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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [xen staging] xen/arm64: io: Emulate instructions (with invalid ISS) on MMIO region
commit 5e9c429ad41f03740817ed370119f9f9f2a3a68f
Author: Ayan Kumar Halder <ayan.kumar.halder@xxxxxxxxxx>
AuthorDate: Thu Mar 17 14:00:44 2022 +0000
Commit: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
CommitDate: Fri Mar 18 21:17:13 2022 -0700
xen/arm64: io: Emulate instructions (with invalid ISS) on MMIO region
When an instruction is trapped in Xen due to translation fault, Xen
checks if the ISS is invalid (for data abort) or it is an instruction
abort. If so, Xen tries to resolve the translation fault using p2m page
tables. In case of 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/executing the instruction,
Xen will forward the abort to the guest.
Also, the logic to infer the type of instruction has been moved from
try_handle_mmio() to try_decode_instruction() which is called before.
try_handle_mmio() is solely responsible for handling the mmio operation.
Signed-off-by: Ayan Kumar Halder <ayankuma@xxxxxxxxxx>
Tested-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>
---
xen/arch/arm/arm32/traps.c | 12 ++++++
xen/arch/arm/arm64/traps.c | 52 ++++++++++++++++++++++
xen/arch/arm/decode.c | 2 +
xen/arch/arm/include/asm/domain.h | 4 ++
xen/arch/arm/include/asm/mmio.h | 17 +++++++-
xen/arch/arm/include/asm/traps.h | 2 +
xen/arch/arm/io.c | 90 ++++++++++++++++++++++++---------------
xen/arch/arm/ioreq.c | 8 +++-
xen/arch/arm/traps.c | 77 ++++++++++++++++++++++++++-------
xen/arch/x86/include/asm/domain.h | 3 ++
xen/include/xen/sched.h | 2 +
11 files changed, 215 insertions(+), 54 deletions(-)
diff --git a/xen/arch/arm/arm32/traps.c b/xen/arch/arm/arm32/traps.c
index 9c9790a6d1..a4ce2b92d9 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 +84,16 @@ void do_trap_data_abort(struct cpu_user_regs *regs)
do_unexpected_trap("Data Abort", regs);
}
+void finalize_instr_emulation(const struct instr_details *instr)
+{
+ /*
+ * We have not implemented decoding of post indexing instructions for 32
bit.
+ * Thus, this should be unreachable.
+ */
+ if ( instr->state == INSTR_LDR_STR_POSTINDEXING )
+ 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..3f8858acec 100644
--- a/xen/arch/arm/arm64/traps.c
+++ b/xen/arch/arm/arm64/traps.c
@@ -17,6 +17,7 @@
*/
#include <xen/lib.h>
+#include <xen/sched.h>
#include <asm/hsr.h>
#include <asm/system.h>
@@ -44,6 +45,57 @@ void do_bad_mode(struct cpu_user_regs *regs, int reason)
panic("bad mode\n");
}
+void finalize_instr_emulation(const struct instr_details *instr)
+{
+ struct cpu_user_regs *regs = guest_cpu_user_regs();
+ register_t val = 0;
+ uint8_t psr_mode = (regs->cpsr & PSR_MODE_MASK);
+
+ /* 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 )
+ {
+ switch ( psr_mode )
+ {
+ case PSR_MODE_EL1h:
+ val = regs->sp_el1;
+ break;
+ case PSR_MODE_EL1t:
+ case PSR_MODE_EL0t:
+ val = regs->sp_el0;
+ break;
+
+ default:
+ 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 3add87e83a..f5f6562600 100644
--- a/xen/arch/arm/decode.c
+++ b/xen/arch/arm/decode.c
@@ -146,8 +146,10 @@ 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;
+ dabt->valid = 1;
return 0;
diff --git a/xen/arch/arm/include/asm/domain.h
b/xen/arch/arm/include/asm/domain.h
index c56f6e4398..ed63c2b6f9 100644
--- a/xen/arch/arm/include/asm/domain.h
+++ b/xen/arch/arm/include/asm/domain.h
@@ -281,6 +281,10 @@ 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..ca259a79c2 100644
--- a/xen/arch/arm/include/asm/mmio.h
+++ b/xen/arch/arm/include/asm/mmio.h
@@ -26,12 +26,24 @@
#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 */
+ /*
+ * Instruction is decoded successfully. It is a ldr/str post indexing
+ * instruction.
