_debug: hart1: gp=0x00000000812d9db8 tp=0x0000000080046000
> > > > sbi_trap_error_debug: hart1: s0=0x0000000081203f80 s1=0x0000000080c1a8a8
> > > > sbi_trap_error_debug: hart1: a0=0x0000000080c1a8a8 a1=0x0000000080c1b0d0
> > > > sbi_trap_error_debug: hart1: a2=0x0000000000000002 a3=0x0000000000000000
> > > > sbi_trap_error_debug: hart1: a4=0x00000000812da902 a5=0x0000000000000000
> > > > sbi_trap_error_debug: hart1: a6=0x0000000000000006 a7=0x0000000000000010
> > > > sbi_trap_error_debug: hart1: s2=0x0000000080c1b0d0 s3=0x0000000000000002
> > > > sbi_trap_error_debug: hart1: s4=0x00000000bf000000 s5=0x0000000000000000
> > > > sbi_trap_error_debug: hart1: s6=0x8000000a00006800 s7=0x000000000000007f
> > > > sbi_trap_error_debug: hart1: s8=0x0000000080018038 s9=0x0000000080039eac
> > > > sbi_trap_error_debug: hart1: s10=0x0000000000000000 s11=0x0000000000000000
> > > > sbi_trap_error_debug: hart1: t0=0x0000000080c04000 t1=0x0000000000000002
> > > > sbi_trap_error_debug: hart1: t2=0x0000000000001000 t3=0x0000000000000010
> > > > sbi_trap_error_debug: hart1: t4=0x00000000800168be t5=0x0000000000000027
> > > > sbi_trap_error_debug: hart1: t6=0x0000000000000001
> > > >
> > > > mepc : 0x000000008080a8b8 - call_function_init (kernel/smp.c)
> > > >
> > > > Kernel - 5.17-rc2 + my patches
> > > > Qemu - Alistairs next tree + my patches
> > >
> > > very strange. I was testing of course with Qemu as well, though never saw
> > > anything like this.
> > >
> > > But of course it was Qemu master + the then still pending svpbmt patchset [0]
> > > [looks like Alistair applied this today] + a patch that made qemu insert the
> > > svpbmt dt-property for the virt machine.
> > >
> > > Oh ... just to make sure, did you enable the svpbmt parameter when starting
> > > Qemu? (-cpu ...,svpbmt=true)
> > >
> >
> > Yeah. I tried with or without. It's failing in both cases. I found a
> > fix but that may be unrelated and hiding the real issue.
> > Marking the cpufeature_svpbmt_check_of functions inline allows me to boot.
> >
> > Here is my analysis:
> >
> > Here is the trace of the trap:
> > sbi_trap_error_debug: hart0: trap handler failed (error -2)
> > sbi_trap_error_debug: hart0: mcause=0x0000000000000005 mtval=0x0000000080048468
> > sbi_trap_error_debug: hart0: mtval2=0x0000000000000000 mtinst=0x0000000000000000
> > sbi_trap_error_debug: hart0: mepc=0x000000008080a8b8 mstatus=0x0000000a00000800
> > sbi_trap_error_debug: hart0: ra=0x0000000080202b06 sp=0x0000000081203f00
> > sbi_trap_error_debug: hart0: gp=0x00000000812d9db8 tp=0x0000000080048000
> > sbi_trap_error_debug: hart0: s0=0x0000000081203f80 s1=0x0000000080c1a8a8
> > sbi_trap_error_debug: hart0: a0=0x0000000080c1a8a8 a1=0x0000000080c1b0d0
> > sbi_trap_error_debug: hart0: a2=0x0000000000000002 a3=0x0000000000000000
> > sbi_trap_error_debug: hart0: a4=0x00000000812da902 a5=0x0000000000000000
> > sbi_trap_error_debug: hart0: a6=0x0000000000000006 a7=0x0000000000000010
> > sbi_trap_error_debug: hart0: s2=0x0000000080c1b0d0 s3=0x0000000000000002
> > sbi_trap_error_debug: hart0: s4=0x00000000bf000000 s5=0x0000000000000000
> > sbi_trap_error_debug: hart0: s6=0x8000000a00006800 s7=0x000000000000007f
> > sbi_trap_error_debug: hart0: s8=0x0000000080018038 s9=0x0000000080039ea8
> > sbi_trap_error_debug: hart0: s10=0x0000000000000000 s11=0x0000000000000000
> > sbi_trap_error_debug: hart0: t0=0x0000000080c04000 t1=0x0000000000000002
> > sbi_trap_error_debug: hart0: t2=0x0000000000001000 t3=0x0000000000000010
