Re: [Xen-devel] [PATCH] x86/hvm: make hvmemul_virtual_to_linear()'s reps parameter optional
> -Original Message-
> From: Jan Beulich
> Sent: 01 July 2019 13:00
> To: xen-devel@lists.xenproject.org; xen-devel@lists.xenproject.org
> Cc: Andrew Cooper ; Wei Liu ; Roger
> Pau Monne
> ; Paul Durrant
> Subject: [PATCH] x86/hvm: make hvmemul_virtual_to_linear()'s reps parameter
> optional
>
> 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
Reviewed-by: Paul Durrant
> ---
> 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_UNHANDLEA
Re: [Xen-devel] [PATCH] x86/hvm: make hvmemul_virtual_to_linear()'s reps parameter optional
Useful patch, glad to have it on the table. On 01.07.2019 14:59, 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 Reviewed-by: Alexandru Isaila > --- > Note that this conflicts with additions/changes made by "x86emul: > further work". Whatever goes in later will need re-basing. > ___ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
[Xen-devel] [PATCH] x86/hvm: make hvmemul_virtual_to_linear()'s reps parameter optional
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
---
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_ct
