From: Marc Zyngier <marc.zyngier@arm.com>
To: Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Christoffer Dall <christoffer.dall@linaro.org>
Cc: linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
kvmarm@lists.cs.columbia.edu
Subject: [PATCH v3 22/23] arm64: VHE: Add support for running Linux in EL2 mode
Date: Wed, 3 Feb 2016 18:00:15 +0000 [thread overview]
Message-ID: <1454522416-6874-23-git-send-email-marc.zyngier@arm.com> (raw)
In-Reply-To: <1454522416-6874-1-git-send-email-marc.zyngier@arm.com>
With ARMv8.1 VHE, the architecture is able to (almost) transparently
run the kernel at EL2, despite being written for EL1.
This patch takes care of the "almost" part, mostly preventing the kernel
from dropping from EL2 to EL1, and setting up the HYP configuration.
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
arch/arm64/Kconfig | 13 +++++++++++++
arch/arm64/kernel/head.S | 28 +++++++++++++++++++++++++++-
2 files changed, 40 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 8cc6228..cf118d9 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -750,6 +750,19 @@ config ARM64_LSE_ATOMICS
not support these instructions and requires the kernel to be
built with binutils >= 2.25.
+config ARM64_VHE
+ bool "Enable support for Virtualization Host Extensions (VHE)"
+ default y
+ help
+ Virtualization Host Extensions (VHE) allow the kernel to run
+ directly at EL2 (instead of EL1) on processors that support
+ it. This leads to better performance for KVM, as they reduce
+ the cost of the world switch.
+
+ Selecting this option allows the VHE feature to be detected
+ at runtime, and does not affect processors that do not
+ implement this feature.
+
endmenu
endmenu
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 917d981..6f2f377 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -30,6 +30,7 @@
#include <asm/cache.h>
#include <asm/cputype.h>
#include <asm/kernel-pgtable.h>
+#include <asm/kvm_arm.h>
#include <asm/memory.h>
#include <asm/pgtable-hwdef.h>
#include <asm/pgtable.h>
@@ -464,9 +465,27 @@ CPU_LE( bic x0, x0, #(3 << 24) ) // Clear the EE and E0E bits for EL1
isb
ret
+2:
+#ifdef CONFIG_ARM64_VHE
+ /*
+ * Check for VHE being present. For the rest of the EL2 setup,
+ * x2 being non-zero indicates that we do have VHE, and that the
+ * kernel is intended to run at EL2.
+ */
+ mrs x2, id_aa64mmfr1_el1
+ ubfx x2, x2, #8, #4
+#else
+ mov x2, xzr
+#endif
+
/* Hyp configuration. */
-2: mov x0, #(1 << 31) // 64-bit EL1
+ mov x0, #HCR_RW // 64-bit EL1
+ cbz x2, set_hcr
+ orr x0, x0, #HCR_TGE // Enable Host Extensions
+ orr x0, x0, #HCR_E2H
+set_hcr:
msr hcr_el2, x0
+ isb
/* Generic timers. */
mrs x0, cnthctl_el2
@@ -526,6 +545,13 @@ CPU_LE( movk x0, #0x30d0, lsl #16 ) // Clear EE and E0E on LE systems
/* Stage-2 translation */
msr vttbr_el2, xzr
+ cbz x2, install_el2_stub
+
+ mov w20, #BOOT_CPU_MODE_EL2 // This CPU booted in EL2
+ isb
+ ret
+
+install_el2_stub:
/* Hypervisor stub */
adrp x0, __hyp_stub_vectors
add x0, x0, #:lo12:__hyp_stub_vectors
--
2.1.4
next prev parent reply other threads:[~2016-02-03 18:00 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-03 17:59 [PATCH v3 00/23] arm64: Virtualization Host Extension support Marc Zyngier
2016-02-03 17:59 ` [PATCH v3 01/23] arm/arm64: KVM: Add hook for C-based stage2 init Marc Zyngier
2016-02-03 17:59 ` [PATCH v3 02/23] arm64: KVM: Switch to " Marc Zyngier
2016-02-03 17:59 ` [PATCH v3 03/23] arm/arm64: Add new is_kernel_in_hyp_mode predicate Marc Zyngier
2016-02-08 14:41 ` Catalin Marinas
2016-02-03 17:59 ` [PATCH v3 04/23] arm64: Allow the arch timer to use the HYP timer Marc Zyngier
2016-02-03 17:59 ` [PATCH v3 05/23] arm64: Add ARM64_HAS_VIRT_HOST_EXTN feature Marc Zyngier
2016-02-08 14:42 ` Catalin Marinas
2016-02-03 17:59 ` [PATCH v3 06/23] arm64: KVM: Skip HYP setup when already running in HYP Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 07/23] arm64: KVM: VHE: Patch out use of HVC Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 08/23] arm64: KVM: VHE: Patch out kern_hyp_va Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 09/23] arm64: KVM: VHE: Introduce unified system register accessors Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 10/23] arm64: KVM: VHE: Differenciate host/guest sysreg save/restore Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 11/23] arm64: KVM: VHE: Split save/restore of registers shared between guest and host Marc Zyngier
2016-02-04 19:15 ` Christoffer Dall
2016-02-03 18:00 ` [PATCH v3 12/23] arm64: KVM: VHE: Use unified system register accessors Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 13/23] arm64: KVM: VHE: Enable minimal sysreg save/restore Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 14/23] arm64: KVM: VHE: Make __fpsimd_enabled VHE aware Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 15/23] arm64: KVM: VHE: Implement VHE activate/deactivate_traps Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 16/23] arm64: KVM: VHE: Use unified sysreg accessors for timer Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 17/23] arm64: KVM: VHE: Add fpsimd enabling on guest access Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 18/23] arm64: KVM: VHE: Add alternative panic handling Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 19/23] arm64: KVM: Move most of the fault decoding to C Marc Zyngier
2016-02-04 19:20 ` Christoffer Dall
2016-02-08 14:44 ` Catalin Marinas
2016-02-03 18:00 ` [PATCH v3 20/23] arm64: perf: Count EL2 events if the kernel is running in HYP Marc Zyngier
2016-02-04 19:23 ` Christoffer Dall
2016-02-05 9:02 ` Marc Zyngier
2016-02-08 14:48 ` Catalin Marinas
2016-02-03 18:00 ` [PATCH v3 21/23] arm64: hw_breakpoint: Allow EL2 breakpoints if " Marc Zyngier
2016-02-08 15:56 ` Catalin Marinas
2016-02-08 16:45 ` Marc Zyngier
2016-02-08 16:52 ` Catalin Marinas
2016-02-03 18:00 ` Marc Zyngier [this message]
2016-02-04 19:25 ` [PATCH v3 22/23] arm64: VHE: Add support for running Linux in EL2 mode Christoffer Dall
2016-02-08 15:58 ` Catalin Marinas
2016-02-03 18:00 ` [PATCH v3 23/23] arm64: Panic when VHE and non VHE CPUs coexist Marc Zyngier
2016-02-04 19:25 ` Christoffer Dall
2016-02-08 16:04 ` Catalin Marinas
2016-02-08 16:24 ` Mark Rutland
2016-02-09 12:02 ` Catalin Marinas
2016-02-04 19:26 ` [PATCH v3 00/23] arm64: Virtualization Host Extension support Christoffer Dall
2016-02-05 8:56 ` Marc Zyngier
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