RE: [EXT] Re: [PATCH v6 2/2] arm64/crash_core: Export TCR_EL1.T1SZ in vmcoreinfo

From: Kamlakant Patel
Date: Thu Jun 04 2020 - 00:49:38 EST

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Hi Bhupesh,

> -----Original Message-----
> From: Bhupesh Sharma <bhsharma@xxxxxxxxxx>
> Sent: Thursday, June 4, 2020 2:05 AM
> To: Kamlakant Patel <kamlakantp@xxxxxxxxxxx>
> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; x86@xxxxxxxxxx; Mark Rutland
> <mark.rutland@xxxxxxx>; Kazuhito Hagio <k-hagio@xxxxxxxxxxxxx>; Steve
> Capper <steve.capper@xxxxxxx>; Catalin Marinas
> <catalin.marinas@xxxxxxx>; Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>;
> kexec@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; James Morse
> <james.morse@xxxxxxx>; Dave Anderson <anderson@xxxxxxxxxx>;
> bhupesh.linux@xxxxxxxxx; Will Deacon <will@xxxxxxxxxx>; Ganapatrao Kulkarni
> <gkulkarni@xxxxxxxxxxx>
> Subject: [EXT] Re: [PATCH v6 2/2] arm64/crash_core: Export TCR_EL1.T1SZ in
> vmcoreinfo
>
> External Email
>
> ----------------------------------------------------------------------
> Hi Kamlakant,
>
> Many thanks for having a look at the patchset.
>
> On Wed, Jun 3, 2020 at 4:50 PM Kamlakant Patel <kamlakantp@xxxxxxxxxxx>
> wrote:
> >
> > Hi Bhupesh,
> >
> > > -----Original Message-----
> > > From: kexec <kexec-bounces@xxxxxxxxxxxxxxxxxxx> On Behalf Of Bhupesh
> > > Sharma
> > > Sent: Thursday, May 14, 2020 12:23 AM
> > > To: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; x86@xxxxxxxxxx
> > > Cc: Mark Rutland <mark.rutland@xxxxxxx>; Kazuhito Hagio <k-
> > > hagio@xxxxxxxxxxxxx>; Steve Capper <steve.capper@xxxxxxx>; Catalin
> > > Marinas <catalin.marinas@xxxxxxx>; bhsharma@xxxxxxxxxx; Ard
> > > Biesheuvel <ard.biesheuvel@xxxxxxxxxx>; kexec@xxxxxxxxxxxxxxxxxxx;
> > > linux- kernel@xxxxxxxxxxxxxxx; James Morse <james.morse@xxxxxxx>;
> > > Dave Anderson <anderson@xxxxxxxxxx>; bhupesh.linux@xxxxxxxxx; Will
> > > Deacon <will@xxxxxxxxxx>
> > > Subject: [PATCH v6 2/2] arm64/crash_core: Export TCR_EL1.T1SZ in
> > > vmcoreinfo
> > >
> > > vabits_actual variable on arm64 indicates the actual VA space size,
> > > and allows a single binary to support both 48-bit and 52-bit VA spaces.
> > >
> > > If the ARMv8.2-LVA optional feature is present, and we are running
> > > with a 64KB page size; then it is possible to use 52-bits of address
> > > space for both userspace and kernel addresses. However, any kernel
> > > binary that supports 52-bit must also be able to fall back to 48-bit
> > > at early boot time if the hardware feature is not present.
> > >
> > > Since TCR_EL1.T1SZ indicates the size offset of the memory region
> > > addressed by
> > > TTBR1_EL1 (and hence can be used for determining the vabits_actual
> > > value) it makes more sense to export the same in vmcoreinfo rather
> > > than vabits_actual variable, as the name of the variable can change
> > > in future kernel versions, but the architectural constructs like
> > > TCR_EL1.T1SZ can be used better to indicate intended specific fields to user-
> space.
> > >
> > > User-space utilities like makedumpfile and crash-utility, need to
> > > read this value from vmcoreinfo for determining if a virtual address lies in the
> linear map range.
> > >
> > > While at it also add documentation for TCR_EL1.T1SZ variable being
> > > added to vmcoreinfo.
> > >
> > > It indicates the size offset of the memory region addressed by
> > > TTBR1_EL1
> > >
> > > Cc: James Morse <james.morse@xxxxxxx>
> > > Cc: Mark Rutland <mark.rutland@xxxxxxx>
> > > Cc: Will Deacon <will@xxxxxxxxxx>
> > > Cc: Steve Capper <steve.capper@xxxxxxx>
> > > Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> > > Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> > > Cc: Dave Anderson <anderson@xxxxxxxxxx>
> > > Cc: Kazuhito Hagio <k-hagio@xxxxxxxxxxxxx>
> > > Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> > > Cc: linux-kernel@xxxxxxxxxxxxxxx
> > > Cc: kexec@xxxxxxxxxxxxxxxxxxx
> > > Tested-by: John Donnelly <john.p.donnelly@xxxxxxxxxx>
> > > Signed-off-by: Bhupesh Sharma <bhsharma@xxxxxxxxxx>
