Re: [PATCH v5 10/12] KVM: arm64: guest debug, HW assisted debug support
On Fri, May 29, 2015 at 10:30:26AM +0100, Alex Bennée wrote:
This adds support for userspace to control the HW debug registers for
guest debug. In the debug ioctl we copy the IMPDEF defined number of
registers into a new register set called host_debug_state. There is now
a new vcpu parameter called debug_ptr which selects which register set
is to copied into the real registers when world switch occurs.
I've moved some helper functions into the hw_breakpoint.h header for
re-use.
As with single step we need to tweak the guest registers to enable the
exceptions so we need to save and restore those bits.
Two new capabilities have been added to the KVM_EXTENSION ioctl to allow
userspace to query the number of hardware break and watch points
available on the host hardware.
Signed-off-by: Alex Bennée alex.ben...@linaro.org
---
v2
- switched to C setup
- replace host debug registers directly into context
- minor tweak to api docs
- setup right register for debug
- add FAR_EL2 to debug exit structure
- add support for trapping debug register access
v3
- remove stray trace statement
- fix spacing around operators (various)
- clean-up usage of trap_debug
- introduce debug_ptr, replace excessive memcpy stuff
- don't use memcpy in ioctl, just assign
- update cap ioctl documentation
- reword a number comments
- rename host_debug_state-external_debug_state
v4
- use the new u32/u64 split debug_ptr approach
- fix some wording/comments
v5
- don't set MDSCR_EL1.KDE (not needed)
---
Documentation/virtual/kvm/api.txt | 7 ++-
arch/arm/kvm/arm.c | 7 +++
arch/arm64/include/asm/hw_breakpoint.h | 12 +++
arch/arm64/include/asm/kvm_host.h | 3 ++-
arch/arm64/include/uapi/asm/kvm.h | 2 +-
arch/arm64/kernel/hw_breakpoint.c | 12 ---
arch/arm64/kvm/debug.c | 37
+-
arch/arm64/kvm/handle_exit.c | 6 ++
arch/arm64/kvm/reset.c | 12 +++
include/uapi/linux/kvm.h | 2 ++
10 files changed, 80 insertions(+), 20 deletions(-)
diff --git a/Documentation/virtual/kvm/api.txt
b/Documentation/virtual/kvm/api.txt
index 33c8143..ada57df 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -2668,7 +2668,7 @@ The top 16 bits of the control field are architecture
specific control
flags which can include the following:
- KVM_GUESTDBG_USE_SW_BP: using software breakpoints [x86, arm64]
- - KVM_GUESTDBG_USE_HW_BP: using hardware breakpoints [x86, s390]
+ - KVM_GUESTDBG_USE_HW_BP: using hardware breakpoints [x86, s390, arm64]
- KVM_GUESTDBG_INJECT_DB: inject DB type exception [x86]
- KVM_GUESTDBG_INJECT_BP: inject BP type exception [x86]
- KVM_GUESTDBG_EXIT_PENDING: trigger an immediate guest exit [s390]
@@ -2683,6 +2683,11 @@ updated to the correct (supplied) values.
The second part of the structure is architecture specific and
typically contains a set of debug registers.
+For arm64 the number of debug registers is implementation defined and
+can be determined by querying the KVM_CAP_GUEST_DEBUG_HW_BPS and
+KVM_CAP_GUEST_DEBUG_HW_WPS capabilities which return a positive number
+indicating the number of supported registers.
+
When debug events exit the main run loop with the reason
KVM_EXIT_DEBUG with the kvm_debug_exit_arch part of the kvm_run
structure containing architecture specific debug information.
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index 0d17c7b..6df47c1 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -307,6 +307,7 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
#define KVM_GUESTDBG_VALID_MASK (KVM_GUESTDBG_ENABLE |\
KVM_GUESTDBG_USE_SW_BP | \
+ KVM_GUESTDBG_USE_HW_BP | \
KVM_GUESTDBG_SINGLESTEP)
/**
@@ -327,6 +328,12 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu
*vcpu,
if (dbg-control KVM_GUESTDBG_ENABLE) {
vcpu-guest_debug = dbg-control;
+
+ /* Hardware assisted Break and Watch points */
+ if (vcpu-guest_debug KVM_GUESTDBG_USE_HW_BP) {
does KVM_GUESTDBG_USE_HW_BP cover watch points as well or why is this
mentionend in the comment?
