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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 2/2] x86/vm_event: Allow returning i-cache for emulation
On 09/15/16 19:36, Tamas K Lengyel wrote:
> On Wed, Sep 14, 2016 at 1:58 AM, Razvan Cojocaru
> <rcojocaru@xxxxxxxxxxxxxxx> wrote:
>> On 09/13/2016 09:12 PM, Tamas K Lengyel wrote:
>>> When emulating instructions the emulator maintains a small i-cache fetched
>>> from the guest memory. This patch extends the vm_event interface to allow
>>> returning this i-cache via the vm_event response instead.
>>>
>>> When responding to a SOFTWARE_BREAKPOINT event (INT3) the monitor subscriber
>>> normally has to remove the INT3 from memory - singlestep - place back INT3
>>> to allow the guest to continue execution. This routine however is
>>> susceptible
>>> to a race-condition on multi-vCPU guests. By allowing the subscriber to
>>> return
>>> the i-cache to be used for emulation it can side-step the problem by
>>> returning
>>> a clean buffer without the INT3 present.
>>>
>>> As part of this patch we rename hvm_mem_access_emulate_one to
>>> hvm_emulate_one_vm_event to better reflect that it is used in various
>>> vm_event
>>> scenarios now, not just in response to mem_access events.
>>>
>>> Signed-off-by: Tamas K Lengyel <tamas.lengyel@xxxxxxxxxxxx>
>>> ---
>>> Cc: Paul Durrant <paul.durrant@xxxxxxxxxx>
>>> Cc: Jan Beulich <jbeulich@xxxxxxxx>
>>> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>>> Cc: Jun Nakajima <jun.nakajima@xxxxxxxxx>
>>> Cc: Kevin Tian <kevin.tian@xxxxxxxxx>
>>> Cc: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
>>> Cc: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
>>> Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
>>> Cc: Julien Grall <julien.grall@xxxxxxx>
>>>
>>> Note: This patch only has been compile-tested.
>>> ---
>>> xen/arch/x86/hvm/emulate.c | 44
>>> ++++++++++++++++++++++++++-------------
>>> xen/arch/x86/hvm/hvm.c | 9 +++++---
>>> xen/arch/x86/hvm/vmx/vmx.c | 1 +
>>> xen/arch/x86/vm_event.c | 9 +++++++-
>>> xen/common/vm_event.c | 1 -
>>> xen/include/asm-x86/hvm/emulate.h | 8 ++++---
>>> xen/include/asm-x86/vm_event.h | 3 ++-
>>> xen/include/public/vm_event.h | 16 +++++++++++++-
>>> 8 files changed, 67 insertions(+), 24 deletions(-)
>>>
>>> diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c
>>> index cc25676..504ed35 100644
>>> --- a/xen/arch/x86/hvm/emulate.c
>>> +++ b/xen/arch/x86/hvm/emulate.c
>>> @@ -76,9 +76,9 @@ static int set_context_data(void *buffer, unsigned int
>>> size)
>>> if ( curr->arch.vm_event )
>>> {
>>> unsigned int safe_size =
>>> - min(size, curr->arch.vm_event->emul_read_data.size);
>>> + min(size, curr->arch.vm_event->emul_read.size);
>>>
>>> - memcpy(buffer, curr->arch.vm_event->emul_read_data.data,
>>> safe_size);
>>> + memcpy(buffer, curr->arch.vm_event->emul_read.data, safe_size);
>>> memset(buffer + safe_size, 0, size - safe_size);
>>> return X86EMUL_OKAY;
>>> }
>>> @@ -827,7 +827,7 @@ static int hvmemul_read(
>>> struct hvm_emulate_ctxt *hvmemul_ctxt =
>>> container_of(ctxt, struct hvm_emulate_ctxt, ctxt);
>>>
>>> - if ( unlikely(hvmemul_ctxt->set_context) )
>>> + if ( unlikely(hvmemul_ctxt->set_context_data) )
>>> return set_context_data(p_data, bytes);
>>>
>>> return __hvmemul_read(
>>> @@ -1029,7 +1029,7 @@ static int hvmemul_cmpxchg(
>>> struct hvm_emulate_ctxt *hvmemul_ctxt =