> > > ---
> > > Documentation/admin-guide/kdump/vmcoreinfo.rst | 11 +++++++++++
> > > arch/arm64/include/asm/pgtable-hwdef.h | 1 +
> > > arch/arm64/kernel/crash_core.c | 10 ++++++++++
> > > 3 files changed, 22 insertions(+)
> > >
> > > diff --git a/Documentation/admin-guide/kdump/vmcoreinfo.rst
> > > b/Documentation/admin-guide/kdump/vmcoreinfo.rst
> > > index 2a632020f809..2baad0bfb09d 100644
> > > --- a/Documentation/admin-guide/kdump/vmcoreinfo.rst
> > > +++ b/Documentation/admin-guide/kdump/vmcoreinfo.rst
> > > @@ -404,6 +404,17 @@ KERNELPACMASK
> > > The mask to extract the Pointer Authentication Code from a kernel
> > > virtual address.
> > >
> > > +TCR_EL1.T1SZ
> > > +------------
> > > +
> > > +Indicates the size offset of the memory region addressed by TTBR1_EL1.
> > > +The region size is 2^(64-T1SZ) bytes.
> > > +
> > > +TTBR1_EL1 is the table base address register specified by ARMv8-A
> > > +architecture which is used to lookup the page-tables for the
> > > +Virtual addresses in the higher VA range (refer to ARMv8 ARM
> > > +document for more details).
> > > +
> > > arm
> > > ===
> > >
> > > diff --git a/arch/arm64/include/asm/pgtable-hwdef.h
> > > b/arch/arm64/include/asm/pgtable-hwdef.h
> > > index 6bf5e650da78..a1861af97ac9 100644
> > > --- a/arch/arm64/include/asm/pgtable-hwdef.h
> > > +++ b/arch/arm64/include/asm/pgtable-hwdef.h
> > > @@ -216,6 +216,7 @@
> > > #define TCR_TxSZ(x) (TCR_T0SZ(x) | TCR_T1SZ(x))
> > > #define TCR_TxSZ_WIDTH 6
> > > #define TCR_T0SZ_MASK (((UL(1) << TCR_TxSZ_WIDTH) - 1) <<
> > > TCR_T0SZ_OFFSET)
> > > +#define TCR_T1SZ_MASK (((UL(1) << TCR_TxSZ_WIDTH) - 1) <<
> > > TCR_T1SZ_OFFSET)
> > >
> > > #define TCR_EPD0_SHIFT 7
> > > #define TCR_EPD0_MASK (UL(1) << TCR_EPD0_SHIFT)
> > > diff --git a/arch/arm64/kernel/crash_core.c
> > > b/arch/arm64/kernel/crash_core.c index 1f646b07e3e9..314391a156ee
> > > 100644
> > > --- a/arch/arm64/kernel/crash_core.c
> > > +++ b/arch/arm64/kernel/crash_core.c
> > > @@ -7,6 +7,14 @@
> > > #include <linux/crash_core.h>
> > > #include <asm/cpufeature.h>
> > > #include <asm/memory.h>
> > > +#include <asm/pgtable-hwdef.h>
> > > +
> > > +static inline u64 get_tcr_el1_t1sz(void);
> > > +
> > > +static inline u64 get_tcr_el1_t1sz(void) {
> > > + return (read_sysreg(tcr_el1) & TCR_T1SZ_MASK) >>
> > > +TCR_T1SZ_OFFSET; }
> > >
> > > void arch_crash_save_vmcoreinfo(void) { @@ -16,6 +24,8 @@ void
> > > arch_crash_save_vmcoreinfo(void)
> > > kimage_voffset);
> > > vmcoreinfo_append_str("NUMBER(PHYS_OFFSET)=0x%llx\n",
> > > PHYS_OFFSET);
> > > + vmcoreinfo_append_str("NUMBER(TCR_EL1_T1SZ)=0x%llx\n",
> > > + get_tcr_el1_t1sz());
> > I tested this patch on top of upstream kernel v5.7 and I am getting "crash:
> cannot determine VA_BITS_ACTUAL" error with crash tool.
> > I looked into crash-utility source and it is expecting tcr_el1_t1sz not
> TCR_EL1_T1SZ.
> > Could you please check.
>
> Indeed. As per James comments on the v5 (see [1]) where he suggested
> converting ttcr_el1_t1sz into TCR_EL1_T1SZ, I made the change in v6
> accordingly.
>
> This time I haven't sent out the v6 userspace changes
> (makedumpfile/crash-utility) upstream first, since we are waiting for kernel
> changes to be accepted first, as we have seen in the past that while the
> userspace patches have been accepted, the kernel patches required a respin
> cycle, thus leading to inconsistencies, as you also pointed out with crash-utility.
>
> If you want, for your local testing, I can share my github branch where I have
> kept the crash-utility v6 patchset ready. Please let me know.
>
> [1]. https://urldefense.proofpoint.com/v2/url?u=https-
> 3A__lore.kernel.org_linuxppc-2Ddev_63d6e63c-2D7218-2Dd2dd-2D8767-
> 2D4464be83603f-
> 40arm.com_&d=DwIBaQ&c=nKjWec2b6R0mOyPaz7xtfQ&r=XecQZQJWhG6-
> mN8sWxffFOgUXg4irGP3Sjuy6RxdacQ&m=ijR8vEafG_QGTKYX2oI-
> SvfFsY4pPou6tvtrnxRoloo&s=zJmo3qbm2XfnKbrUqJPNN5o6PJqER9OzltwgS4aTa
> -k&e=
Thanks for clarifying.
I made userspace changes accordingly and tested and it works fine. We will be wait for your userspace patch.

