On Fri, Feb 14, 2020 at 10:56:08AM -0500, Qian Cai wrote:
> arch/x86/kvm/emulate.c: In function 'x86_emulate_insn':
> arch/x86/kvm/emulate.c:5686:22: error: cast between incompatible
> function types from 'int (*)(struct x86_emulate_ctxt *)' to 'void
> (*)(struct fastop *)' [-Werror=cast-function-type]
> rc = fastop(ctxt, (fastop_t)ctxt->execute);
>
> Fixes: 3009afc6e39e ("KVM: x86: Use a typedef for fastop functions")
> Signed-off-by: Qian Cai <[email protected]>
> ---
> arch/x86/kvm/emulate.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index ddbc61984227..17ae820cf59d 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -5682,10 +5682,12 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
> ctxt->eflags &= ~X86_EFLAGS_RF;
>
> if (ctxt->execute) {
> - if (ctxt->d & Fastop)
> - rc = fastop(ctxt, (fastop_t)ctxt->execute);
Alternatively, can we do -Wno-cast-function-type? That's a silly warning
IMO.
If not, will either of these work?
rc = fastop(ctxt, (void *)ctxt->execute);
or
rc = fastop(ctxt, (fastop_t)(void *)ctxt->execute);
> - else
> + if (ctxt->d & Fastop) {
> + fastop_t fop = (void *)ctxt->execute;
> + rc = fastop(ctxt, fop);
> + } else {
> rc = ctxt->execute(ctxt);
> + }
> if (rc != X86EMUL_CONTINUE)
> goto done;
> goto writeback;
> --
> 1.8.3.1
>
On Fri, 2020-02-14 at 08:59 -0800, Sean Christopherson wrote:
> On Fri, Feb 14, 2020 at 10:56:08AM -0500, Qian Cai wrote:
> > arch/x86/kvm/emulate.c: In function 'x86_emulate_insn':
> > arch/x86/kvm/emulate.c:5686:22: error: cast between incompatible
> > function types from 'int (*)(struct x86_emulate_ctxt *)' to 'void
> > (*)(struct fastop *)' [-Werror=cast-function-type]
> > rc = fastop(ctxt, (fastop_t)ctxt->execute);
> >
> > Fixes: 3009afc6e39e ("KVM: x86: Use a typedef for fastop functions")
> > Signed-off-by: Qian Cai <[email protected]>
> > ---
> > arch/x86/kvm/emulate.c | 8 +++++---
> > 1 file changed, 5 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> > index ddbc61984227..17ae820cf59d 100644
> > --- a/arch/x86/kvm/emulate.c
> > +++ b/arch/x86/kvm/emulate.c
> > @@ -5682,10 +5682,12 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
> > ctxt->eflags &= ~X86_EFLAGS_RF;
> >
> > if (ctxt->execute) {
> > - if (ctxt->d & Fastop)
> > - rc = fastop(ctxt, (fastop_t)ctxt->execute);
>
> Alternatively, can we do -Wno-cast-function-type? That's a silly warning
> IMO.
I am doing W=1 on linux-next where some of the warnings might be silly but the
recent commit changes all warnings to errors forces me having to silence those
somehow.
>
> If not, will either of these work?
>
> rc = fastop(ctxt, (void *)ctxt->execute);
>
> or
> rc = fastop(ctxt, (fastop_t)(void *)ctxt->execute);
I have no strong preference. I originally thought just to go back the previous
code style where might be more acceptable, but it is up to maintainers.
>
> > - else
> > + if (ctxt->d & Fastop) {
> > + fastop_t fop = (void *)ctxt->execute;
> > + rc = fastop(ctxt, fop);
> > + } else {
> > rc = ctxt->execute(ctxt);
> > + }
> > if (rc != X86EMUL_CONTINUE)
> > goto done;
> > goto writeback;
> > --
> > 1.8.3.1
> >
On Fri, Feb 14, 2020 at 9:08 AM Qian Cai <[email protected]> wrote:
>
> On Fri, 2020-02-14 at 08:59 -0800, Sean Christopherson wrote:
> > On Fri, Feb 14, 2020 at 10:56:08AM -0500, Qian Cai wrote:
> > > arch/x86/kvm/emulate.c: In function 'x86_emulate_insn':
> > > arch/x86/kvm/emulate.c:5686:22: error: cast between incompatible
> > > function types from 'int (*)(struct x86_emulate_ctxt *)' to 'void
> > > (*)(struct fastop *)' [-Werror=cast-function-type]
> > > rc = fastop(ctxt, (fastop_t)ctxt->execute);
> > >
> > > Fixes: 3009afc6e39e ("KVM: x86: Use a typedef for fastop functions")
> > > Signed-off-by: Qian Cai <[email protected]>
> > > ---
> > > arch/x86/kvm/emulate.c | 8 +++++---
> > > 1 file changed, 5 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> > > index ddbc61984227..17ae820cf59d 100644
> > > --- a/arch/x86/kvm/emulate.c
> > > +++ b/arch/x86/kvm/emulate.c
> > > @@ -5682,10 +5682,12 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
> > > ctxt->eflags &= ~X86_EFLAGS_RF;
> > >
> > > if (ctxt->execute) {
> > > - if (ctxt->d & Fastop)
> > > - rc = fastop(ctxt, (fastop_t)ctxt->execute);
> >
> > Alternatively, can we do -Wno-cast-function-type? That's a silly warning
> > IMO.
