On 01.07.2019 13:59, Jan Beulich wrote:
> A majority of callers wants just a single iteration handled. Allow to
> express this by passing in a NULL pointer, instead of setting up a local
> variable just to hold the "1" to pass in here.
>
> Signed-off-by: Jan Beulich <jbeul...@suse.com>
> ---
> Note that this conflicts with additions/changes made by "x86emul:
> further work". Whatever goes in later will need re-basing.
>
> --- a/xen/arch/x86/hvm/emulate.c
> +++ b/xen/arch/x86/hvm/emulate.c
> @@ -788,14 +788,14 @@ static int hvmemul_virtual_to_linear(
> enum x86_segment seg,
> unsigned long offset,
> unsigned int bytes_per_rep,
> - unsigned long *reps,
> + unsigned long *reps_p,
> enum hvm_access_type access_type,
> struct hvm_emulate_ctxt *hvmemul_ctxt,
> unsigned long *linear)
> {
> struct segment_register *reg;
> int okay;
> - unsigned long max_reps = 4096;
> + unsigned long reps = 1;
>
> if ( seg == x86_seg_none )
> {
> @@ -803,62 +803,72 @@ static int hvmemul_virtual_to_linear(
> return X86EMUL_OKAY;
> }
>
> - /*
> - * If introspection has been enabled for this domain, and we're emulating
> - * becase a vm_reply asked us to (i.e. not doing regular IO) reps should
> - * be at most 1, since optimization might otherwise cause a single
> - * vm_event being triggered for repeated writes to a whole page.
> - */
> - if ( unlikely(current->domain->arch.mem_access_emulate_each_rep) &&
> - current->arch.vm_event->emulate_flags != 0 )
> - max_reps = 1;
> + if ( reps_p )
> + {
> + unsigned long max_reps = 4096;
>
> - /*
> - * Clip repetitions to avoid overflow when multiplying by @bytes_per_rep.
> - * The chosen maximum is very conservative but it's what we use in
> - * hvmemul_linear_to_phys() so there is no point in using a larger value.
> - */
> - *reps = min_t(unsigned long, *reps, max_reps);
> + /*
> + * If introspection has been enabled for this domain, and we're
> + * emulating because a vm_reply asked us to (i.e. not doing regular
> IO)
> + * reps should be at most 1, since optimization might otherwise
> cause a
> + * single vm_event being triggered for repeated writes to a whole
> page.
> + */
> + if ( unlikely(current->domain->arch.mem_access_emulate_each_rep) &&
> + current->arch.vm_event->emulate_flags != 0 )
> + max_reps = 1;
> +
> + /*
> + * Clip repetitions to avoid overflow when multiplying by
> + * @bytes_per_rep. The chosen maximum is very conservative but it's
> + * what we use in hvmemul_linear_to_phys() so there is no point in
> + * using a larger value.
> + */
> + reps = *reps_p = min_t(unsigned long, *reps_p, max_reps);
> + }
>
> reg = hvmemul_get_seg_reg(seg, hvmemul_ctxt);
> if ( IS_ERR(reg) )
> return -PTR_ERR(reg);
>
> - if ( (hvmemul_ctxt->ctxt.regs->eflags & X86_EFLAGS_DF) && (*reps > 1) )
> + if ( (hvmemul_ctxt->ctxt.regs->eflags & X86_EFLAGS_DF) && (reps > 1) )
> {
> /*
> * x86_emulate() clips the repetition count to ensure we don't wrap
> * the effective-address index register. Hence this assertion
> holds.
> */
> - ASSERT(offset >= ((*reps - 1) * bytes_per_rep));
> + ASSERT(offset >= ((reps - 1) * bytes_per_rep));
> okay = hvm_virtual_to_linear_addr(
> - seg, reg, offset - (*reps - 1) * bytes_per_rep,
> - *reps * bytes_per_rep, access_type,
> + seg, reg, offset - (reps - 1) * bytes_per_rep,
> + reps * bytes_per_rep, access_type,
> hvmemul_get_seg_reg(x86_seg_cs, hvmemul_ctxt), linear);
> - *linear += (*reps - 1) * bytes_per_rep;
> + *linear += (reps - 1) * bytes_per_rep;
> if ( hvmemul_ctxt->ctxt.addr_size != 64 )
> *linear = (uint32_t)*linear;
> }
> else
> {
> okay = hvm_virtual_to_linear_addr(
> - seg, reg, offset, *reps * bytes_per_rep, access_type,
> + seg, reg, offset, reps * bytes_per_rep, access_type,
> hvmemul_get_seg_reg(x86_seg_cs, hvmemul_ctxt), linear);
> }
>
> if ( okay )
> return X86EMUL_OKAY;
>
> - /* If this is a string operation, emulate each iteration separately. */
> - if ( *reps != 1 )
> - return X86EMUL_UNHANDLEABLE;
> + if ( reps_p )
> + {
> + /* If this is a string operation, emulate each iteration separately.
