We trap debug register accesses from guest all the time, and read the BCR/WCR to indicate whether the guest has enabled any break/watch points or not.
Signed-off-by: Zhichao Huang <[email protected]> --- arch/arm/include/asm/kvm_asm.h | 2 ++ arch/arm/kvm/coproc.c | 75 +++++++++++++++++++++++++++++++++++++++--- 2 files changed, 72 insertions(+), 5 deletions(-) diff --git a/arch/arm/include/asm/kvm_asm.h b/arch/arm/include/asm/kvm_asm.h index 5b1c3eb..e9e1f0a 100644 --- a/arch/arm/include/asm/kvm_asm.h +++ b/arch/arm/include/asm/kvm_asm.h @@ -65,7 +65,9 @@ #define NR_CP14_REGS 66 /* Number of regs (incl. invalid) */ #define KVM_ARM_DEBUG_HOST_INUSE_SHIFT 0 +#define KVM_ARM_DEBUG_GUEST_INUSE_SHIFT 1 #define KVM_ARM_DEBUG_HOST_INUSE (1 << KVM_ARM_DEBUG_HOST_INUSE_SHIFT) +#define KVM_ARM_DEBUG_GUEST_INUSE (1 << KVM_ARM_DEBUG_GUEST_INUSE_SHIFT) #define ARM_EXCEPTION_RESET 0 #define ARM_EXCEPTION_UNDEFINED 1 diff --git a/arch/arm/kvm/coproc.c b/arch/arm/kvm/coproc.c index b37afd6..d9dcd28b 100644 --- a/arch/arm/kvm/coproc.c +++ b/arch/arm/kvm/coproc.c @@ -220,7 +220,22 @@ bool access_vm_reg(struct kvm_vcpu *vcpu, return true; } -static bool trap_debug32(struct kvm_vcpu *vcpu, +/* Indicate whether the guest has enabled any break/watch points or not. */ +static bool guest_debug_in_use(struct kvm_vcpu *vcpu) +{ + unsigned int i; + + for (i = 0; i < ARM_MAX_BRP; i++) + if (vcpu->arch.cp14[cp14_DBGBCR0 + i] & 0x1) + return true; + for (i = 0; i < ARM_MAX_WRP; i++) + if (vcpu->arch.cp14[cp14_DBGWCR0 + i] & 0x1) + return true; + + return false; +} + +static bool __trap_debug32(struct kvm_vcpu *vcpu, const struct coproc_params *p, const struct coproc_reg *r) { @@ -232,6 +247,56 @@ static bool trap_debug32(struct kvm_vcpu *vcpu, return true; } +/* + * We want to avoid world-switching all the DBG registers all the + * time: + * + * When we are about to run a guest, we have the following cases: + * + * 1) Neither the host nor the guest has configured any [WB]points + * 2) Only the host has configured any [WB]points + * 3) Only the guest has configured any [WB]points + * 4) Both the host and the guest have configured any [WB]points + * + * - In case (1), KVM should enable trapping and swtich the register + * state on guest accesses. + * - In cases (2), (3), and (4) we must switch the register state on each + * entry/exit. + * + * For ARMv7, if the CONFIG_HAVE_HW_BREAKPOINT is set, ARM_DSCR_MDBGEN + * is always set(ARM64 use it to indicate that debug registers are actively + * in use). + * + * - We add a function reading the break/watch control variables directly to + * indicate whether the host has enabled any break/watch points or not. + * We only call the function upon guest entry, after preempt_disable() and + * local_irq_disable(), so there is no race for it. + * + * - We trap debug register accesses from guest all the time, and read the + * BCR/WCR to indicate whether the guest has enabled any break/watch points + * or not. + * + * For this, we can keep track of the host/guest use of debug registers, + * and skip the save/restore dance when neither the host nor the guest has + * configured any [WB]points. + */ +static bool trap_debug32(struct kvm_vcpu *vcpu, + const struct coproc_params *p, + const struct coproc_reg *r) +{ + __trap_debug32(vcpu, p, r); + + if (p->is_write) { + if ((vcpu->arch.cp14[r->reg] & 0x1) || + guest_debug_in_use(vcpu)) + vcpu->arch.debug_flags |= KVM_ARM_DEBUG_GUEST_INUSE; + else + vcpu->arch.debug_flags &= ~KVM_ARM_DEBUG_GUEST_INUSE; + } + + return true; +} + /* DBGIDR (RO) Debug ID */ static bool trap_dbgidr(struct kvm_vcpu *vcpu, const struct coproc_params *p, @@ -419,13 +484,13 @@ static const struct coproc_reg cp15_regs[] = { #define DBG_BCR_BVR_WCR_WVR(n) \ /* DBGBVRn */ \ { CRn( 0), CRm((n)), Op1( 0), Op2( 4), is32, \ - trap_debug32, reset_val, (cp14_DBGBVR0 + (n)), 0 }, \ + __trap_debug32, reset_val, (cp14_DBGBVR0 + (n)), 0 }, \ /* DBGBCRn */ \ { CRn( 0), CRm((n)), Op1( 0), Op2( 5), is32, \ trap_debug32, reset_val, (cp14_DBGBCR0 + (n)), 0 }, \ /* DBGWVRn */ \ { CRn( 0), CRm((n)), Op1( 0), Op2( 6), is32, \ - trap_debug32, reset_val, (cp14_DBGWVR0 + (n)), 0 }, \ + __trap_debug32, reset_val, (cp14_DBGWVR0 + (n)), 0 }, \ /* DBGWCRn */ \ { CRn( 0), CRm((n)), Op1( 0), Op2( 7), is32, \ trap_debug32, reset_val, (cp14_DBGWCR0 + (n)), 0 } @@ -462,7 +527,7 @@ static const struct coproc_reg cp14_regs[] = { /* DBGDSAR (64bit) */ { CRn( 0), CRm( 2), Op1( 0), Op2( 0), is64, trap_raz_wi }, /* DBGDSCRext */ - { CRn( 0), CRm( 2), Op1( 0), Op2( 2), is32, trap_debug32, + { CRn( 0), CRm( 2), Op1( 0), Op2( 2), is32, __trap_debug32, reset_val, cp14_DBGDSCRext, 0 }, DBG_BCR_BVR_WCR_WVR(2), /* DBGDTRTXext */ @@ -474,7 +539,7 @@ static const struct coproc_reg cp14_regs[] = { DBG_BCR_BVR_WCR_WVR(5), DBG_BCR_BVR_WCR_WVR(6), /* DBGVCR */ - { CRn( 0), CRm( 7), Op1( 0), Op2( 0), is32, trap_debug32 }, + { CRn( 0), CRm( 7), Op1( 0), Op2( 0), is32, __trap_debug32 }, DBG_BCR_BVR_WCR_WVR(7), DBG_BCR_BVR_WCR_WVR(8), DBG_BCR_BVR_WCR_WVR(9), -- 1.7.12.4 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
