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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [XEN v8 2/2] xen/arm64: io: Support instructions (for which ISS is not valid) on emulated MMIO region using MMIO/ioreq handler
When an instruction is trapped in Xen due to translation fault, Xen
checks if the ISS is valid. If not, Xen tries to resolve the translation
fault using p2m page tables. In case if it is a data abort, Xen will
try to map the mmio region to the guest (ie tries to emulate the mmio
region).
If the ISS is not valid and it is a data abort, then Xen tries to
decode the instruction. In case of ioreq, Xen saves the decoding state,
rn and imm9 to vcpu_io. Whenever the vcpu handles the ioreq successfully,
it will read the decoding state to determine if the instruction decoded
was a ldr/str post indexing (ie INSTR_LDR_STR_POSTINDEXING). If so, it
uses these details to post increment rn.
In case of mmio handler, if the mmio operation was successful, then Xen
retrives the decoding state, rn and imm9. For state ==
INSTR_LDR_STR_POSTINDEXING, Xen will update rn.
If there is an error encountered while decoding the instruction, Xen
will issue an abort to the guest. If the instruction was trapped due
to stage1 page translation table walk, Xen will update the page tables
(under the assumption that they are in non-MMIO region) and will return
to the guest so that it can retry the instruction. To handle all these
different states, we have introduced 'enum instr_decode_state'.
Signed-off-by: Ayan Kumar Halder <ayankuma@xxxxxxxxxx>
---
Changelog :-
v2..v5 - Mentioned in the cover letter.
v6 - 1. Mantained the decoding state of the instruction. This is used by the
caller to either abort the guest or retry or ignore or perform read/write on
the mmio region.
2. try_decode() invokes decoding for both aarch64 and thumb state. (Previously
it used to invoke decoding only for aarch64 state). Thus, it handles all the
checking of the registers before invoking any decoding of instruction.
try_decode_instruction_invalid_iss() has thus been removed.
3. Introduced a new field('enum instr_decode_state state') inside
'struct instr_details'. This holds the decoding state of the instruction.
This is later read by the post_increment_register() to determine if rn needs to
be incremented. Also, this is read by the callers of try_decode_instruction()
to determine if the instruction was valid or ignored or to be retried or
error or decoded successfully.
4. Also stored 'instr_details' inside 'struct ioreq'. This enables
arch_ioreq_complete_mmio() to invoke post_increment_register() without decoding
the instruction again.
5. Check hsr.dabt.valid in do_trap_stage2_abort_guest(). If it is not valid,
then decode the instruction. This ensures that try_handle_mmio() is invoked only
when the instruction is either valid or decoded successfully.
6. Inside do_trap_stage2_abort_guest(), if hsr.dabt.valid is not set, then
resolve the translation fault before trying to decode the instruction. If
translation fault is resolved, then return to the guest to execute the
instruction
again.
v7 - 1. Moved the decoding instruction details ie instr_details from 'struct
ioreq'
to 'struct vcpu_io'.
2. The instruction is decoded only when we get a data abort.
3. Replaced ASSERT_UNREACHABLE() with domain_crash(). The reason being asserts
can be disabled in some builds. In this scenario when the guest's cpsr is in an
erroneous state, Xen should crash the guest.
4. Introduced check_p2m() which invokes p2m_resolve_translation_fault() and
try_map_mmio() to resolve translation fault by configuring the page tables. This
gets invoked first if ISS is invalid and it is an instruction abort. If it is
a data abort and hsr.dabt.s1ptw is set or try_handle_mmio() returns
IO_UNHANDLED,
then check_p2m() gets invoked again.
v8 - 1. Removed the handling of data abort when info->dabt.cache is set. This
will
be implemented in a subsequent patch. (Not as part of this series)
2. When the data abort is due to access to stage 1 translation tables, Xen will
try to fix the mapping of the page table for the corresponding address. If this
returns an error, Xen will abort the guest. Else, it will ask the guest to retry
the instruction.
3. Changed v->io.info.dabt_instr from pointer to variable. The reason being that
arch_ioreq_complete_mmio() is called from leave_hypervisor_to_guest().
That is after do_trap_stage2_abort_guest() has been invoked. So the original
variable will be no longer valid.