> */
> + if ( reps != 1 )
> + return X86EMUL_UNHANDLEABLE;
> +
> + *reps_p = 0;
> + }
>
> /*
> * Leave exception injection to the caller for non-user segments: We
> * neither know the exact error code to be used, nor can we easily
> * determine the kind of exception (#GP or #TS) in that case.
> */
> - *reps = 0;
> if ( is_x86_user_segment(seg) )
> x86_emul_hw_exception((seg == x86_seg_ss)
> ? TRAP_stack_error
> @@ -1201,7 +1211,7 @@ static int __hvmemul_read(
> enum hvm_access_type access_type,
> struct hvm_emulate_ctxt *hvmemul_ctxt)
> {
> - unsigned long addr, reps = 1;
> + unsigned long addr;
> uint32_t pfec = PFEC_page_present;
> int rc;
>
> @@ -1213,7 +1223,7 @@ static int __hvmemul_read(
> pfec |= PFEC_insn_fetch;
>
> rc = hvmemul_virtual_to_linear(
> - seg, offset, bytes, &reps, access_type, hvmemul_ctxt, &addr);
> + seg, offset, bytes, NULL, access_type, hvmemul_ctxt, &addr);
> if ( rc != X86EMUL_OKAY || !bytes )
> return rc;
>
> @@ -1294,7 +1304,7 @@ static int hvmemul_write(
> {
> struct hvm_emulate_ctxt *hvmemul_ctxt =
> container_of(ctxt, struct hvm_emulate_ctxt, ctxt);
> - unsigned long addr, reps = 1;
> + unsigned long addr;
> uint32_t pfec = PFEC_page_present | PFEC_write_access;
> int rc;
> void *mapping = NULL;
> @@ -1305,7 +1315,7 @@ static int hvmemul_write(
> pfec |= PFEC_user_mode;
>
> rc = hvmemul_virtual_to_linear(
> - seg, offset, bytes, &reps, hvm_access_write, hvmemul_ctxt, &addr);
> + seg, offset, bytes, NULL, hvm_access_write, hvmemul_ctxt, &addr);
> if ( rc != X86EMUL_OKAY || !bytes )
> return rc;
>
> @@ -1336,13 +1346,13 @@ static int hvmemul_rmw(
> {
> struct hvm_emulate_ctxt *hvmemul_ctxt =
> container_of(ctxt, struct hvm_emulate_ctxt, ctxt);
> - unsigned long addr, reps = 1;
> + unsigned long addr;
> uint32_t pfec = PFEC_page_present | PFEC_write_access;
> int rc;
> void *mapping = NULL;
>
> rc = hvmemul_virtual_to_linear(
> - seg, offset, bytes, &reps, hvm_access_write, hvmemul_ctxt, &addr);
> + seg, offset, bytes, NULL, hvm_access_write, hvmemul_ctxt, &addr);
> if ( rc != X86EMUL_OKAY || !bytes )
> return rc;
>
> @@ -1491,14 +1501,14 @@ static int hvmemul_cmpxchg(
> struct hvm_emulate_ctxt *hvmemul_ctxt =
> container_of(ctxt, struct hvm_emulate_ctxt, ctxt);
> struct vcpu *curr = current;
> - unsigned long addr, reps = 1;
> + unsigned long addr;
> uint32_t pfec = PFEC_page_present | PFEC_write_access;
> struct hvm_vcpu_io *vio = &curr->arch.hvm.hvm_io;
> int rc;
> void *mapping = NULL;
>
> rc = hvmemul_virtual_to_linear(
> - seg, offset, bytes, &reps, hvm_access_write, hvmemul_ctxt, &addr);
> + seg, offset, bytes, NULL, hvm_access_write, hvmemul_ctxt, &addr);
> if ( rc != X86EMUL_OKAY )
> return rc;
>
> @@ -2292,11 +2302,11 @@ static int hvmemul_invlpg(
> {
> struct hvm_emulate_ctxt *hvmemul_ctxt =
> container_of(ctxt, struct hvm_emulate_ctxt, ctxt);
> - unsigned long addr, reps = 1;
> + unsigned long addr;
> int rc;
>
> rc = hvmemul_virtual_to_linear(
> - seg, offset, 1, &reps, hvm_access_none, hvmemul_ctxt, &addr);
> + seg, offset, 1, NULL, hvm_access_none, hvmemul_ctxt, &addr);
>
> if ( rc == X86EMUL_EXCEPTION )
> {
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