| Message ID | 20220310174501.62040-3-ayankuma@xilinx.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | xen/arm64: io: Decode ldr/str post-indexing instruction | expand |
On Thu, 10 Mar 2022, Ayan Kumar Halder wrote: > 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@xilinx.com> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org> > --- > > 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. > > > v9 - 1. Ensure that "Erratum 766422" is handled only when ISS is valid. > > 2. Whenever Xen receives and instruction abort or data abort (with invalid ISS), > Xen should first try to resolve the p2m translation fault or see if it it needs > to map a MMIO region. If it succeeds, it should return to the guest to retry the > instruction. > > 3. Removed handling of "dabt.s1ptw == 1" aborts. This is addressed in patch3 as > it is an existing bug in codebase. > > 4. Various style issues pointed by Julien in v8. > > > v10 - 1. Set 'dabt.valid=1' when the instruction is fully decoded. This is > checked in try_handle_mmio() and try_fwd_ioserv(). > > 2. Various other style issues pointed in v9. > > xen/arch/arm/arm32/traps.c | 11 ++++ > 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/ioreq.h | 3 ++ > xen/include/xen/sched.h | 2 + > 11 files changed, 214 insertions(+), 54 deletions(-) > > diff --git a/xen/arch/arm/arm32/traps.c b/xen/arch/arm/arm32/traps.c > index 9c9790a6d1..159e3cef8b 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 +84,15 @@ 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) > +{ > + /* > + * We have not implemented decoding of post indexing instructions for 32 bit. > + * Thus, this should be unreachable. > + */ > + 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..6ce4a1fa8c 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 post_increment_register(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..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 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..cc9bf23213 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 ) > { > + 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 7a1b679b8c..53652d7781 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. > + */ > + post_increment_register(&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/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 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 > -- > 2.17.1 > >
Hi, On 10/03/2022 17:44, Ayan Kumar Halder wrote: > 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@xilinx.com> Acked-by: Julien Grall <jgrall@amazon.com> Cheers,
Hi Ayan, On 10/03/2022 17:44, Ayan Kumar Halder wrote: > diff --git a/xen/arch/arm/arm32/traps.c b/xen/arch/arm/arm32/traps.c > index 9c9790a6d1..159e3cef8b 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 +84,15 @@ 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) > +{ > + /* > + * We have not implemented decoding of post indexing instructions for 32 bit. > + * Thus, this should be unreachable. > + */ > + domain_crash(current->domain); Osstest [1] is reporting a crash here. This is because post_increment_register() is called unconditionally. I think you need to add: if ( instr->state != INSTR_LDR_STR_POSTINDEXING ) Also, given this is called unconditionally, I think the function needs to be renamed to some more generic. Maybe finalize_instr_emulation() or similar. I have decided to revert this patch and patch #3 for now. Please test it on arm32 and respin it. While you are at it, please make sure the title is no longer than 80 characters. Cheers, > +} > + [1] http://logs.test-lab.xenproject.org/osstest/logs/168589/test-armhf-armhf-xl/info.html
On 10.03.2022 18:44, Ayan Kumar Halder wrote: > 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@xilinx.com> In addition to the boot crash on 32-bit Arm there's also an early build failure on x86: In file included from arch/x86/x86_64/asm-offsets.c:11: ./include/xen/sched.h:164:26: error: field 'info' has incomplete type struct arch_vcpu_io info; ^~~~ Note how on Arm you have ... > --- 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 */ > +}; ... this in asm/domain.h, and thus visible to xen/sched.h, while on x86 you have ... > --- 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 { > +}; ... this in a header which xen/sched.h doesn't end up including. I would like to ask that you arrange locally for at least an x86 build test whenever you touch code which might also affect x86. Jan
diff --git a/xen/arch/arm/arm32/traps.c b/xen/arch/arm/arm32/traps.c index 9c9790a6d1..159e3cef8b 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 +84,15 @@ 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) +{ + /* + * We have not implemented decoding of post indexing instructions for 32 bit. + * Thus, this should be unreachable. + */ + 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..6ce4a1fa8c 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 post_increment_register(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..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 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..cc9bf23213 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 ) { + 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 7a1b679b8c..53652d7781 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. + */ + post_increment_register(&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/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 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
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@xilinx.com> --- 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. v9 - 1. Ensure that "Erratum 766422" is handled only when ISS is valid. 2. Whenever Xen receives and instruction abort or data abort (with invalid ISS), Xen should first try to resolve the p2m translation fault or see if it it needs to map a MMIO region. If it succeeds, it should return to the guest to retry the instruction. 3. Removed handling of "dabt.s1ptw == 1" aborts. This is addressed in patch3 as it is an existing bug in codebase. 4. Various style issues pointed by Julien in v8. v10 - 1. Set 'dabt.valid=1' when the instruction is fully decoded. This is checked in try_handle_mmio() and try_fwd_ioserv(). 2. Various other style issues pointed in v9. xen/arch/arm/arm32/traps.c | 11 ++++ 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/ioreq.h | 3 ++ xen/include/xen/sched.h | 2 + 11 files changed, 214 insertions(+), 54 deletions(-)