From: zhichao.huang@linaro.org (Zhichao Huang)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v4 13/15] KVM: arm: keep track of guest use of the debug registers
Date: Mon, 10 Aug 2015 21:26:05 +0800 [thread overview]
Message-ID: <1439213167-8988-14-git-send-email-zhichao.huang@linaro.org> (raw)
In-Reply-To: <1439213167-8988-1-git-send-email-zhichao.huang@linaro.org>
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 <zhichao.huang@linaro.org>
---
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
next prev parent reply other threads:[~2015-08-10 13:26 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-10 13:25 [PATCH v4 00/15] KVM: arm: debug infrastructure support Zhichao Huang
2015-08-10 13:25 ` [PATCH v4 01/15] KVM: arm: plug guest debug exploit Zhichao Huang
2015-09-02 11:38 ` Christoffer Dall
2015-09-29 5:13 ` Zhichao Huang
2015-08-10 13:25 ` [PATCH v4 02/15] KVM: arm: rename pm_fake handler to trap_raz_wi Zhichao Huang
2015-08-10 13:25 ` [PATCH v4 03/15] KVM: arm: enable to use the ARM_DSCR_MDBGEN macro from KVM assembly code Zhichao Huang
2015-08-10 13:25 ` [PATCH v4 04/15] KVM: arm: common infrastructure for handling AArch32 CP14/CP15 Zhichao Huang
2015-09-02 13:09 ` Christoffer Dall
2015-08-10 13:25 ` [PATCH v4 05/15] KVM: arm: check ordering of all system register tables Zhichao Huang
2015-08-10 13:25 ` [PATCH v4 06/15] KVM: arm: add trap handlers for 32-bit debug registers Zhichao Huang
2015-09-02 16:03 ` Christoffer Dall
2015-08-10 13:25 ` [PATCH v4 07/15] KVM: arm: add trap handlers for 64-bit " Zhichao Huang
2015-08-10 13:26 ` [PATCH v4 08/15] KVM: arm: add a trace event for cp14 traps Zhichao Huang
2015-08-10 13:26 ` [PATCH v4 09/15] KVM: arm: redefine kvm_cpu_context_t to save the host cp14 states Zhichao Huang
2015-09-02 14:54 ` Christoffer Dall
2015-08-10 13:26 ` [PATCH v4 10/15] KVM: arm: implement world switch for debug registers Zhichao Huang
2015-09-02 14:53 ` Christoffer Dall
2015-09-29 5:32 ` Zhichao Huang
2015-09-29 7:34 ` Christoffer Dall
2015-08-10 13:26 ` [PATCH v4 11/15] KVM: arm: add a function to keep track of host use of the " Zhichao Huang
2015-09-02 15:40 ` Christoffer Dall
2015-08-10 13:26 ` [PATCH v4 12/15] KVM: arm: " Zhichao Huang
2015-09-02 15:44 ` Christoffer Dall
2015-08-10 13:26 ` Zhichao Huang [this message]
2015-09-02 16:01 ` [PATCH v4 13/15] KVM: arm: keep track of guest " Christoffer Dall
2015-09-29 5:36 ` Zhichao Huang
2015-08-10 13:26 ` [PATCH v4 14/15] KVM: arm: implement lazy world switch for " Zhichao Huang
2015-09-02 16:06 ` Christoffer Dall
2015-08-10 13:26 ` [PATCH v4 15/15] KVM: arm: enable trapping of all " Zhichao Huang
2015-09-02 16:08 ` Christoffer Dall
2015-09-29 5:41 ` Zhichao Huang
2015-09-29 7:38 ` Christoffer Dall
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1439213167-8988-14-git-send-email-zhichao.huang@linaro.org \
--to=zhichao.huang@linaro.org \
--cc=linux-arm-kernel@lists.infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).