> > sbi_trap_error_debug: hart0: t4=0x00000000800168be t5=0x0000000000000027
> > sbi_trap_error_debug: hart0: t6=0x0000000000000001
> >
> > mepc : 0x000000008080a8b8 - should be ffffffff8060a8b8 in objdump
> > output after offset
> >
> > Here is the snippet of the objdump output for riscv_cpufeature_patch_func
> >
> > ========================================================================
> > inline output: (booting fails with above dump)
> >
> > void riscv_cpufeature_patch_func(struct alt_entry *begin, struct alt_entry *end,
> > unsigned int stage)
> > {
> > ffffffff8060a89a: 7119 addi sp,sp,-128
> > ffffffff8060a89c: f8a2 sd s0,112(sp)
> > ffffffff8060a89e: f4a6 sd s1,104(sp)
> > ffffffff8060a8a0: f0ca sd s2,96(sp)
> > ffffffff8060a8a2: e4d6 sd s5,72(sp)
> > ffffffff8060a8a4: fc86 sd ra,120(sp)
> > ffffffff8060a8a6: ecce sd s3,88(sp)
> > ffffffff8060a8a8: e8d2 sd s4,80(sp)
> > ffffffff8060a8aa: e0da sd s6,64(sp)
> > ffffffff8060a8ac: fc5e sd s7,56(sp)
> > ffffffff8060a8ae: f862 sd s8,48(sp)
> > ffffffff8060a8b0: f466 sd s9,40(sp)
> > ffffffff8060a8b2: f06a sd s10,32(sp)
> > ffffffff8060a8b4: ec6e sd s11,24(sp)
> > ffffffff8060a8b6: 0100 addi s0,sp,128
> > ffffffff8060a8b8: 46823783 ld a5,1128(tp) #
> > 468 <__efistub_.L0 +0x5> --------> Faulting instruction
> > ffffffff8060a8bc: f8f43423 sd a5,-120(s0)
> > ffffffff8060a8c0: 4781 li a5,0
> > ffffffff8060a8c2: 8932 mv s2,a2
> > ffffffff8060a8c4: 84aa mv s1,a0
> > ffffffff8060a8c6: 8aae mv s5,a1
> > switch (stage) {
> > ffffffff8060a8c8: ca1d beqz
> > a2,ffffffff8060a8fe <riscv_cpufeature_patch_func+0x64>
> > ffffffff8060a8ca: 4789 li a5,2
> > ffffffff8060a8cc: 18f60363 beq
> > a2,a5,ffffffff8060aa52 <riscv_cpufeature_patch_func+0x1b8>
> > for_each_of_cpu_node(node) {
> > ffffffff8060a8d0: 4501 li a0,0
> > ========================================================================
> >
> > noinline output (boots fine)
> > ========================================================================
> > void riscv_cpufeature_patch_func(struct alt_entry *begin, struct alt_entry *end,
> > unsigned int stage)
> > {
> > ffffffff8060a968: 7159 addi sp,sp,-112
> > ffffffff8060a96a: f0a2 sd s0,96(sp)
> > ffffffff8060a96c: eca6 sd s1,88(sp)
> > ffffffff8060a96e: e8ca sd s2,80(sp)
> > ffffffff8060a970: fc56 sd s5,56(sp)
> > ffffffff8060a972: f486 sd ra,104(sp)
> > ffffffff8060a974: e4ce sd s3,72(sp)
> > ffffffff8060a976: e0d2 sd s4,64(sp)
> > ffffffff8060a978: f85a sd s6,48(sp)
> > ffffffff8060a97a: f45e sd s7,40(sp)
> > ffffffff8060a97c: f062 sd s8,32(sp)
> > ffffffff8060a97e: ec66 sd s9,24(sp)
> > ffffffff8060a980: e86a sd s10,16(sp)
> > ffffffff8060a982: e46e sd s11,8(sp)
> > ffffffff8060a984: 1880 addi s0,sp,112
> > ffffffff8060a986: 8932 mv s2,a2
> > ffffffff8060a988: 84aa mv s1,a0
> > ffffffff8060a98a: 8aae mv s5,a1
> > switch (stage) {
> > ffffffff8060a98c: ca09 beqz
> > a2,ffffffff8060a99e <riscv_cpufeature_patch_func+0x36>
> > ffffffff8060a98e: 4789 li a5,2
> > ffffffff8060a990: 0ef60f63 beq
> > a2,a5,ffffffff8060aa8e <riscv_cpufeature_patch_func+0x126>
> > return cpufeature_svpbmt_check_of();
> > ffffffff8060a994: f07ff0ef jal
> > ra,ffffffff8060a89a <cpufeature_svpbmt_check_of>
> > cpu_req_feature |= (1U << idx);
> > ffffffff8060a998: 0005091b sext.w s2,a0
> > ffffffff8060a99c: a8d5 j
> > ffffffff8060aa90 <riscv_cpufeature_patch_func+0x128>
> > const void *fdt = dtb_early_va;
> >
> >
> > Any thoughts ? It looks like it may related to "tp"
>
> Faulting instruction "efistub", so maybe something between efi
> and the devicetree not agreeing?
>