I asked this once before already...
+ vcpu-arch.external_debug_state = dbg-arch;
+ }
+
} else {
/* If not enabled clear all flags */
vcpu-guest_debug = 0;
diff --git a/arch/arm64/include/asm/hw_breakpoint.h
b/arch/arm64/include/asm/hw_breakpoint.h
index 52b484b..c450552 100644
--- a/arch/arm64/include/asm/hw_breakpoint.h
+++ b/arch/arm64/include/asm/hw_breakpoint.h
@@ -130,6 +130,18 @@ static inline void ptrace_hw_copy_thread(struct
task_struct *task)
}
Re: [PATCH v5 10/12] KVM: arm64: guest debug, HW assisted debug support
Will Deacon will.dea...@arm.com writes:
Hi Alex,
On Fri, May 29, 2015 at 10:30:26AM +0100, Alex Bennée wrote:
This adds support for userspace to control the HW debug registers for
guest debug. In the debug ioctl we copy the IMPDEF defined number of
registers into a new register set called host_debug_state. There is now
a new vcpu parameter called debug_ptr which selects which register set
is to copied into the real registers when world switch occurs.
I've moved some helper functions into the hw_breakpoint.h header for
re-use.
As with single step we need to tweak the guest registers to enable the
exceptions so we need to save and restore those bits.
Two new capabilities have been added to the KVM_EXTENSION ioctl to allow
userspace to query the number of hardware break and watch points
available on the host hardware.
Signed-off-by: Alex Bennée alex.ben...@linaro.org
[...]
diff --git a/Documentation/virtual/kvm/api.txt
b/Documentation/virtual/kvm/api.txt
index 33c8143..ada57df 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -2668,7 +2668,7 @@ The top 16 bits of the control field are architecture
specific control
flags which can include the following:
- KVM_GUESTDBG_USE_SW_BP: using software breakpoints [x86, arm64]
- - KVM_GUESTDBG_USE_HW_BP: using hardware breakpoints [x86, s390]
+ - KVM_GUESTDBG_USE_HW_BP: using hardware breakpoints [x86, s390,
arm64]
- KVM_GUESTDBG_INJECT_DB: inject DB type exception [x86]
- KVM_GUESTDBG_INJECT_BP: inject BP type exception [x86]
- KVM_GUESTDBG_EXIT_PENDING: trigger an immediate guest exit [s390]
@@ -2683,6 +2683,11 @@ updated to the correct (supplied) values.
The second part of the structure is architecture specific and
typically contains a set of debug registers.
+For arm64 the number of debug registers is implementation defined and
+can be determined by querying the KVM_CAP_GUEST_DEBUG_HW_BPS and
+KVM_CAP_GUEST_DEBUG_HW_WPS capabilities which return a positive number
+indicating the number of supported registers.
+
When debug events exit the main run loop with the reason
KVM_EXIT_DEBUG with the kvm_debug_exit_arch part of the kvm_run
structure containing architecture specific debug information.
