[PATCH 8/8] KVM: arm64: Avoid repetitive stack access on host EL1 to EL2 exception

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From: Marc Zyngier <maz@kernel.org>
To: linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org
Cc: James Morse <james.morse@arm.com>,
	Julien Thierry <julien.thierry.kdev@gmail.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Andrew Scull <ascull@google.com>, Will Deacon <will@kernel.org>,
	Quentin Perret <qperret@google.com>,
	kernel-team@android.com
Subject: [PATCH 8/8] KVM: arm64: Avoid repetitive stack access on host EL1 to EL2 exception
Date: Mon, 26 Oct 2020 09:51:16 +0000	[thread overview]
Message-ID: <20201026095116.72051-9-maz@kernel.org> (raw)
In-Reply-To: <20201026095116.72051-1-maz@kernel.org>

Registers x0/x1 get repeateadly pushed and poped during a host
HVC call. Instead, leave the registers on the stack, saving
a store instruction on the fast path for an add on the slow path.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/kvm/hyp/nvhe/host.S | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/host.S b/arch/arm64/kvm/hyp/nvhe/host.S
index e2d316d13180..7b69f9ff8da0 100644
--- a/arch/arm64/kvm/hyp/nvhe/host.S
+++ b/arch/arm64/kvm/hyp/nvhe/host.S
@@ -13,8 +13,6 @@
 	.text
 
 SYM_FUNC_START(__host_exit)
-	stp	x0, x1, [sp, #-16]!
-
 	get_host_ctxt	x0, x1
 
 	/* Store the host regs x2 and x3 */
@@ -99,13 +97,14 @@ SYM_FUNC_END(__hyp_do_panic)
 	mrs	x0, esr_el2
 	lsr	x0, x0, #ESR_ELx_EC_SHIFT
 	cmp	x0, #ESR_ELx_EC_HVC64
-	ldp	x0, x1, [sp], #16
+	ldp	x0, x1, [sp]		// Don't fixup the stack yet
 	b.ne	__host_exit
 
 	/* Check for a stub HVC call */
 	cmp	x0, #HVC_STUB_HCALL_NR
 	b.hs	__host_exit
 
+	add	sp, sp, #16
 	/*
 	 * Compute the idmap address of __kvm_handle_stub_hvc and
 	 * jump there. Since we use kimage_voffset, do not use the
-- 
2.28.0

WARNING: multiple messages have this Message-ID (diff)

From: Marc Zyngier <maz@kernel.org>
To: linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org
Cc: kernel-team@android.com, Will Deacon <will@kernel.org>
Subject: [PATCH 8/8] KVM: arm64: Avoid repetitive stack access on host EL1 to EL2 exception
Date: Mon, 26 Oct 2020 09:51:16 +0000	[thread overview]
Message-ID: <20201026095116.72051-9-maz@kernel.org> (raw)
In-Reply-To: <20201026095116.72051-1-maz@kernel.org>

Registers x0/x1 get repeateadly pushed and poped during a host
HVC call. Instead, leave the registers on the stack, saving
a store instruction on the fast path for an add on the slow path.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/kvm/hyp/nvhe/host.S | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/host.S b/arch/arm64/kvm/hyp/nvhe/host.S
index e2d316d13180..7b69f9ff8da0 100644
--- a/arch/arm64/kvm/hyp/nvhe/host.S
+++ b/arch/arm64/kvm/hyp/nvhe/host.S
@@ -13,8 +13,6 @@
 	.text
 
 SYM_FUNC_START(__host_exit)
-	stp	x0, x1, [sp, #-16]!
-
 	get_host_ctxt	x0, x1
 
 	/* Store the host regs x2 and x3 */
@@ -99,13 +97,14 @@ SYM_FUNC_END(__hyp_do_panic)
 	mrs	x0, esr_el2
 	lsr	x0, x0, #ESR_ELx_EC_SHIFT
 	cmp	x0, #ESR_ELx_EC_HVC64
-	ldp	x0, x1, [sp], #16
+	ldp	x0, x1, [sp]		// Don't fixup the stack yet
 	b.ne	__host_exit
 
 	/* Check for a stub HVC call */
 	cmp	x0, #HVC_STUB_HCALL_NR
 	b.hs	__host_exit
 
+	add	sp, sp, #16
 	/*
 	 * Compute the idmap address of __kvm_handle_stub_hvc and
 	 * jump there. Since we use kimage_voffset, do not use the
-- 
2.28.0

_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

WARNING: multiple messages have this Message-ID (diff)

From: Marc Zyngier <maz@kernel.org>
To: linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org
Cc: Quentin Perret <qperret@google.com>,
	kernel-team@android.com,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	James Morse <james.morse@arm.com>,
	Andrew Scull <ascull@google.com>, Will Deacon <will@kernel.org>,
	Julien Thierry <julien.thierry.kdev@gmail.com>
Subject: [PATCH 8/8] KVM: arm64: Avoid repetitive stack access on host EL1 to EL2 exception
Date: Mon, 26 Oct 2020 09:51:16 +0000	[thread overview]
Message-ID: <20201026095116.72051-9-maz@kernel.org> (raw)
In-Reply-To: <20201026095116.72051-1-maz@kernel.org>