Tested-by: Kamlakant Patel <kamlakantp@xxxxxxxxxxx>

Thanks,
Kamlakant Patel
>
> Thanks,
> Bhupesh
>
>
> >
> > Thanks,
> > Kamlakant Patel
> > > vmcoreinfo_append_str("KERNELOFFSET=%lx\n", kaslr_offset());
> > > vmcoreinfo_append_str("NUMBER(KERNELPACMASK)=0x%llx\n",
> > >
> > > system_supports_address_auth() ?
> > > --
> > > 2.7.4
> > >
> > >
> > > _______________________________________________
> > > kexec mailing list
> > > kexec@xxxxxxxxxxxxxxxxxxx
> > > https://urldefense.proofpoint.com/v2/url?u=http-
> > > 3A__lists.infradead.org_mailman_listinfo_kexec&d=DwICAg&c=nKjWec2b6R
> > > 0m
> > > OyPaz7xtfQ&r=XecQZQJWhG6-
> > >
> mN8sWxffFOgUXg4irGP3Sjuy6RxdacQ&m=oeLdIVaWScimdfEc4dNhRI0tT24IgzG
> > > 7LkpAE5P11JQ&s=LLjHpz349DuDtORX4xywCxzbGUOagoq4JXosStycqI4&e=
> >

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Previous message: Christian Hewitt: "[PATCH] soc: amlogic: meson-gx-socinfo: Fix S905X3 ID"
In reply to: Bhupesh Sharma: "Re: [PATCH v6 2/2] arm64/crash_core: Export TCR_EL1.T1SZ in vmcoreinfo"
Next in thread: Will Deacon: "Re: [PATCH v6 2/2] arm64/crash_core: Export TCR_EL1.T1SZ in vmcoreinfo"
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