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index 0d17c7b..6df47c1 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -307,6 +307,7 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
#define KVM_GUESTDBG_VALID_MASK (KVM_GUESTDBG_ENABLE |\
KVM_GUESTDBG_USE_SW_BP | \
+KVM_GUESTDBG_USE_HW_BP | \
KVM_GUESTDBG_SINGLESTEP)
/**
@@ -327,6 +328,12 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu
*vcpu,
if (dbg-control KVM_GUESTDBG_ENABLE) {
vcpu-guest_debug = dbg-control;
+
+/* Hardware assisted Break and Watch points */
+if (vcpu-guest_debug KVM_GUESTDBG_USE_HW_BP) {
+vcpu-arch.external_debug_state = dbg-arch;
+}
+
} else {
/* If not enabled clear all flags */
vcpu-guest_debug = 0;
diff --git a/arch/arm64/include/asm/hw_breakpoint.h
b/arch/arm64/include/asm/hw_breakpoint.h
index 52b484b..c450552 100644
--- a/arch/arm64/include/asm/hw_breakpoint.h
+++ b/arch/arm64/include/asm/hw_breakpoint.h
@@ -130,6 +130,18 @@ static inline void ptrace_hw_copy_thread(struct
task_struct *task)
}
#endif
+/* Determine number of BRP registers available. */
+static inline int get_num_brps(void)
+{
+return ((read_cpuid(ID_AA64DFR0_EL1) 12) 0xf) + 1;
+}
+
+/* Determine number of WRP registers available. */
+static inline int get_num_wrps(void)
+{
+return ((read_cpuid(ID_AA64DFR0_EL1) 20) 0xf) + 1;
+}
I'm fine with moving these into the header file, but we should probably
revisit this at some point so that we use a shadow value to indicate the
minimum number of registers across the system for e.g. big.LITTLE platforms
that don't have uniform debug resources.
There is work going forward in QEMU to specify this limitation when
creating vcpus. At the moment the kernel sanity checks these are all the
same on boot up but I guess we will have to decide where the smarts will
end up. Do we:
- report the real number per real-cpu (QEMU figures out vcpu config)
or
- report the lowest common denominator
extern struct pmu perf_ops_bp;
#endif /* __KERNEL__ */
diff --git a/arch/arm64/include/asm/kvm_host.h
b/arch/arm64/include/asm/kvm_host.h
index e5040b6..498d4f7 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -113,12 +113,13 @@ struct kvm_vcpu_arch {
/*
* For debugging the guest we need to keep a set of debug
- * registers which can override the guests own debug state
+ * registers which can
Re: [PATCH v5 10/12] KVM: arm64: guest debug, HW assisted debug support
Hi Alex,
On Fri, May 29, 2015 at 10:30:26AM +0100, Alex Bennée wrote:
This adds support for userspace to control the HW debug registers for
guest debug. In the debug ioctl we copy the IMPDEF defined number of
registers into a new register set called host_debug_state. There is now
a new vcpu parameter called debug_ptr which selects which register set
is to copied into the real registers when world switch occurs.
I've moved some helper functions into the hw_breakpoint.h header for
re-use.
As with single step we need to tweak the guest registers to enable the
exceptions so we need to save and restore those bits.
Two new capabilities have been added to the KVM_EXTENSION ioctl to allow
userspace to query the number of hardware break and watch points
available on the host hardware.
Signed-off-by: Alex Bennée alex.ben...@linaro.org
[...]
diff --git a/Documentation/virtual/kvm/api.txt
b/Documentation/virtual/kvm/api.txt
index 33c8143..ada57df 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -2668,7 +2668,7 @@ The top 16 bits of the control field are architecture
specific control
flags which can include the following:
- KVM_GUESTDBG_USE_SW_BP: using software breakpoints [x86, arm64]
- - KVM_GUESTDBG_USE_HW_BP: using hardware breakpoints [x86, s390]
+ - KVM_GUESTDBG_USE_HW_BP: using hardware breakpoints [x86, s390, arm64]
- KVM_GUESTDBG_INJECT_DB: inject DB type exception [x86]
- KVM_GUESTDBG_INJECT_BP: inject BP type exception [x86]
- KVM_GUESTDBG_EXIT_PENDING: trigger an immediate guest exit [s390]
@@ -2683,6 +2683,11 @@ updated to the correct (supplied) values.
The second part of the structure is architecture specific and
typically contains a set of debug registers.
+For arm64 the number of debug registers is implementation defined and
+can be determined by querying the KVM_CAP_GUEST_DEBUG_HW_BPS and
+KVM_CAP_GUEST_DEBUG_HW_WPS capabilities which return a positive number
+indicating the number of supported registers.