I don't think they are related as the execution has not reached the
device tree parsing yet.
It crashes before executing anything inside the DT parsing code.

__efistub_ is just a prefix to make sure that there are no absolute
relocations in .init section.
It is also enabled in defconfig. So you should see that error as well.

> Though at least on my build I also have efistub enabled, so it
> should be the same. So it's very strange that you're seeing that
> trap, which I've never seen so far.
>

Maybe GCC has to do something with it. Because adding "nolnine" solves
it for me.
I am using v11.1.0.

>
> In any case, I tried your + Tsukasa's patches regarding the isa-extensions
> today, and obviously that works fine, so we will get rid of the devicetree-
> parts anyway I guess.
>

I will try those changes and update the thread.

> With the change below on top of that v2/v3 version-mix, I also get a
> working svpbmt of course. After hacking qemu to generate a
> suitable isa-string for me :-) .

I will send a patch to Qemu to append the extension strings to the device tree.

>
>
> Heiko
>
> -------------- 8< ------------------
> diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
> index 691fc9c8099b..656cd626eb1a 100644
> --- a/arch/riscv/include/asm/hwcap.h
> +++ b/arch/riscv/include/asm/hwcap.h
> @@ -51,6 +51,7 @@ extern unsigned long elf_hwcap;
> * available logical extension id.
> */
> enum riscv_isa_ext_id {
> + RISCV_ISA_EXT_SVPBMT = RISCV_ISA_EXT_BASE,
> RISCV_ISA_EXT_ID_MAX = RISCV_ISA_EXT_MAX,
> };
>
> diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
> index ced7e5be8641..b5130b15ca8d 100644
> --- a/arch/riscv/kernel/cpu.c
> +++ b/arch/riscv/kernel/cpu.c
> @@ -71,6 +71,7 @@ int riscv_of_parent_hartid(struct device_node *node)
> }
>
> static struct riscv_isa_ext_data isa_ext_arr[] = {
> + __RISCV_ISA_EXT_DATA("svpbmt", RISCV_ISA_EXT_SVPBMT),
> __RISCV_ISA_EXT_DATA("", RISCV_ISA_EXT_MAX),
> };
>
> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> index 2e4eaedbf7f5..d82033ece1fd 100644
> --- a/arch/riscv/kernel/cpufeature.c
> +++ b/arch/riscv/kernel/cpufeature.c
> @@ -192,6 +192,8 @@ void __init riscv_fill_hwcap(void)
> if (!ext_long) {
> this_hwcap |= isa2hwcap[(unsigned char)(*ext)];
> this_isa |= (1UL << (*ext - 'a'));
> + } else {
> + SET_ISA_EXT_MAP("svpbmt", RISCV_ISA_EXT_SVPBMT);
> }
> #undef SET_ISA_EXT_MAP
> }
> @@ -253,64 +255,6 @@ struct cpufeature_info {
> bool (*check_func)(unsigned int stage);
> };
>
> -#if defined(CONFIG_MMU) && defined(CONFIG_64BIT)
> -static bool __init_or_module cpufeature_svpbmt_check_fdt(void)
> -{
> - const void *fdt = dtb_early_va;
> - const char *str;
> - int offset;
> -
> - offset = fdt_path_offset(fdt, "/cpus");