>>> container_of(ctxt, struct hvm_emulate_ctxt, ctxt);
>>>
>>> - if ( unlikely(hvmemul_ctxt->set_context) )
>>> + if ( unlikely(hvmemul_ctxt->set_context_data) )
>>> {
>>> int rc = set_context_data(p_new, bytes);
>>>
>>> @@ -1122,7 +1122,7 @@ static int hvmemul_rep_outs(
>>> p2m_type_t p2mt;
>>> int rc;
>>>
>>> - if ( unlikely(hvmemul_ctxt->set_context) )
>>> + if ( unlikely(hvmemul_ctxt->set_context_data) )
>>> return hvmemul_rep_outs_set_context(src_seg, src_offset, dst_port,
>>> bytes_per_rep, reps, ctxt);
>>>
>>> @@ -1264,7 +1264,7 @@ static int hvmemul_rep_movs(
>>> if ( buf == NULL )
>>> return X86EMUL_UNHANDLEABLE;
>>>
>>> - if ( unlikely(hvmemul_ctxt->set_context) )
>>> + if ( unlikely(hvmemul_ctxt->set_context_data) )
>>> {
>>> rc = set_context_data(buf, bytes);
>>>
>>> @@ -1470,7 +1470,7 @@ static int hvmemul_read_io(
>>>
>>> *val = 0;
>>>
>>> - if ( unlikely(hvmemul_ctxt->set_context) )
>>> + if ( unlikely(hvmemul_ctxt->set_context_data) )
>>> return set_context_data(val, bytes);
>>>
>>> return hvmemul_do_pio_buffer(port, bytes, IOREQ_READ, val);
>>> @@ -1793,7 +1793,14 @@ static int _hvm_emulate_one(struct hvm_emulate_ctxt
>>> *hvmemul_ctxt,
>>> pfec |= PFEC_user_mode;
>>>
>>> hvmemul_ctxt->insn_buf_eip = regs->eip;
>>> - if ( !vio->mmio_insn_bytes )
>>> +
>>> + if ( unlikely(hvmemul_ctxt->set_context_insn) && curr->arch.vm_event )
>>> + {
>>> + hvmemul_ctxt->insn_buf_bytes =
>>> sizeof(curr->arch.vm_event->emul_insn);
>>> + memcpy(hvmemul_ctxt->insn_buf, &curr->arch.vm_event->emul_insn,
>>> + hvmemul_ctxt->insn_buf_bytes);
>>> + }
>>> + else if ( !vio->mmio_insn_bytes )
>>> {
>>> hvmemul_ctxt->insn_buf_bytes =
>>> hvm_get_insn_bytes(curr, hvmemul_ctxt->insn_buf) ?:
>>> @@ -1931,7 +1938,7 @@ int hvm_emulate_one_mmio(unsigned long mfn, unsigned
>>> long gla)
>>> return rc;
>>> }
>>>
>>> -void hvm_mem_access_emulate_one(enum emul_kind kind, unsigned int trapnr,
>>> +void hvm_emulate_one_vm_event(enum emul_kind kind, unsigned int trapnr,
>>> unsigned int errcode)
>>> {
>>> struct hvm_emulate_ctxt ctx = {{ 0 }};
>>> @@ -1944,11 +1951,19 @@ void hvm_mem_access_emulate_one(enum emul_kind
>>> kind, unsigned int trapnr,
>>> case EMUL_KIND_NOWRITE:
>>> rc = hvm_emulate_one_no_write(&ctx);
>>> break;
>>> - case EMUL_KIND_SET_CONTEXT:
>>> - ctx.set_context = 1;
>>> - /* Intentional fall-through. */
>>> - default:
>>> + case EMUL_KIND_SET_CONTEXT_DATA:
>>> + ctx.set_context_data = 1;
>>> + rc = hvm_emulate_one(&ctx);
>>> + break;
>>> + case EMUL_KIND_SET_CONTEXT_INSN:
>>> + ctx.set_context_insn = 1;
>>> rc = hvm_emulate_one(&ctx);
>>> + break;
>>> + case EMUL_KIND_NORMAL:
>>> + rc = hvm_emulate_one(&ctx);
>>> + break;
>>> + default:
>>> + return;
>>> }
>>>
>>> switch ( rc )
>>> @@ -1983,7 +1998,8 @@ void hvm_emulate_prepare(
>>> hvmemul_ctxt->ctxt.force_writeback = 1;
>>> hvmemul_ctxt->seg_reg_accessed = 0;
>>> hvmemul_ctxt->seg_reg_dirty = 0;
>>> - hvmemul_ctxt->set_context = 0;
>>> + hvmemul_ctxt->set_context_data = 0;
>>> + hvmemul_ctxt->set_context_insn = 0;
>>> hvmemul_get_seg_reg(x86_seg_cs, hvmemul_ctxt);
>>> hvmemul_get_seg_reg(x86_seg_ss, hvmemul_ctxt);
>>> }
>>> diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
>>> index ca96643..7462794 100644
>>> --- a/xen/arch/x86/hvm/hvm.c
>>> +++ b/xen/arch/x86/hvm/hvm.c
>>> @@ -489,13 +489,16 @@ void hvm_do_resume(struct vcpu *v)
>>>