4. Some other style issues pointed out in v7.
xen/arch/arm/arm32/traps.c | 7 +++
xen/arch/arm/arm64/traps.c | 47 +++++++++++++++
xen/arch/arm/decode.c | 1 +
xen/arch/arm/include/asm/domain.h | 4 ++
xen/arch/arm/include/asm/mmio.h | 15 ++++-
xen/arch/arm/include/asm/traps.h | 2 +
xen/arch/arm/io.c | 98 ++++++++++++++++++++-----------
xen/arch/arm/ioreq.c | 7 ++-
xen/arch/arm/traps.c | 80 +++++++++++++++++++++----
xen/arch/x86/include/asm/ioreq.h | 3 +
xen/include/xen/sched.h | 2 +
11 files changed, 217 insertions(+), 49 deletions(-)
diff --git a/xen/arch/arm/arm32/traps.c b/xen/arch/arm/arm32/traps.c
index 9c9790a6d1..70c6238196 100644
--- a/xen/arch/arm/arm32/traps.c
+++ b/xen/arch/arm/arm32/traps.c
@@ -18,9 +18,11 @@
#include <xen/lib.h>
#include <xen/kernel.h>
+#include <xen/sched.h>
#include <public/xen.h>
+#include <asm/mmio.h>
#include <asm/processor.h>
#include <asm/traps.h>
@@ -82,6 +84,11 @@ void do_trap_data_abort(struct cpu_user_regs *regs)
do_unexpected_trap("Data Abort", regs);
}
+void post_increment_register(const struct instr_details *instr)
+{
+ domain_crash(current->domain);
+}
+
/*
* Local variables:
* mode: C
diff --git a/xen/arch/arm/arm64/traps.c b/xen/arch/arm/arm64/traps.c
index 9113a15c7a..a6766689b3 100644
--- a/xen/arch/arm/arm64/traps.c
+++ b/xen/arch/arm/arm64/traps.c
@@ -23,6 +23,7 @@
#include <asm/processor.h>
#include <public/xen.h>
+#include <xen/sched.h>
static const char *handler[]= {
"Synchronous Abort",
@@ -44,6 +45,52 @@ void do_bad_mode(struct cpu_user_regs *regs, int reason)
panic("bad mode\n");
}
+void post_increment_register(const struct instr_details *instr)
+{
+ struct cpu_user_regs *regs = guest_cpu_user_regs();
+ register_t val = 0;
+
+ /* Currently, we handle only ldr/str post indexing instructions */
+ if ( instr->state != INSTR_LDR_STR_POSTINDEXING )
+ return;
+
+ /*
+ * Handle when rn = SP
+ * Refer ArmV8 ARM DDI 0487G.b, Page - D1-2463 "Stack pointer register
+ * selection"
+ * t = SP_EL0
+ * h = SP_ELx
+ * and M[3:0] (Page - C5-474 "When exception taken from AArch64 state:")
+ */
+ if (instr->rn == 31 )
+ {
+ if ( (regs->cpsr & PSR_MODE_MASK) == PSR_MODE_EL1h )
+ val = regs->sp_el1;
+ else if ( ((regs->cpsr & PSR_MODE_MASK) == PSR_MODE_EL1t) ||
+ ((regs->cpsr & PSR_MODE_MASK) == PSR_MODE_EL0t) )
+ val = regs->sp_el0;
+ else
+ {
+ domain_crash(current->domain);
+ return;
+ }
+ }
+ else
+ val = get_user_reg(regs, instr->rn);
+
+ val += instr->imm9;
+
+ if ( instr->rn == 31 )
+ {
+ if ( (regs->cpsr & PSR_MODE_MASK) == PSR_MODE_EL1h )
+ regs->sp_el1 = val;
+ else
+ regs->sp_el0 = val;
+ }
+ else
+ set_user_reg(regs, instr->rn, val);
+}
+
/*
* Local variables:
* mode: C
diff --git a/xen/arch/arm/decode.c b/xen/arch/arm/decode.c
index 3c3cd703e0..e90f95ecd3 100644
--- a/xen/arch/arm/decode.c
+++ b/xen/arch/arm/decode.c
@@ -146,6 +146,7 @@ static int decode_arm64(register_t pc, mmio_info_t *info)
update_dabt(dabt, opcode.ldr_str.rt, opcode.ldr_str.size, false);
+ dabt_instr->state = INSTR_LDR_STR_POSTINDEXING;
dabt_instr->rn = opcode.ldr_str.rn;
dabt_instr->imm9 = opcode.ldr_str.imm9;
diff --git a/xen/arch/arm/include/asm/domain.h
b/xen/arch/arm/include/asm/domain.h
index 9b3647587a..40b9125141 100644
--- a/xen/arch/arm/include/asm/domain.h
+++ b/xen/arch/arm/include/asm/domain.h
@@ -266,6 +266,10 @@ static inline void arch_vcpu_block(struct vcpu *v) {}
/* vPCI is not available on Arm */
#define has_vpci(d) ({ (void)(d); false; })
+struct arch_vcpu_io {
+ struct instr_details dabt_instr; /* when the instruction is decoded */
+};
+
#endif /* __ASM_DOMAIN_H__ */
/*
diff --git a/xen/arch/arm/include/asm/mmio.h b/xen/arch/arm/include/asm/mmio.h
index 3354d9c635..745130b7fe 100644
--- a/xen/arch/arm/include/asm/mmio.h
+++ b/xen/arch/arm/include/asm/mmio.h
@@ -26,12 +26,22 @@
#define MAX_IO_HANDLER 16
+enum instr_decode_state
+{
+ INSTR_ERROR, /* Error encountered while decoding instr
*/
+ INSTR_VALID, /* ISS is valid, so no need to decode */
+ INSTR_LDR_STR_POSTINDEXING, /* Instruction is decoded successfully.