+
When debug events exit the main run loop with the reason
KVM_EXIT_DEBUG with the kvm_debug_exit_arch part of the kvm_run
structure containing architecture specific debug information.
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index 0d17c7b..6df47c1 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -307,6 +307,7 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
#define KVM_GUESTDBG_VALID_MASK (KVM_GUESTDBG_ENABLE |\
KVM_GUESTDBG_USE_SW_BP | \
+ KVM_GUESTDBG_USE_HW_BP | \
KVM_GUESTDBG_SINGLESTEP)
/**
@@ -327,6 +328,12 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu
*vcpu,
if (dbg-control KVM_GUESTDBG_ENABLE) {
vcpu-guest_debug = dbg-control;
+
+ /* Hardware assisted Break and Watch points */
+ if (vcpu-guest_debug KVM_GUESTDBG_USE_HW_BP) {
+ vcpu-arch.external_debug_state = dbg-arch;
+ }
+
} else {
/* If not enabled clear all flags */
vcpu-guest_debug = 0;
diff --git a/arch/arm64/include/asm/hw_breakpoint.h
b/arch/arm64/include/asm/hw_breakpoint.h
index 52b484b..c450552 100644
--- a/arch/arm64/include/asm/hw_breakpoint.h
+++ b/arch/arm64/include/asm/hw_breakpoint.h
@@ -130,6 +130,18 @@ static inline void ptrace_hw_copy_thread(struct
task_struct *task)
}
#endif
+/* Determine number of BRP registers available. */
+static inline int get_num_brps(void)
+{
+ return ((read_cpuid(ID_AA64DFR0_EL1) 12) 0xf) + 1;
+}
+
+/* Determine number of WRP registers available. */
+static inline int get_num_wrps(void)
+{
+ return ((read_cpuid(ID_AA64DFR0_EL1) 20) 0xf) + 1;
+}
I'm fine with moving these into the header file, but we should probably
revisit this at some point so that we use a shadow value to indicate the
minimum number of registers across the system for e.g. big.LITTLE platforms
that don't have uniform debug resources.
extern struct pmu perf_ops_bp;
#endif /* __KERNEL__ */
diff --git a/arch/arm64/include/asm/kvm_host.h
b/arch/arm64/include/asm/kvm_host.h
index e5040b6..498d4f7 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -113,12 +113,13 @@ struct kvm_vcpu_arch {
/*
* For debugging the guest we need to keep a set of debug
- * registers which can override the guests own debug state
+ * registers which can override the guest's own debug state
* while being used. These are set via the KVM_SET_GUEST_DEBUG
* ioctl.
*/
struct kvm_guest_debug_arch *debug_ptr;
struct kvm_guest_debug_arch vcpu_debug_state;
+ struct kvm_guest_debug_arch external_debug_state;
/* Pointer to host CPU context */
kvm_cpu_context_t *host_cpu_context;
diff
[PATCH v5 10/12] KVM: arm64: guest debug, HW assisted debug support
This adds support for userspace to control the HW debug registers for
guest debug. In the debug ioctl we copy the IMPDEF defined number of
registers into a new register set called host_debug_state. There is now
a new vcpu parameter called debug_ptr which selects which register set
is to copied into the real registers when world switch occurs.
I've moved some helper functions into the hw_breakpoint.h header for
re-use.
As with single step we need to tweak the guest registers to enable the
exceptions so we need to save and restore those bits.
Two new capabilities have been added to the KVM_EXTENSION ioctl to allow
userspace to query the number of hardware break and watch points
available on the host hardware.
