From: Ard Biesheuvel <ardb@kernel.org>
To: linux-arm-kernel@lists.infradead.org
Cc: Ard Biesheuvel <ardb@kernel.org>, Will Deacon <will@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Marc Zyngier <maz@kernel.org>,
Mark Rutland <mark.rutland@arm.com>
Subject: [PATCH v6 4/6] arm64: head: avoid cache invalidation when entering with the MMU on
Date: Tue, 29 Nov 2022 17:14:16 +0100 [thread overview]
Message-ID: <20221129161418.1968319-5-ardb@kernel.org> (raw)
In-Reply-To: <20221129161418.1968319-1-ardb@kernel.org>
If we enter with the MMU on, there is no need for explicit cache
invalidation for stores to memory, as they will be coherent with the
caches.
Let's take advantage of this, and create the ID map with the MMU still
enabled if that is how we entered, and avoid any cache invalidation
calls in that case.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
arch/arm64/kernel/head.S | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index c3b97f4ae6d769f7..5abf8f9fdd97b673 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -93,9 +93,9 @@ SYM_CODE_START(efi_primary_entry)
SYM_INNER_LABEL(primary_entry, SYM_L_LOCAL)
mov x19, xzr // MMU must be off on bare metal boot
0: bl preserve_boot_args
+ bl create_idmap
bl init_kernel_el // w0=cpu_boot_mode
mov x20, x0
- bl create_idmap
/*
* The following calls CPU setup code, see arch/arm64/mm/proc.S for
@@ -381,12 +381,13 @@ SYM_FUNC_START_LOCAL(create_idmap)
* accesses (MMU disabled), invalidate those tables again to
* remove any speculatively loaded cache lines.
*/
+ cbnz x19, 0f // skip cache invalidation if MMU is on
dmb sy
adrp x0, init_idmap_pg_dir
adrp x1, init_idmap_pg_end
bl dcache_inval_poc
- ret x28
+0: ret x28
SYM_FUNC_END(create_idmap)
SYM_FUNC_START_LOCAL(create_kernel_mapping)
--
2.35.1
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next prev parent reply other threads:[~2022-11-29 16:18 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-29 16:14 [PATCH v6 0/6] arm64: Permit EFI boot with MMU and caches on Ard Biesheuvel
2022-11-29 16:14 ` [PATCH v6 1/6] arm64: head: Move all finalise_el2 calls to after __enable_mmu Ard Biesheuvel
2022-11-29 16:14 ` [PATCH v6 2/6] arm64: kernel: move identity map out of .text mapping Ard Biesheuvel
2022-11-29 16:14 ` [PATCH v6 3/6] arm64: head: record the MMU state at primary entry Ard Biesheuvel
2022-12-01 9:18 ` Ard Biesheuvel
2022-12-01 17:51 ` Will Deacon
2022-11-29 16:14 ` Ard Biesheuvel [this message]
2022-11-29 16:14 ` [PATCH v6 5/6] arm64: head: Clean the ID map and the HYP text to the PoC if needed Ard Biesheuvel
2022-11-29 16:14 ` [PATCH v6 6/6] arm64: lds: reduce effective minimum image alignment to 64k Ard Biesheuvel
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