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>,
ndesaulniers@google.com
Subject: [PATCH v2 5/5] KVM: arm64: Avoid repetitive stack access on host EL1 to EL2 exception
Date: Mon, 9 Nov 2020 17:59:23 +0000 [thread overview]
Message-ID: <20201109175923.445945-6-maz@kernel.org> (raw)
In-Reply-To: <20201109175923.445945-1-maz@kernel.org>
Registers x0/x1 get repeateadly pushed and poped during a host
HVC call. Instead, leave the registers on the stack, trading
a store instruction on the fast path for an add on the slow path.
Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
arch/arm64/kvm/hyp/nvhe/host.S | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/arm64/kvm/hyp/nvhe/host.S b/arch/arm64/kvm/hyp/nvhe/host.S
index 4e207c1c5126..fe2740b224cf 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 +97,15 @@ 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
b.ne __host_exit
+ ldp x0, x1, [sp] // Don't fixup the stack yet
+
/* 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: kernel-team@android.com,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Will Deacon <will@kernel.org>,
Quentin Perret <qperret@google.com>,
ndesaulniers@google.com, James Morse <james.morse@arm.com>,
Andrew Scull <ascull@google.com>,
dbrazdil@google.com, Alexandru Elisei <alexandru.elisei@arm.com>,
Julien Thierry <julien.thierry.kdev@gmail.com>
Subject: [PATCH v2 5/5] KVM: arm64: Avoid repetitive stack access on host EL1 to EL2 exception
Date: Mon, 9 Nov 2020 17:59:23 +0000 [thread overview]
Message-ID: <20201109175923.445945-6-maz@kernel.org> (raw)
In-Reply-To: <20201109175923.445945-1-maz@kernel.org>
Registers x0/x1 get repeateadly pushed and poped during a host
HVC call. Instead, leave the registers on the stack, trading
a store instruction on the fast path for an add on the slow path.
Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
arch/arm64/kvm/hyp/nvhe/host.S | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/arm64/kvm/hyp/nvhe/host.S b/arch/arm64/kvm/hyp/nvhe/host.S
index 4e207c1c5126..fe2740b224cf 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 +97,15 @@ 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
b.ne __host_exit
+ ldp x0, x1, [sp] // Don't fixup the stack yet
+
/* 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
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: James Morse <james.morse@arm.com>,
Julien Thierry <julien.thierry.kdev@gmail.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Alexandru Elisei <alexandru.elisei@arm.com>,
Andrew Scull <ascull@google.com>, Will Deacon <will@kernel.org>,
Quentin Perret <qperret@google.com>,
ndesaulniers@google.com, dbrazdil@google.com,
kernel-team@android.com
Subject: [PATCH v2 5/5] KVM: arm64: Avoid repetitive stack access on host EL1 to EL2 exception
Date: Mon, 9 Nov 2020 17:59:23 +0000 [thread overview]
Message-ID: <20201109175923.445945-6-maz@kernel.org> (raw)
In-Reply-To: <20201109175923.445945-1-maz@kernel.org>
Registers x0/x1 get repeateadly pushed and poped during a host
HVC call. Instead, leave the registers on the stack, trading
a store instruction on the fast path for an add on the slow path.
Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
arch/arm64/kvm/hyp/nvhe/host.S | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/arm64/kvm/hyp/nvhe/host.S b/arch/arm64/kvm/hyp/nvhe/host.S
index 4e207c1c5126..fe2740b224cf 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 +97,15 @@ 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
b.ne __host_exit
+ ldp x0, x1, [sp] // Don't fixup the stack yet
+
/* 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
next prev parent reply other threads:[~2020-11-09 17:59 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-09 17:59 [PATCH v2 0/5] KVM: arm64: Host EL2 entry improvements Marc Zyngier
2020-11-09 17:59 ` Marc Zyngier
2020-11-09 17:59 ` Marc Zyngier
2020-11-09 17:59 ` [PATCH v2 1/5] KVM: arm64: Add kimg_hyp_va() helper Marc Zyngier
2020-11-09 17:59 ` Marc Zyngier
2020-11-09 17:59 ` Marc Zyngier
2020-11-09 17:59 ` [PATCH v2 2/5] KVM: arm64: Turn host HVC handling into a dispatch table Marc Zyngier
2020-11-09 17:59 ` Marc Zyngier
2020-11-09 17:59 ` Marc Zyngier
2020-11-09 17:59 ` [PATCH v2 3/5] KVM: arm64: Patch kimage_voffset instead of loading the EL1 value Marc Zyngier
2020-11-09 17:59 ` Marc Zyngier
2020-11-09 17:59 ` Marc Zyngier
2020-11-19 11:14 ` David Brazdil
2020-11-19 11:14 ` David Brazdil
2020-11-19 11:14 ` David Brazdil
2020-11-20 11:26 ` Marc Zyngier
2020-11-20 11:26 ` Marc Zyngier
2020-11-20 11:26 ` Marc Zyngier
2020-11-09 17:59 ` [PATCH v2 4/5] KVM: arm64: Simplify __kvm_enable_ssbs() Marc Zyngier
2020-11-09 17:59 ` Marc Zyngier
2020-11-09 17:59 ` Marc Zyngier
2020-11-09 17:59 ` Marc Zyngier [this message]
2020-11-09 17:59 ` [PATCH v2 5/5] KVM: arm64: Avoid repetitive stack access on host EL1 to EL2 exception Marc Zyngier
2020-11-09 17:59 ` Marc Zyngier
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