>
> I am doing W=1 on linux-next where some of the warnings might be silly but the
> recent commit changes all warnings to errors forces me having to silence those
> somehow.
>
> >
> > If not, will either of these work?
> >
> > rc = fastop(ctxt, (void *)ctxt->execute);
> >
> > or
> > rc = fastop(ctxt, (fastop_t)(void *)ctxt->execute);
>
> I have no strong preference. I originally thought just to go back the previous
> code style where might be more acceptable, but it is up to maintainers.
It seems misguided to define a local variable just to get an implicit
cast from (void *) to (fastop_t). Sean's first suggestion gives you
the same implicit cast without the local variable. The second
suggestion makes both casts explicit.
On Fri, 2020-02-14 at 09:40 -0800, Jim Mattson wrote:
> On Fri, Feb 14, 2020 at 9:08 AM Qian Cai <[email protected]> wrote:
> >
> > On Fri, 2020-02-14 at 08:59 -0800, Sean Christopherson wrote:
> > > On Fri, Feb 14, 2020 at 10:56:08AM -0500, Qian Cai wrote:
> > > > arch/x86/kvm/emulate.c: In function 'x86_emulate_insn':
> > > > arch/x86/kvm/emulate.c:5686:22: error: cast between incompatible
> > > > function types from 'int (*)(struct x86_emulate_ctxt *)' to 'void
> > > > (*)(struct fastop *)' [-Werror=cast-function-type]
> > > > rc = fastop(ctxt, (fastop_t)ctxt->execute);
> > > >
> > > > Fixes: 3009afc6e39e ("KVM: x86: Use a typedef for fastop functions")
> > > > Signed-off-by: Qian Cai <[email protected]>
> > > > ---
> > > > arch/x86/kvm/emulate.c | 8 +++++---
> > > > 1 file changed, 5 insertions(+), 3 deletions(-)
> > > >
> > > > diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> > > > index ddbc61984227..17ae820cf59d 100644
> > > > --- a/arch/x86/kvm/emulate.c
> > > > +++ b/arch/x86/kvm/emulate.c
> > > > @@ -5682,10 +5682,12 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
> > > > ctxt->eflags &= ~X86_EFLAGS_RF;
> > > >
> > > > if (ctxt->execute) {
> > > > - if (ctxt->d & Fastop)
> > > > - rc = fastop(ctxt, (fastop_t)ctxt->execute);
> > >
> > > Alternatively, can we do -Wno-cast-function-type? That's a silly warning
> > > IMO.
> >
> > I am doing W=1 on linux-next where some of the warnings might be silly but the
> > recent commit changes all warnings to errors forces me having to silence those
> > somehow.
> >
> > >
> > > If not, will either of these work?
> > >
> > > rc = fastop(ctxt, (void *)ctxt->execute);
> > >
> > > or
> > > rc = fastop(ctxt, (fastop_t)(void *)ctxt->execute);
> >
> > I have no strong preference. I originally thought just to go back the previous
> > code style where might be more acceptable, but it is up to maintainers.
>
> It seems misguided to define a local variable just to get an implicit
> cast from (void *) to (fastop_t). Sean's first suggestion gives you
> the same implicit cast without the local variable. The second
> suggestion makes both casts explicit.
OK, I'll do a v2 using the first suggestion which looks simpler once it passed
compilations.
On 14/02/20 20:14, Qian Cai wrote:
>> It seems misguided to define a local variable just to get an implicit
>> cast from (void *) to (fastop_t). Sean's first suggestion gives you
>> the same implicit cast without the local variable. The second
>> suggestion makes both casts explicit.
>
> OK, I'll do a v2 using the first suggestion which looks simpler once it passed
> compilations.