+ It is ldr/str post indexing */
+ INSTR_RETRY /* Instruction is to be retried */
+};
+
typedef struct
{
struct hsr_dabt dabt;
struct instr_details {
unsigned long rn:5;
signed int imm9:9;
+ enum instr_decode_state state;
} dabt_instr;
paddr_t gpa;
} mmio_info_t;
@@ -69,14 +79,15 @@ struct vmmio {
};
enum io_state try_handle_mmio(struct cpu_user_regs *regs,
- const union hsr hsr,
- paddr_t gpa);
+ mmio_info_t *info);
void register_mmio_handler(struct domain *d,
const struct mmio_handler_ops *ops,
paddr_t addr, paddr_t size, void *priv);
int domain_io_init(struct domain *d, int max_count);
void domain_io_free(struct domain *d);
+void try_decode_instruction(const struct cpu_user_regs *regs,
+ mmio_info_t *info);
#endif /* __ASM_ARM_MMIO_H__ */
diff --git a/xen/arch/arm/include/asm/traps.h b/xen/arch/arm/include/asm/traps.h
index 2ed2b85c6f..95c46ad391 100644
--- a/xen/arch/arm/include/asm/traps.h
+++ b/xen/arch/arm/include/asm/traps.h
@@ -109,6 +109,8 @@ static inline register_t sign_extend(const struct hsr_dabt
dabt, register_t r)
return r;
}
+void post_increment_register(const struct instr_details *instr);
+
#endif /* __ASM_ARM_TRAPS__ */
/*
* Local variables:
diff --git a/xen/arch/arm/io.c b/xen/arch/arm/io.c
index a289d393f9..203466b869 100644
--- a/xen/arch/arm/io.c
+++ b/xen/arch/arm/io.c
@@ -95,57 +95,87 @@ static const struct mmio_handler *find_mmio_handler(struct
domain *d,
return handler;
}
+void try_decode_instruction(const struct cpu_user_regs *regs,
+ mmio_info_t *info)
+{
+ int rc;
+
+ /*
+ * Erratum 766422: Thumb store translation fault to Hypervisor may
+ * not have correct HSR Rt value.
+ */
+ if ( check_workaround_766422() && (regs->cpsr & PSR_THUMB) &&
+ info->dabt.write )
+ {
+ rc = decode_instruction(regs, info);
+ if ( rc )
+ {
+ gprintk(XENLOG_DEBUG, "Unable to decode instruction\n");
+ info->dabt_instr.state = INSTR_ERROR;
+ return;
+ }
+ }
+
+ /* If ISS is valid, then no need to decode the instruction any further */
+ if ( info->dabt.valid )
+ {
+ info->dabt_instr.state = INSTR_VALID;
+ return;
+ }
+
+ /*
+ * Xen should not decode the instruction when it was trapped due to
+ * translation fault.
+ */
+ if ( info->dabt.s1ptw )
+ {
+ info->dabt_instr.state = INSTR_RETRY;
+ return;
+ }
+
+ /*
+ * Armv8 processor does not provide a valid syndrome for decoding some
+ * instructions. So in order to process these instructions, Xen must
+ * decode them.
