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From:   Huacai Chen <chenhuacai@kernel.org>
Date:   Tue, 23 Aug 2022 11:11:16 +0800
Message-ID: <CAAhV-H7Wsjf9GAQVkBeu+PKbGOJ5nAxGY=E3zryu_8OK4qtnGA@mail.gmail.com>
Subject: Re: [PATCH V3] LoongArch: Add efistub booting support
To:     Ard Biesheuvel <ardb@kernel.org>
Cc:     Huacai Chen <chenhuacai@loongson.cn>,
        Arnd Bergmann <arnd@arndb.de>, loongarch@lists.linux.dev,
        linux-arch <linux-arch@vger.kernel.org>,
        Xuefeng Li <lixuefeng@loongson.cn>,
        Guo Ren <guoren@kernel.org>, Xuerui Wang <kernel@xen0n.name>,
        Jiaxun Yang <jiaxun.yang@flygoat.com>,
        linux-efi <linux-efi@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Xi Ruoyao <xry111@xry111.site>
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Hi, Ard,

On Tue, Aug 23, 2022 at 2:03 AM Ard Biesheuvel <ardb@kernel.org> wrote:
>
> On Mon, 22 Aug 2022 at 12:44, Ard Biesheuvel <ardb@kernel.org> wrote:
> >
> > On Fri, 19 Aug 2022 at 12:20, Huacai Chen <chenhuacai@loongson.cn> wrote:
> > >
> > > This patch adds efistub booting support, which is the standard UEFI boot
> > > protocol for us to use.
> > >
> > > We use generic efistub, which means we can pass boot information (i.e.,
> > > system table, memory map, kernel command line, initrd) via a light FDT
> > > and drop a lot of non-standard code.
> > >
> > > We use a flat mapping to map the efi runtime in the kernel's address
> > > space. In efi, VA = PA; in kernel, VA = PA + PAGE_OFFSET. As a result,
> > > flat mapping is not identity mapping, SetVirtualAddressMap() is still
> > > needed for the efi runtime.
> > >
> > > Tested-by: Xi Ruoyao <xry111@xry111.site>
> > > Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
> > > ---
> > > V1 --> V2:
> > > 1, Call SetVirtualAddressMap() in stub;
> > > 2, Use core kernel data directly in alloc_screen_info();
> > > 3, Remove the magic number in MS-DOS header;
> > > 4, Disable EFI_GENERIC_STUB_INITRD_CMDLINE_LOADER;
> > > 5, Some other small changes suggested by Ard Biesheuvel.
> > >
> > > V2 --> V3:
> > > 1, Adjust Makefile to adapt zboot;
> > > 2, Introduce EFI_RT_VIRTUAL_OFFSET instead of changing flat_va_mapping.
> > >
> >
> > Thanks for the update.
> >
> > I am going to queue this up in the efi/next tree. However, due to the
> > many changes to arch/loongarch in this patch, conflicts are not
> > unlikely, so I created a signed stable tag for the patch that you can
> > merge into the loongarch arch tree if you want.
> >
> > *However*, you must *not* rebase your tree after merging this tag.
> > Therefore, it is probably best that the merge of this tag appears as
> > the very first change on your PR to Linus for v6.1. Everything after
> > can be rebased at will (assuming there are no other impediments to
> > doing so)
> >
> > You can fetch it and merge it like so:
> >
> > git fetch -t git://git.kernel.org/pub/scm/linux/kernel/git/efi/efi.git
> > git verify-tag efi-loongarch-for-v6.1 # if you like
> > git merge efi-loongarch-for-v6.1
> >
> > and all your other v6.1 changes can go on top.
> >
> > This way, you can resolve conflicts locally without affecting the EFI
> > changes going via the other tree. The EFI stub for LoongArch change
> > will arrive into Linus's tree via whichever tree he pulls first: the
> > LoongArch one or the EFI one.
> >
> > I will rebase my zboot decompressor changes on top of this - I will cc
> > you again, as the LoongArch builds ok but still does not boot.
> >
>
> I have pushed a branch here that includes EFI decompressor support for LoongArch
>
> https://git.kernel.org/pub/scm/linux/kernel/git/ardb/linux.git/log/?h=efi-decompressor-v4
>
> You will need to enable CONFIG_EFI_ZBOOT and build the zImage.efi
> target. The resulting image should be bootable jus tlike the
> vmlinux.efi but for some reason, it produces the crash I reported
> earlier.
>
> Please give it a try, and if you manage to figure out what's wrong
> with my code, please let me know :-)
I will try zboot on my real machine. For the code, I prefer
vmlinuz.efi rather than zImage.efi for LoongArch since it keeps the
naming consistency.

Huacai
>
> Thanks,
> Ard.