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    SubjectRe: [PATCH v7 0/5] LoongArch: Support toolchain with new relocation types
    Hi, Ruoyao,

    On Tue, Sep 6, 2022 at 8:32 AM Xi Ruoyao <xry111@xry111.site> wrote:
    >
    > On Thu, 2022-09-01 at 10:17 +0800, Huacai Chen wrote:
    >
    > > Now all global variable accesses are via got, I think the performance
    > > may be much worse than before when we didn't use explicit-relocs.
    > > I don't know whether "a new code model" or your "(1)(2)(3)" is easier
    > > to implement, but I think it is better to solve the performance issue
    > > before 6.1-rc1.
    >
    > Hi Huacai,
    >
    > We've added a GCC option for this at https://gcc.gnu.org/r13-2433. On
    > the kernel side we need a one-line change:
    >
    > diff --git a/arch/loongarch/Makefile b/arch/loongarch/Makefile
    > index 92c4a52c4c3e..69b39ba3a09d 100644
    > --- a/arch/loongarch/Makefile
    > +++ b/arch/loongarch/Makefile
    > @@ -54,6 +54,7 @@ LDFLAGS_vmlinux += -G0 -static -n -nostdlib
    > # upgrade the compiler or downgrade the assembler.
    > ifdef CONFIG_AS_HAS_EXPLICIT_RELOCS
    > cflags-y += -mexplicit-relocs
    > +KBUILD_CFLAGS_KERNEL += -mdirect-extern-access
    > else
    > cflags-y += $(call cc-option,-mno-explicit-relocs)
    > KBUILD_AFLAGS_KERNEL += -Wa,-mla-global-with-pcrel
    >
    > And we also need a one-line change in the EFI stub patch (under review):
    >
    > diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
    > index 8931ed24379e..8c1225b92492 100644
    > --- a/drivers/firmware/efi/libstub/Makefile
    > +++ b/drivers/firmware/efi/libstub/Makefile
    > @@ -27,7 +27,7 @@ cflags-$(CONFIG_ARM) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \
    > cflags-$(CONFIG_RISCV) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \
    > -fpic
    > cflags-$(CONFIG_LOONGARCH) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \
    > - -fpic
    > + -fpie
    >
    > cflags-$(CONFIG_EFI_GENERIC_STUB) += -I$(srctree)/scripts/dtc/libfdt
    >
    > (Some explanation: -fpic does not only mean "generate position-
    > independent code", but "generate position-independent code *suitable for
    > use in a shared library*". On LoongArch -mdirect-extern-access cannot
    > work for a shared library so the "-fpic -mdirect-extern-access"
    > combination is rejected deliberately.)
    >
    > Not sure how to submit these changes properly... Do you prefer me to
    > send V8 of this series or a single patch on top of your tree on GitHub?
    Don't need V8, I will squash it into the previous patch myself. But
    can we keep efistub as is?

    Huacai
    >
    > --
    > Xi Ruoyao <xry111@xry111.site>
    > School of Aerospace Science and Technology, Xidian University
    >

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