Registers x0/x1 get repeateadly pushed and poped during a host
HVC call. Instead, leave the registers on the stack, saving
a store instruction on the fast path for an add on the slow path.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/kvm/hyp/nvhe/host.S | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/host.S b/arch/arm64/kvm/hyp/nvhe/host.S
index e2d316d13180..7b69f9ff8da0 100644
--- a/arch/arm64/kvm/hyp/nvhe/host.S
+++ b/arch/arm64/kvm/hyp/nvhe/host.S
@@ -13,8 +13,6 @@
 	.text
 
 SYM_FUNC_START(__host_exit)
-	stp	x0, x1, [sp, #-16]!
-
 	get_host_ctxt	x0, x1
 
 	/* Store the host regs x2 and x3 */
@@ -99,13 +97,14 @@ SYM_FUNC_END(__hyp_do_panic)
 	mrs	x0, esr_el2
 	lsr	x0, x0, #ESR_ELx_EC_SHIFT
 	cmp	x0, #ESR_ELx_EC_HVC64
-	ldp	x0, x1, [sp], #16
+	ldp	x0, x1, [sp]		// Don't fixup the stack yet
 	b.ne	__host_exit
 
 	/* Check for a stub HVC call */
 	cmp	x0, #HVC_STUB_HCALL_NR
 	b.hs	__host_exit
 
+	add	sp, sp, #16
 	/*
 	 * Compute the idmap address of __kvm_handle_stub_hvc and
 	 * jump there. Since we use kimage_voffset, do not use the
-- 
2.28.0


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

next prev parent reply	other threads:[~2020-10-26 10:09 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-26  9:51 [PATCH 0/8] KVM: arm64: Host EL2 entry improvements Marc Zyngier
2020-10-26  9:51 ` Marc Zyngier
2020-10-26  9:51 ` Marc Zyngier
2020-10-26  9:51 ` [PATCH 1/8] KVM: arm64: Don't corrupt tpidr_el2 on failed HVC call Marc Zyngier
2020-10-26  9:51   ` Marc Zyngier
2020-10-26  9:51   ` Marc Zyngier
2020-10-26 14:36   ` Quentin Perret
2020-10-26 14:36     ` Quentin Perret
2020-10-26 14:36     ` Quentin Perret
2020-10-26  9:51 ` [PATCH 2/8] KVM: arm64: Remove leftover kern_hyp_va() in nVHE TLB invalidation Marc Zyngier
2020-10-26  9:51   ` Marc Zyngier
2020-10-26  9:51   ` Marc Zyngier
2020-11-02 13:30   ` Alexandru Elisei
2020-11-02 13:30     ` Alexandru Elisei
2020-11-02 13:30     ` Alexandru Elisei
2020-10-26  9:51 ` [PATCH 3/8] KVM: arm64: Drop useless PAN setting on host EL1 to EL2 transition Marc Zyngier
2020-10-26  9:51   ` Marc Zyngier
2020-10-26  9:51   ` Marc Zyngier
2020-10-26 10:48   ` Vladimir Murzin
2020-10-26 10:48     ` Vladimir Murzin
2020-10-26 10:48     ` Vladimir Murzin
2020-10-26  9:51 ` [PATCH 4/8] KVM: arm64: Add kimg_hyp_va() helper Marc Zyngier
2020-10-26  9:51   ` Marc Zyngier
2020-10-26  9:51   ` Marc Zyngier
2020-10-26  9:51 ` [PATCH 5/8] KVM: arm64: Turn host HVC handling into a dispatch table Marc Zyngier
2020-10-26  9:51   ` Marc Zyngier
2020-10-26  9:51   ` Marc Zyngier
2020-11-02 14:19   ` Alexandru Elisei
2020-11-02 14:19     ` Alexandru Elisei
2020-11-02 14:19     ` Alexandru Elisei
2020-10-26  9:51 ` [PATCH 6/8] KVM: arm64: Patch kimage_voffset instead of loading the EL1 value Marc Zyngier
2020-10-26  9:51   ` Marc Zyngier
2020-10-26  9:51   ` Marc Zyngier
2020-10-26  9:51 ` [PATCH 7/8] KVM: arm64: Simplify __kvm_enable_ssbs() Marc Zyngier
2020-10-26  9:51   ` Marc Zyngier
2020-10-26  9:51   ` Marc Zyngier
2020-11-02 15:30   ` Alexandru Elisei
2020-11-02 15:30     ` Alexandru Elisei
2020-11-02 15:30     ` Alexandru Elisei
2020-10-26  9:51 ` Marc Zyngier [this message]
2020-10-26  9:51   ` [PATCH 8/8] KVM: arm64: Avoid repetitive stack access on host EL1 to EL2 exception Marc Zyngier
2020-10-26  9:51   ` Marc Zyngier
2020-11-02 16:28   ` Alexandru Elisei
2020-11-02 16:28     ` Alexandru Elisei
2020-11-02 16:28     ` Alexandru Elisei

find likely ancestor, descendant, or conflicting patches for this message:
dfblob:e2d316d1318 dfblob:e2d316d1318 dfblob:e2d316d1318
dfblob:7b69f9ff8da dfblob:7b69f9ff8da dfblob:7b69f9ff8da
	(help)

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