+ */
+ rc = decode_instruction(regs, info);
+ if ( rc )
+ {
+ gprintk(XENLOG_ERR, "Unable to decode instruction\n");
+ info->dabt_instr.state = INSTR_ERROR;
+ }
+}
+
enum io_state try_handle_mmio(struct cpu_user_regs *regs,
- const union hsr hsr,
- paddr_t gpa)
+ mmio_info_t *info)
{
struct vcpu *v = current;
const struct mmio_handler *handler = NULL;
- const struct hsr_dabt dabt = hsr.dabt;
- mmio_info_t info = {
- .gpa = gpa,
- .dabt = dabt
- };
+ int rc;
- ASSERT(hsr.ec == HSR_EC_DATA_ABORT_LOWER_EL);
+ ASSERT(info->dabt.ec == HSR_EC_DATA_ABORT_LOWER_EL);
- handler = find_mmio_handler(v->domain, info.gpa);
+ handler = find_mmio_handler(v->domain, info->gpa);
if ( !handler )
{
- int rc;
-
- rc = try_fwd_ioserv(regs, v, &info);
+ rc = try_fwd_ioserv(regs, v, info);
if ( rc == IO_HANDLED )
return handle_ioserv(regs, v);
return rc;
}
- /* All the instructions used on emulated MMIO region should be valid */
- if ( !dabt.valid )
- return IO_ABORT;
-
/*
- * Erratum 766422: Thumb store translation fault to Hypervisor may
- * not have correct HSR Rt value.
+ * At this point, we know that the instruction is either valid or has been
+ * decoded successfully. Thus, Xen should be allowed to execute the
+ * instruction on the emulated MMIO region.
*/
- if ( check_workaround_766422() && (regs->cpsr & PSR_THUMB) &&
- dabt.write )
- {
- int rc;
-
- rc = decode_instruction(regs, &info);
- if ( rc )
- {
- gprintk(XENLOG_DEBUG, "Unable to decode instruction\n");
- return IO_ABORT;
- }
- }
-
- if ( info.dabt.write )
- return handle_write(handler, v, &info);
+ if ( info->dabt.write )
+ rc = handle_write(handler, v, info);
else
- return handle_read(handler, v, &info);
+ rc = handle_read(handler, v, info);
+
+ return rc;
}
void register_mmio_handler(struct domain *d,
diff --git a/xen/arch/arm/ioreq.c b/xen/arch/arm/ioreq.c
index 308650b400..3c0a935ccf 100644
--- a/xen/arch/arm/ioreq.c
+++ b/xen/arch/arm/ioreq.c
@@ -47,6 +47,7 @@ enum io_state try_fwd_ioserv(struct cpu_user_regs *regs,
struct vcpu *v, mmio_info_t *info)
{
struct vcpu_io *vio = &v->io;
+ struct dabt_instr instr = info->dabt_instr;
ioreq_t p = {
.type = IOREQ_TYPE_COPY,
.addr = info->gpa,
@@ -76,10 +77,8 @@ enum io_state try_fwd_ioserv(struct cpu_user_regs *regs,
if ( !s )
return IO_UNHANDLED;
- if ( !info->dabt.valid )
- return IO_ABORT;
-
vio->req = p;
+ vio->info.dabt_instr = instr;
rc = ioreq_send(s, &p, 0);
if ( rc != IO_RETRY || v->domain->is_shutting_down )
@@ -95,6 +94,7 @@ enum io_state try_fwd_ioserv(struct cpu_user_regs *regs,
bool arch_ioreq_complete_mmio(void)
{
struct vcpu *v = current;
+ struct instr_details dabt_instr = v->io.info.dabt_instr;
struct cpu_user_regs *regs = guest_cpu_user_regs();
const union hsr hsr = { .bits = regs->hsr };
@@ -106,6 +106,7 @@ bool arch_ioreq_complete_mmio(void)
if ( handle_ioserv(regs, v) == IO_HANDLED )
{
+ post_increment_register(&dabt_instr);
advance_pc(regs, hsr);
return true;
}
diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 9339d12f58..455e51cdbe 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -1893,6 +1893,21 @@ static bool try_map_mmio(gfn_t gfn)
return !map_regions_p2mt(d, gfn, 1, mfn, p2m_mmio_direct_c);
}
+static inline bool check_p2m(bool is_data, paddr_t gpa)
+{
+ /*
+ * First check if the translation fault can be resolved by the P2M
subsystem.
+ * If that's the case nothing else to do.