>>> if ( v->arch.vm_event->emulate_flags &
>>> VM_EVENT_FLAG_SET_EMUL_READ_DATA )
>>> - kind = EMUL_KIND_SET_CONTEXT;
>>> + kind = EMUL_KIND_SET_CONTEXT_DATA;
>>> else if ( v->arch.vm_event->emulate_flags &
>>> VM_EVENT_FLAG_EMULATE_NOWRITE )
>>> kind = EMUL_KIND_NOWRITE;
>>> + else if ( v->arch.vm_event->emulate_flags &
>>> + VM_EVENT_FLAG_SET_EMUL_INSN_DATA )
>>> + kind = EMUL_KIND_SET_CONTEXT_INSN;
>>>
>>> - hvm_mem_access_emulate_one(kind, TRAP_invalid_op,
>>> - HVM_DELIVER_NO_ERROR_CODE);
>>> + hvm_emulate_one_vm_event(kind, TRAP_invalid_op,
>>> + HVM_DELIVER_NO_ERROR_CODE);
>>>
>>> v->arch.vm_event->emulate_flags = 0;
>>> }
>>> diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
>>> index 2759e6f..d214716 100644
>>> --- a/xen/arch/x86/hvm/vmx/vmx.c
>>> +++ b/xen/arch/x86/hvm/vmx/vmx.c
>>> @@ -57,6 +57,7 @@
>>> #include <asm/altp2m.h>
>>> #include <asm/event.h>
>>> #include <asm/monitor.h>
>>> +#include <asm/vm_event.h>
>>> #include <public/arch-x86/cpuid.h>
>>>
>>> static bool_t __initdata opt_force_ept;
>>> diff --git a/xen/arch/x86/vm_event.c b/xen/arch/x86/vm_event.c
>>> index 343b9c8..03beed3 100644
>>> --- a/xen/arch/x86/vm_event.c
>>> +++ b/xen/arch/x86/vm_event.c
>>> @@ -209,11 +209,18 @@ void vm_event_emulate_check(struct vcpu *v,
>>> vm_event_response_t *rsp)
>>> if ( p2m_mem_access_emulate_check(v, rsp) )
>>> {
>>> if ( rsp->flags & VM_EVENT_FLAG_SET_EMUL_READ_DATA )
>>> - v->arch.vm_event->emul_read_data =
>>> rsp->data.emul_read_data;
>>> + v->arch.vm_event->emul_read = rsp->data.emul.read;
>>>
>>> v->arch.vm_event->emulate_flags = rsp->flags;
>>> }
>>> break;
>>> + case VM_EVENT_REASON_SOFTWARE_BREAKPOINT:
>>> + if ( rsp->flags & VM_EVENT_FLAG_SET_EMUL_INSN_DATA )
>>> + {
>>> + v->arch.vm_event->emul_insn = rsp->data.emul.insn;
>>> + v->arch.vm_event->emulate_flags = rsp->flags;
>>> + }
>>> + break;
>>> default:
>>> break;
>>> };
>>> diff --git a/xen/common/vm_event.c b/xen/common/vm_event.c
>>> index 907ab40..d8ee7f3 100644
>>> --- a/xen/common/vm_event.c
>>> +++ b/xen/common/vm_event.c
>>> @@ -398,7 +398,6 @@ void vm_event_resume(struct domain *d, struct
>>> vm_event_domain *ved)
>>> * In some cases the response type needs extra handling, so here
>>> * we call the appropriate handlers.
>>> */
>>> -
>>> /* Check flags which apply only when the vCPU is paused */
>>> if ( atomic_read(&v->vm_event_pause_count) )
>>> {
>>> diff --git a/xen/include/asm-x86/hvm/emulate.h
>>> b/xen/include/asm-x86/hvm/emulate.h
>>> index 3aabcbe..b52f99e 100644
>>> --- a/xen/include/asm-x86/hvm/emulate.h
>>> +++ b/xen/include/asm-x86/hvm/emulate.h
>>> @@ -34,20 +34,22 @@ struct hvm_emulate_ctxt {
>>>
>>> uint32_t intr_shadow;
>>>
>>> - bool_t set_context;
>>> + bool_t set_context_data;
>>> + bool_t set_context_insn;
>>> };
>>>
>>> enum emul_kind {
>>> EMUL_KIND_NORMAL,
>>> EMUL_KIND_NOWRITE,
>>> - EMUL_KIND_SET_CONTEXT
>>> + EMUL_KIND_SET_CONTEXT_DATA,
>>> + EMUL_KIND_SET_CONTEXT_INSN
>>
>> Since this breaks compilation of existing clients, I think we should
>> increment some macro to alow for compile-time switching (maybe
>> VM_EVENT_INTERFACE_VERSION?).
>
> I'm not sure I follow - this is a Xen internal-only enumeration. What
> kind-of clients are you referring to?
Nevermind, I thought these changes propagate to the toolstack headers.
Sorry for the confusion.
Thanks,
Razvan
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