> - if (offset < 0)
> - return false;
> -
> - for (offset = fdt_next_node(fdt, offset, NULL); offset >= 0;
> - offset = fdt_next_node(fdt, offset, NULL)) {
> - str = fdt_getprop(fdt, offset, "device_type", NULL);
> - if (!str || strcmp(str, "cpu"))
> - break;
> -
> - str = fdt_getprop(fdt, offset, "mmu-type", NULL);
> - if (!str)
> - continue;
> -
> - if (!strncmp(str + 6, "none", 4))
> - continue;
> -
> - str = fdt_getprop(fdt, offset, "riscv,mmu", NULL);
> - if (!str)
> - continue;
> -
> - if (!strncmp(str + 6, "svpbmt", 6))
> - return true;
> - }
> -
> - return false;
> -}
> -
> -static bool __init_or_module cpufeature_svpbmt_check_of(void)
> -{
> - struct device_node *node;
> - const char *str;
> -
> - for_each_of_cpu_node(node) {
> - if (of_property_read_string(node, "mmu-type", &str))
> - continue;
> -
> - if (!strncmp(str + 6, "none", 4))
> - continue;
> -
> - if (of_property_read_string(node, "riscv,mmu", &str))
> - continue;
> -
> - if (!strncmp(str + 6, "svpbmt", 6))
> - return true;
> - }
> -
> - return false;
> -}
> -#endif
> -
> static bool __init_or_module cpufeature_svpbmt_check_func(unsigned int stage)
> {
> bool ret = false;
> @@ -319,10 +263,8 @@ static bool __init_or_module cpufeature_svpbmt_check_func(unsigned int stage)
> switch (stage) {
> case RISCV_ALTERNATIVES_EARLY_BOOT:
> return false;
> - case RISCV_ALTERNATIVES_BOOT:
> - return cpufeature_svpbmt_check_fdt();
> default:
> - return cpufeature_svpbmt_check_of();
> + return riscv_isa_extension_available(NULL, SVPBMT);
> }
> #endif
>
> diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
> index c01012f3740d..ec07f991866a 100644
> --- a/arch/riscv/kernel/head.S
> +++ b/arch/riscv/kernel/head.S
> @@ -10,7 +10,6 @@
> #include <asm/thread_info.h>
> #include <asm/page.h>
> #include <asm/pgtable.h>
> -#include <asm/alternative.h>
> #include <asm/csr.h>
> #include <asm/cpu_ops_sbi.h>
> #include <asm/hwcap.h>
> @@ -341,7 +340,6 @@ clear_bss_done:
> call kasan_early_init
> #endif
> /* Start the kernel */
> - call apply_boot_alternatives
> call soc_early_init
> tail start_kernel
>
> diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
> index 339ceb595b38..b4879c942b42 100644
> --- a/arch/riscv/kernel/setup.c
> +++ b/arch/riscv/kernel/setup.c
> @@ -21,6 +21,7 @@
> #include <linux/efi.h>
> #include <linux/crash_dump.h>
>
> +#include <asm/alternative.h>
> #include <asm/cpu_ops.h>
> #include <asm/early_ioremap.h>
> #include <asm/pgtable.h>
> @@ -295,6 +296,7 @@ void __init setup_arch(char **cmdline_p)
> #endif
>
> riscv_fill_hwcap();
> + apply_boot_alternatives();
> }
>
> static int __init topology_init(void)
>
>
>

Looks good to me.

--
Regards,
Atish

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