linux-arm-kernel.lists.infradead.org archive mirror
 help / color / mirror / Atom feed
From: Yicong Yang <yangyicong@huawei.com>
To: Ard Biesheuvel <ardb@kernel.org>, <linux-efi@vger.kernel.org>
Cc: <yangyicong@hisilicon.com>,
	<linux-arm-kernel@lists.infradead.org>, <mark.rutland@arm.com>,
	<probinson@gmail.com>, <andersson@kernel.org>,
	<catalin.marinas@arm.com>, <will@kernel.org>,
	Linuxarm <linuxarm@huawei.com>
Subject: Re: [PATCH] efi/libstub: arm64: avoid SetVirtualAddressMap() when possible
Date: Wed, 19 Oct 2022 11:24:03 +0800	[thread overview]
Message-ID: <56877644-8173-d2ed-ed00-7973734a3698@huawei.com> (raw)
In-Reply-To: <20220916101843.495879-1-ardb@kernel.org>

Hi Ard,

After entering 6.1-rc1 the efi runtime services is not working on my platform:

[    0.054039] Remapping and enabling EFI services.
[    0.054043] UEFI virtual mapping missing or invalid -- runtime services will not be available

Not sure this patch is the root cause since I see some refactor of efi codes in 6.1-rc1,
but simply reverting this make EFI runtime services works again. Tested on HiSilicon's
Kunpeng 920 arm64 server using 48 bit VA address:

CONFIG_ARM64_VA_BITS_48=y
CONFIG_ARM64_VA_BITS=48

Thanks.

On 2022/9/16 18:18, Ard Biesheuvel wrote:
> EFI's SetVirtualAddressMap() runtime service is a horrid hack that we'd
> like to avoid using, if possible. For 64-bit architectures such as
> arm64, the user and kernel mappings are entirely disjoint, and given
> that we use the user region for mapping the UEFI runtime regions when
> running under the OS, we don't rely on SetVirtualAddressMap() in the
> conventional way, i.e., to permit kernel mappings of the OS to coexist
> with kernel region mappings of the firmware regions. This means that, in
> principle, we should be able to avoid SetVirtualAddressMap() altogether,
> and simply use the 1:1 mapping that UEFI uses at boot time. (Note that
> omitting SetVirtualAddressMap() is explicitly permitted by the UEFI
> spec).
> 
> However, there is a corner case on arm64, which, if configured for
> 3-level paging (or 2-level paging when using 64k pages), may not be able
> to cover the entire range of firmware mappings (which might contain both
> memory and MMIO peripheral mappings).
> 
> So let's avoid SetVirtualAddressMap() on arm64, but only if the VA space
> is guaranteed to be of sufficient size.
> 
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> ---
>  drivers/firmware/efi/libstub/arm64-stub.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/firmware/efi/libstub/arm64-stub.c b/drivers/firmware/efi/libstub/arm64-stub.c
> index cd3bea25c762..4fff6c32899e 100644
> --- a/drivers/firmware/efi/libstub/arm64-stub.c
> +++ b/drivers/firmware/efi/libstub/arm64-stub.c
> @@ -31,6 +31,15 @@ efi_status_t check_platform_features(void)
>  			efi_err("This 16 KB granular kernel is not supported by your CPU\n");
>  		return EFI_UNSUPPORTED;
>  	}
> +
> +	/*
> +	 * If we have 48 bits of VA space for TTBR0 mappings, we can map the
> +	 * UEFI runtime regions 1:1 and so calling SetVirtualAddressMap() is
> +	 * unnecessary.
> +	 */
> +	if (VA_BITS_MIN >= 48)
> +		efi_novamap = true;
> +
>  	return EFI_SUCCESS;
>  }
>  
> 

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  parent reply	other threads:[~2022-10-19  3:25 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-16 10:18 [PATCH] efi/libstub: arm64: avoid SetVirtualAddressMap() when possible Ard Biesheuvel
2022-09-16 10:20 ` Ard Biesheuvel
2022-10-19  3:24 ` Yicong Yang [this message]
2022-10-20 12:39   ` Thorsten Leemhuis
2022-10-20 13:04     ` Ard Biesheuvel
2022-10-21  1:59       ` Yicong Yang
2022-10-23 14:58     ` [PATCH] efi/libstub: arm64: avoid SetVirtualAddressMap() when possible #forregzbot Thorsten Leemhuis

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=56877644-8173-d2ed-ed00-7973734a3698@huawei.com \
    --to=yangyicong@huawei.com \
    --cc=andersson@kernel.org \
    --cc=ardb@kernel.org \
    --cc=catalin.marinas@arm.com \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-efi@vger.kernel.org \
    --cc=linuxarm@huawei.com \
    --cc=mark.rutland@arm.com \
    --cc=probinson@gmail.com \
    --cc=will@kernel.org \
    --cc=yangyicong@hisilicon.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).