>
Another interesting possibility is to use an unnamed union of a
(*execute) function pointer and a (*fastop) function pointer.
Paolo
On Fri, Feb 14, 2020 at 08:33:50PM +0100, Paolo Bonzini wrote:
> On 14/02/20 20:14, Qian Cai wrote:
> >> It seems misguided to define a local variable just to get an implicit
> >> cast from (void *) to (fastop_t). Sean's first suggestion gives you
> >> the same implicit cast without the local variable. The second
> >> suggestion makes both casts explicit.
> >
> > OK, I'll do a v2 using the first suggestion which looks simpler once it passed
> > compilations.
> >
>
> Another interesting possibility is to use an unnamed union of a
> (*execute) function pointer and a (*fastop) function pointer.
I considered that when introducing fastop_t. I don't remember why I
didn't go that route. It's entirely possible I completely forgot that
anonymous unions are allowed and thought it would mean changing a bunch
of use sites.
On Fri, 2020-02-14 at 20:33 +0100, Paolo Bonzini wrote:
> On 14/02/20 20:14, Qian Cai wrote:
> > > It seems misguided to define a local variable just to get an implicit
> > > cast from (void *) to (fastop_t). Sean's first suggestion gives you
> > > the same implicit cast without the local variable. The second
> > > suggestion makes both casts explicit.
> >
> > OK, I'll do a v2 using the first suggestion which looks simpler once it passed
> > compilations.
> >
>
> Another interesting possibility is to use an unnamed union of a
> (*execute) function pointer and a (*fastop) function pointer.
>
This?
diff --git a/arch/x86/include/asm/kvm_emulate.h
b/arch/x86/include/asm/kvm_emulate.h
index 03946eb3e2b9..2a8f2bd2e5cf 100644
--- a/arch/x86/include/asm/kvm_emulate.h
+++ b/arch/x86/include/asm/kvm_emulate.h
@@ -292,6 +292,14 @@ enum x86emul_mode {
#define X86EMUL_SMM_MASK (1 << 6)
#define X86EMUL_SMM_INSIDE_NMI_MASK (1 << 7)
+/*
+ * fastop functions are declared as taking a never-defined fastop parameter,
+ * so they can't be called from C directly.
+ */
+struct fastop;
+
+typedef void (*fastop_t)(struct fastop *);
+
struct x86_emulate_ctxt {
const struct x86_emulate_ops *ops;
@@ -324,7 +332,10 @@ struct x86_emulate_ctxt {
struct operand src;
struct operand src2;
struct operand dst;
- int (*execute)(struct x86_emulate_ctxt *ctxt);
+ union {
+ int (*execute)(struct x86_emulate_ctxt *ctxt);
+ fastop_t fop;
+ };
int (*check_perm)(struct x86_emulate_ctxt *ctxt);
/*
* The following six fields are cleared together,
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index ddbc61984227..dd19fb3539e0 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -191,25 +191,6 @@
#define NR_FASTOP (ilog2(sizeof(ulong)) + 1)
#define FASTOP_SIZE 8
-/*
- * fastop functions have a special calling convention:
- *
- * dst: rax (in/out)
- * src: rdx (in/out)
- * src2: rcx (in)
- * flags: rflags (in/out)
- * ex: rsi (in:fastop pointer, out:zero if exception)
- *
- * Moreover, they are all exactly FASTOP_SIZE bytes long, so functions for
- * different operand sizes can be reached by calculation, rather than a jump
- * table (which would be bigger than the code).
- *
- * fastop functions are declared as taking a never-defined fastop parameter,
- * so they can't be called from C directly.
- */
-
-struct fastop;
-
struct opcode {
u64 flags : 56;
u64 intercept : 8;
@@ -311,8 +292,19 @@ static void invalidate_registers(struct x86_emulate_ctxt
*ctxt)
#define ON64(x)
#endif
-typedef void (*fastop_t)(struct fastop *);
-
+/*
+ * fastop functions have a special calling convention:
+ *
+ * dst: rax (in/out)
+ * src: rdx (in/out)
+ * src2: rcx (in)
+ * flags: rflags (in/out)
+ * ex: rsi (in:fastop pointer, out:zero if exception)
+ *
+ * Moreover, they are all exactly FASTOP_SIZE bytes long, so functions for
+ * different operand sizes can be reached by calculation, rather than a jump
+ * table (which would be bigger than the code).