Signed-off-by: Alex Bennée alex.ben...@linaro.org
---
v2
- switched to C setup
- replace host debug registers directly into context
- minor tweak to api docs
- setup right register for debug
- add FAR_EL2 to debug exit structure
- add support for trapping debug register access
v3
- remove stray trace statement
- fix spacing around operators (various)
- clean-up usage of trap_debug
- introduce debug_ptr, replace excessive memcpy stuff
- don't use memcpy in ioctl, just assign
- update cap ioctl documentation
- reword a number comments
- rename host_debug_state-external_debug_state
v4
- use the new u32/u64 split debug_ptr approach
- fix some wording/comments
v5
- don't set MDSCR_EL1.KDE (not needed)
---
Documentation/virtual/kvm/api.txt | 7 ++-
arch/arm/kvm/arm.c | 7 +++
arch/arm64/include/asm/hw_breakpoint.h | 12 +++
arch/arm64/include/asm/kvm_host.h | 3 ++-
arch/arm64/include/uapi/asm/kvm.h | 2 +-
arch/arm64/kernel/hw_breakpoint.c | 12 ---
arch/arm64/kvm/debug.c | 37 +-
arch/arm64/kvm/handle_exit.c | 6 ++
arch/arm64/kvm/reset.c | 12 +++
include/uapi/linux/kvm.h | 2 ++
10 files changed, 80 insertions(+), 20 deletions(-)
diff --git a/Documentation/virtual/kvm/api.txt
b/Documentation/virtual/kvm/api.txt
index 33c8143..ada57df 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -2668,7 +2668,7 @@ The top 16 bits of the control field are architecture
specific control
flags which can include the following:
- KVM_GUESTDBG_USE_SW_BP: using software breakpoints [x86, arm64]
- - KVM_GUESTDBG_USE_HW_BP: using hardware breakpoints [x86, s390]
+ - KVM_GUESTDBG_USE_HW_BP: using hardware breakpoints [x86, s390, arm64]
- KVM_GUESTDBG_INJECT_DB: inject DB type exception [x86]
- KVM_GUESTDBG_INJECT_BP: inject BP type exception [x86]
- KVM_GUESTDBG_EXIT_PENDING: trigger an immediate guest exit [s390]
@@ -2683,6 +2683,11 @@ updated to the correct (supplied) values.
The second part of the structure is architecture specific and
typically contains a set of debug registers.
+For arm64 the number of debug registers is implementation defined and
+can be determined by querying the KVM_CAP_GUEST_DEBUG_HW_BPS and
+KVM_CAP_GUEST_DEBUG_HW_WPS capabilities which return a positive number
+indicating the number of supported registers.
+
When debug events exit the main run loop with the reason
KVM_EXIT_DEBUG with the kvm_debug_exit_arch part of the kvm_run
structure containing architecture specific debug information.
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index 0d17c7b..6df47c1 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -307,6 +307,7 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
#define KVM_GUESTDBG_VALID_MASK (KVM_GUESTDBG_ENABLE |\
KVM_GUESTDBG_USE_SW_BP | \
+ KVM_GUESTDBG_USE_HW_BP | \
KVM_GUESTDBG_SINGLESTEP)
/**
@@ -327,6 +328,12 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu
*vcpu,
if (dbg-control KVM_GUESTDBG_ENABLE) {
vcpu-guest_debug = dbg-control;
+
+ /* Hardware assisted Break and Watch points */
+ if (vcpu-guest_debug KVM_GUESTDBG_USE_HW_BP) {
+ vcpu-arch.external_debug_state = dbg-arch;
+ }
+
} else {
/* If not enabled clear all flags */
vcpu-guest_debug = 0;
diff --git a/arch/arm64/include/asm/hw_breakpoint.h
b/arch/arm64/include/asm/hw_breakpoint.h
index 52b484b..c450552 100644
--- a/arch/arm64/include/asm/hw_breakpoint.h
+++ b/arch/arm64/include/asm/hw_breakpoint.h
@@ -130,6 +130,18 @@ static inline void ptrace_hw_copy_thread(struct
task_struct *task)
}
#endif
+/* Determine number of BRP registers available. */
+static inline int get_num_brps(void)
+{
+ return ((read_cpuid(ID_AA64DFR0_EL1) 12) 0xf) + 1;
+}
+
+/* Determine number of WRP registers available. */
+static inline int get_num_wrps(void)
+{
+ return
