From: Alexandru Elisei <alexandru.elisei@arm.com>
To: drjones@redhat.com, kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu
Cc: andre.przywara@arm.com
Subject: [kvm-unit-tests PATCH v2 1/6] arm64: Remove unnecessary ISB when writing to SPSel
Date: Mon, 22 Mar 2021 15:06:36 +0000 [thread overview]
Message-ID: <20210322150641.58878-2-alexandru.elisei@arm.com> (raw)
In-Reply-To: <20210322150641.58878-1-alexandru.elisei@arm.com>
Software can use the SPSel operand to write directly to PSTATE.SP.
According to ARM DDI 0487F.b, page D1-2332, writes to PSTATE are
self-synchronizing and no ISB is needed:
"Writes to the PSTATE fields have side-effects on various aspects of the PE
operation. All of these side-effects are guaranteed:
- Not to be visible to earlier instructions in the execution stream.
- To be visible to later instructions in the execution stream."
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
---
arm/cstart64.S | 1 -
1 file changed, 1 deletion(-)
diff --git a/arm/cstart64.S b/arm/cstart64.S
index 0428014aa58a..fc1930bcdb53 100644
--- a/arm/cstart64.S
+++ b/arm/cstart64.S
@@ -54,7 +54,6 @@ start:
/* set up stack */
mov x4, #1
msr spsel, x4
- isb
adrp x4, stackptr
add sp, x4, :lo12:stackptr
--
2.31.0
next prev parent reply other threads:[~2021-03-22 15:07 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-22 15:06 [kvm-unit-tests PATCH v2 0/6] Misc assembly fixes and cleanups Alexandru Elisei
2021-03-22 15:06 ` Alexandru Elisei [this message]
2021-03-22 15:06 ` [kvm-unit-tests PATCH v2 2/6] arm/arm64: Remove dcache_line_size global variable Alexandru Elisei
2021-03-23 16:32 ` Andre Przywara
2021-03-22 15:06 ` [kvm-unit-tests PATCH v2 3/6] arm/arm64: Remove unnecessary ISB when doing dcache maintenance Alexandru Elisei
2021-03-22 15:06 ` [kvm-unit-tests PATCH v2 4/6] lib: arm64: Consolidate register definitions to sysreg.h Alexandru Elisei
2021-03-22 15:06 ` [kvm-unit-tests PATCH v2 5/6] arm64: Configure SCTLR_EL1 at boot Alexandru Elisei
2021-03-22 15:06 ` [kvm-unit-tests PATCH v2 6/6] arm64: Disable TTBR1_EL1 translation table walks Alexandru Elisei
2021-03-25 15:31 ` [kvm-unit-tests PATCH v2 0/6] Misc assembly fixes and cleanups Andrew Jones
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