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;
> }
>
>
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next prev 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
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