+ */
+ INSTR_LDR_STR_POSTINDEXING,
+};
+
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 +81,15 @@ 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..08bc0b484c 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 finalize_instr_emulation(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 fad103bdbd..fd903b7b03 100644
--- a/xen/arch/arm/io.c
+++ b/xen/arch/arm/io.c
@@ -102,57 +102,79 @@ 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;
+
+ if ( info->dabt.valid )
+ {
+ info->dabt_instr.state = INSTR_VALID;
+
+ /*
+ * 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;
+ }
+
+ /*
+ * 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);
- if ( !handler )
+ if ( !info->dabt.valid )
{
- int rc;
+ ASSERT_UNREACHABLE();
+ return IO_ABORT;
+ }
- rc = try_fwd_ioserv(regs, v, &info);
+ handler = find_mmio_handler(v->domain, info->gpa);
+ if ( !handler )
+ {
+ 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 )
+ return handle_write(handler, v, info);
else
- return handle_read(handler, v, &info);
+ return handle_read(handler, v, info);
}
void register_mmio_handler(struct domain *d,
diff --git a/xen/arch/arm/ioreq.c b/xen/arch/arm/ioreq.c
index 308650b400..54167aebcb 100644
--- a/xen/arch/arm/ioreq.c
+++ b/xen/arch/arm/ioreq.c
@@ -47,6 +47,8 @@ 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 instr_details instr = info->dabt_instr;
+ struct hsr_dabt dabt = info->dabt;
ioreq_t p = {
.type = IOREQ_TYPE_COPY,
.addr = info->gpa,
@@ -76,10 +78,10 @@ enum io_state try_fwd_ioserv(struct cpu_user_regs *regs,
if ( !s )
return IO_UNHANDLED;
- if ( !info->dabt.valid )
- return IO_ABORT;
+ ASSERT(dabt.valid);
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 +97,7 @@ 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 +109,7 @@ bool arch_ioreq_complete_mmio(void)
if ( handle_ioserv(regs, v) == IO_HANDLED )
{
+ finalize_instr_emulation(&dabt_instr);
advance_pc(regs, hsr);
return true;
}
diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 7a1b679b8c..11f970d926 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 +1921,8 @@ 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;
+ enum io_state state;
/*
* If this bit has been set, it means that this stage-2 abort is caused
@@ -1959,21 +1976,52 @@ static void do_trap_stage2_abort_guest(struct
cpu_user_regs *regs,
return;
}
case FSC_FLT_TRANS:
+ {
+ info.gpa = gpa;
+ info.dabt = hsr.dabt;
+
/*
- * Attempt first to emulate the MMIO as the data abort will
- * likely happen in an emulated region.
- *
- * Note that emulated region cannot be executed
+ * Assumption :- Most of the times when we get a data abort and the ISS
+ * is invalid or an instruction abort, the underlying cause is that the
+ * page tables have not been set up correctly.
*/
- if ( is_data )
+ if ( !is_data || !info.dabt.valid )
{
- enum io_state state = try_handle_mmio(regs, hsr, gpa);
+ if ( check_p2m(is_data, gpa) )
+ return;
- switch ( state )
- {
+ /*
+ * If the instruction abort could not be resolved by setting the
+ * appropriate bits in the translation table, then Xen should
+ * forward the abort to the guest.
+ */
+ if ( !is_data )
+ goto inject_abt;
+ }
+
+ try_decode_instruction(regs, &info);
+
+ /*
+ * If Xen could not decode the instruction or encountered an error
+ * while decoding, then it should forward the abort to the guest.
+ */
+ if ( info.dabt_instr.state == INSTR_ERROR )
+ 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.
+ */
+ finalize_instr_emulation(&info.dabt_instr);
advance_pc(regs, hsr);
return;
case IO_RETRY:
@@ -1982,21 +2030,18 @@ static void do_trap_stage2_abort_guest(struct
cpu_user_regs *regs,
case IO_UNHANDLED:
/* IO unhandled, try another way to handle it. */
break;
- }
}
/*
- * First check if the translation fault can be resolved by the
- * P2M subsystem. If that's the case nothing else to do.
+ * If the instruction syndrome was invalid, then we already checked if
+ * this was due to a P2M fault. So no point to check again as the
result
+ * will be the same.
*/
- if ( p2m_resolve_translation_fault(current->domain,
- gaddr_to_gfn(gpa)) )
- return;
-
- if ( is_data && try_map_mmio(gaddr_to_gfn(gpa)) )
+ if ( (info.dabt_instr.state == INSTR_VALID) && 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/domain.h
b/xen/arch/x86/include/asm/domain.h
index e62e109598..35898d725f 100644
--- a/xen/arch/x86/include/asm/domain.h
+++ b/xen/arch/x86/include/asm/domain.h
@@ -756,6 +756,9 @@ static inline void pv_inject_sw_interrupt(unsigned int
vector)
: is_pv_32bit_domain(d) ? PV32_VM_ASSIST_MASK \
: PV64_VM_ASSIST_MASK)
+struct arch_vcpu_io {
+};
+
#endif /* __ASM_DOMAIN_H__ */
/*
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index 10ea969c7a..406d9bc610 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
--
generated by git-patchbot for /home/xen/git/xen.git#staging
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