+ */
static int fastop(struct x86_emulate_ctxt *ctxt, fastop_t fop);
#define __FOP_FUNC(name) \
@@ -5683,7 +5675,7 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
if (ctxt->execute) {
if (ctxt->d & Fastop)
- rc = fastop(ctxt, (fastop_t)ctxt->execute);
+ rc = fastop(ctxt, ctxt->fop);
else
rc = ctxt->execute(ctxt);
if (rc != X86EMUL_CONTINUE)
On 17/02/20 15:47, Qian Cai wrote:
> On Fri, 2020-02-14 at 20:33 +0100, Paolo Bonzini wrote:
>> On 14/02/20 20:14, Qian Cai wrote:
>>>> It seems misguided to define a local variable just to get an implicit
>>>> cast from (void *) to (fastop_t). Sean's first suggestion gives you
>>>> the same implicit cast without the local variable. The second
>>>> suggestion makes both casts explicit.
>>>
>>> OK, I'll do a v2 using the first suggestion which looks simpler once it passed
>>> compilations.
>>>
>>
>> Another interesting possibility is to use an unnamed union of a
>> (*execute) function pointer and a (*fastop) function pointer.
>>
>
> This?
Yes, perfect. Can you send it with Signed-off-by and all that?
Thanks,
Paolo
> diff --git a/arch/x86/include/asm/kvm_emulate.h
> b/arch/x86/include/asm/kvm_emulate.h
> index 03946eb3e2b9..2a8f2bd2e5cf 100644
> --- a/arch/x86/include/asm/kvm_emulate.h
> +++ b/arch/x86/include/asm/kvm_emulate.h
> @@ -292,6 +292,14 @@ enum x86emul_mode {
> #define X86EMUL_SMM_MASK (1 << 6)
> #define X86EMUL_SMM_INSIDE_NMI_MASK (1 << 7)
>
> +/*
> + * fastop functions are declared as taking a never-defined fastop parameter,
> + * so they can't be called from C directly.
> + */
> +struct fastop;
> +
> +typedef void (*fastop_t)(struct fastop *);
> +
> struct x86_emulate_ctxt {
> const struct x86_emulate_ops *ops;
>
> @@ -324,7 +332,10 @@ struct x86_emulate_ctxt {
> struct operand src;
> struct operand src2;
> struct operand dst;
> - int (*execute)(struct x86_emulate_ctxt *ctxt);
> + union {
> + int (*execute)(struct x86_emulate_ctxt *ctxt);
> + fastop_t fop;
> + };
> int (*check_perm)(struct x86_emulate_ctxt *ctxt);
> /*
> * The following six fields are cleared together,
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index ddbc61984227..dd19fb3539e0 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -191,25 +191,6 @@
> #define NR_FASTOP (ilog2(sizeof(ulong)) + 1)
> #define FASTOP_SIZE 8
>
> -/*
> - * fastop functions have a special calling convention:
> - *
> - * dst: rax (in/out)
> - * src: rdx (in/out)
> - * src2: rcx (in)
> - * flags: rflags (in/out)
> - * ex: rsi (in:fastop pointer, out:zero if exception)
> - *
> - * Moreover, they are all exactly FASTOP_SIZE bytes long, so functions for
> - * different operand sizes can be reached by calculation, rather than a jump
> - * table (which would be bigger than the code).
> - *
> - * fastop functions are declared as taking a never-defined fastop parameter,
> - * so they can't be called from C directly.
> - */
> -
> -struct fastop;
> -
> struct opcode {
> u64 flags : 56;
> u64 intercept : 8;
> @@ -311,8 +292,19 @@ static void invalidate_registers(struct x86_emulate_ctxt
> *ctxt)
> #define ON64(x)
> #endif
>
> -typedef void (*fastop_t)(struct fastop *);
> -
> +/*
> + * fastop functions have a special calling convention:
> + *
> + * dst: rax (in/out)
> + * src: rdx (in/out)
> + * src2: rcx (in)
> + * flags: rflags (in/out)
> + * ex: rsi (in:fastop pointer, out:zero if exception)
> + *
> + * Moreover, they are all exactly FASTOP_SIZE bytes long, so functions for
> + * different operand sizes can be reached by calculation, rather than a jump
> + * table (which would be bigger than the code).
> + */
> static int fastop(struct x86_emulate_ctxt *ctxt, fastop_t fop);
>
> #define __FOP_FUNC(name) \
> @@ -5683,7 +5675,7 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
>
> if (ctxt->execute) {
> if (ctxt->d & Fastop)
> - rc = fastop(ctxt, (fastop_t)ctxt->execute);
> + rc = fastop(ctxt, ctxt->fop);
> else
> rc = ctxt->execute(ctxt);
> if (rc != X86EMUL_CONTINUE)
>