+ */
+ if ( p2m_resolve_translation_fault(current->domain,gaddr_to_gfn(gpa)) )
+ return true;
+
+ if ( is_data && try_map_mmio(gaddr_to_gfn(gpa)) )
+ return true;
+
+ return false;
+}
+
static void do_trap_stage2_abort_guest(struct cpu_user_regs *regs,
const union hsr hsr)
{
@@ -1906,6 +1921,7 @@ static void do_trap_stage2_abort_guest(struct
cpu_user_regs *regs,
paddr_t gpa;
uint8_t fsc = xabt.fsc & ~FSC_LL_MASK;
bool is_data = (hsr.ec == HSR_EC_DATA_ABORT_LOWER_EL);
+ mmio_info_t info;
/*
* If this bit has been set, it means that this stage-2 abort is caused
@@ -1959,6 +1975,25 @@ static void do_trap_stage2_abort_guest(struct
cpu_user_regs *regs,
return;
}
case FSC_FLT_TRANS:
+ {
+ info.gpa = gpa;
+ info.dabt = hsr.dabt;
+
+ /* Check that the ISS is invalid and it is not data abort. */
+ if ( !hsr.dabt.valid && !is_data )
+ {
+
+ /*
+ * Assumption :- Most of the times when we get a translation fault
+ * and the ISS is invalid, the underlying cause is that the page
+ * tables have not been set up correctly.
+ */
+ if ( check_p2m(is_data, gpa) )
+ return;
+ else
+ goto inject_abt;
+ }
+
/*
* Attempt first to emulate the MMIO as the data abort will
* likely happen in an emulated region.
@@ -1967,13 +2002,45 @@ static void do_trap_stage2_abort_guest(struct
cpu_user_regs *regs,
*/
if ( is_data )
{
- enum io_state state = try_handle_mmio(regs, hsr, gpa);
+ enum io_state state;
+
+ try_decode_instruction(regs, &info);
+
+ /*
+ * If Xen could not decode the instruction for any reason, then it
+ * should ask the caller to abort the guest.
+ */
+ if ( info.dabt_instr.state == INSTR_ERROR )
+ goto inject_abt;
+
+ /*
+ * When the instruction needs to be retried by the guest after
+ * resolving the translation fault.
+ */
+ else if ( info.dabt_instr.state == INSTR_RETRY )
+ {
+ /*
+ * Try resolving the translation fault for access to the stage1
+ * translation tables which should be in non MMIO region.
+ */
+ if ( !check_p2m(false, gpa) )
+ goto inject_abt;
+ }
+
+ state = try_handle_mmio(regs, &info);
switch ( state )
{
case IO_ABORT:
goto inject_abt;
case IO_HANDLED:
+ /*
+ * If the instruction was decoded and has executed successfully
+ * on the MMIO region, then Xen should execute the next part of
+ * the instruction. (for eg increment the rn if it is a
+ * post-indexing instruction.
+ */
+ post_increment_register(&info.dabt_instr);
advance_pc(regs, hsr);
return;
case IO_RETRY:
@@ -1985,18 +2052,11 @@ static void do_trap_stage2_abort_guest(struct
cpu_user_regs *regs,
}
}
- /*
- * First check if the translation fault can be resolved by the
- * P2M subsystem. If that's the case nothing else to do.
- */
- if ( p2m_resolve_translation_fault(current->domain,
- gaddr_to_gfn(gpa)) )
- return;
-
- if ( is_data && try_map_mmio(gaddr_to_gfn(gpa)) )
+ if ( check_p2m(is_data, gpa) )
return;
break;
+ }
default:
gprintk(XENLOG_WARNING,
"Unsupported FSC: HSR=%#"PRIregister" DFSC=%#x\n",
diff --git a/xen/arch/x86/include/asm/ioreq.h b/xen/arch/x86/include/asm/ioreq.h
index d06ce9a6ea..ecfe7f9fdb 100644
--- a/xen/arch/x86/include/asm/ioreq.h
+++ b/xen/arch/x86/include/asm/ioreq.h
@@ -26,6 +26,9 @@
#include <asm/hvm/ioreq.h>
#endif
+struct arch_vcpu_io {
+};
+
#endif /* __ASM_X86_IOREQ_H__ */
/*
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index 37f78cc4c4..afe5508be8 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -160,6 +160,8 @@ struct vcpu_io {
/* I/O request in flight to device model. */
enum vio_completion completion;
ioreq_t req;
+ /* Arch specific info pertaining to the io request */
+ struct arch_vcpu_io info;
};
struct vcpu
--
2.17.1
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