[PATCH v4 14/15] KVM: arm: implement lazy world switch for debug registers
From: Zhichao Huang <hidden>
Date: 2015-08-10 13:26:06
Also in:
kvm, kvmarm
Subsystem:
arm port, the rest · Maintainers:
Russell King, Linus Torvalds
Avoid world-switching all the debug registers when neither the host nor the guest has configured any [WB]points. Signed-off-by: Zhichao Huang <redacted> --- arch/arm/kvm/interrupts_head.S | 23 +++++++++++++++++++++-- 1 file changed, 21 insertions(+), 2 deletions(-)
diff --git a/arch/arm/kvm/interrupts_head.S b/arch/arm/kvm/interrupts_head.S
index b9e7410..7ad0adf 100644
--- a/arch/arm/kvm/interrupts_head.S
+++ b/arch/arm/kvm/interrupts_head.S@@ -332,6 +332,21 @@ vcpu .req r0 @ vcpu pointer always in r0 sub r12, r2, r12 @ How many WPs to skip .endm +/* If VCPU_DEBUG_FLAGS is not set, it means that neither the host + * nor the guest has configured any [WB]points. + * + * We avoid world-switching all the debug registers in that case. + * + * Assume vcpu pointer in vcpu reg + * + * clobbers r2 + */ +.macro skip_debug_state target + ldr r2, [vcpu, #VCPU_DEBUG_FLAGS] + cmp r2, #0 + beq \target +.endm + /* Reads cp14 registers from hardware. * Writes cp14 registers in-order to the CP14 struct pointed to by r10 *
@@ -340,12 +355,14 @@ vcpu .req r0 @ vcpu pointer always in r0 * Clobbers r2-r12 */ .macro save_debug_state + skip_debug_state 9999f + read_hw_dbg_num cp14_read_and_str r10, 4, cp14_DBGBVR0, r11 cp14_read_and_str r10, 5, cp14_DBGBCR0, r11 cp14_read_and_str r10, 6, cp14_DBGWVR0, r12 cp14_read_and_str r10, 7, cp14_DBGWCR0, r12 - +9999: /* DBGDSCR reg */ mrc p14, 0, r2, c0, c1, 0 str r2, [r10, #CP14_OFFSET(cp14_DBGDSCRext)]
@@ -359,12 +376,14 @@ vcpu .req r0 @ vcpu pointer always in r0 * Clobbers r2-r12 */ .macro restore_debug_state + skip_debug_state 9999f + read_hw_dbg_num cp14_ldr_and_write r10, 4, cp14_DBGBVR0, r11 cp14_ldr_and_write r10, 5, cp14_DBGBCR0, r11 cp14_ldr_and_write r10, 6, cp14_DBGWVR0, r12 cp14_ldr_and_write r10, 7, cp14_DBGWCR0, r12 - +9999: /* DBGDSCR reg */ ldr r2, [r10, #CP14_OFFSET(cp14_DBGDSCRext)] mcr p14, 0, r2, c0, c2, 2
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1.7.12.4