Avoid world-switching all the debug registers when neither the host nor the guest has configured any [WB]points. Signed-off-by: Zhichao Huang <zhichao.huang@xxxxxxxxxx> --- 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 -- 1.7.12.4 _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
