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Re: [PATCH v3 2/2] xen/arm: vpl011: drop redundancy in mmio_write/read
Hi,
On 29/11/2022 03:39, Jiamei Xie wrote:
This commit is to drop redundancy in the function vpl011_mmio_write
and vpl011_mmio_read:
- In vpl011_mmio_read switch block, all cases have a return. So the
outside one can be removed.
- Each switch case checks access by the same if statments. So we can
just use one and put it before the switch block.
- The goto label bad_width and read_as_zero is used only once, put the
code directly
Signed-off-by: Jiamei Xie <jiamei.xie@xxxxxxx>
---
xen/arch/arm/vpl011.c | 66 +++++++++++++------------------------------
1 file changed, 19 insertions(+), 47 deletions(-)
diff --git a/xen/arch/arm/vpl011.c b/xen/arch/arm/vpl011.c
index 1bf803fc1f..80b859baed 100644
--- a/xen/arch/arm/vpl011.c
+++ b/xen/arch/arm/vpl011.c
@@ -354,11 +354,15 @@ static int vpl011_mmio_read(struct vcpu *v,
struct domain *d = v->domain;
unsigned long flags;
+ if ( !vpl011_reg32_check_access(dabt) ) {
As I pointed out in the previous version, we don't know the size of the
registers for the one not described in the SBSA UART. So I don't think
this check should be consolidated.
Also, coding style:
if ( .... )
{
+ gprintk(XENLOG_ERR, "vpl011: bad read width %d r%d offset %#08x\n",
+ dabt.size, dabt.reg, vpl011_reg);
+ return 0;
+ }
+
switch ( vpl011_reg )
{
case DR:
- if ( !vpl011_reg32_check_access(dabt) ) goto bad_width;
-
if ( vpl011->backend_in_domain )
*r = vreg_reg32_extract(vpl011_read_data(d), info);
else
@@ -366,31 +370,23 @@ static int vpl011_mmio_read(struct vcpu *v,
return 1;
case RSR:
- if ( !vpl011_reg32_check_access(dabt) ) goto bad_width;
-
/* It always returns 0 as there are no physical errors. */
*r = 0;
return 1;
case FR:
- if ( !vpl011_reg32_check_access(dabt) ) goto bad_width;
-
VPL011_LOCK(d, flags);
*r = vreg_reg32_extract(vpl011->uartfr, info);
VPL011_UNLOCK(d, flags);
return 1;
case RIS:
- if ( !vpl011_reg32_check_access(dabt) ) goto bad_width;
-
VPL011_LOCK(d, flags);
*r = vreg_reg32_extract(vpl011->uartris, info);
VPL011_UNLOCK(d, flags);
return 1;
case MIS:
- if ( !vpl011_reg32_check_access(dabt) ) goto bad_width;
-
VPL011_LOCK(d, flags);
*r = vreg_reg32_extract(vpl011->uartris & vpl011->uartimsc,
info);
@@ -398,40 +394,25 @@ static int vpl011_mmio_read(struct vcpu *v,
return 1;
case IMSC:
- if ( !vpl011_reg32_check_access(dabt) ) goto bad_width;
-
VPL011_LOCK(d, flags);
*r = vreg_reg32_extract(vpl011->uartimsc, info);
VPL011_UNLOCK(d, flags);
return 1;
case ICR:
- if ( !vpl011_reg32_check_access(dabt) ) goto bad_width;
-
/* Only write is valid. */
return 0;
default:
gprintk(XENLOG_ERR, "vpl011: unhandled read r%d offset %#08x\n",
dabt.reg, vpl011_reg);
- goto read_as_zero;
- }
-
- return 1;
-
-read_as_zero:
In general, we don't want to introduce and remove the same code within a
series. If you don't want to keep read_as_zero, then you should not
introduce it.
However... I think using the read_as_zero label could still be
beneficial to reduce the numbers of lines where the registers are RAZ
(e.g. default, RSR...).
- if ( !vpl011_reg32_check_access(dabt) ) goto bad_width;
-
- VPL011_LOCK(d, flags);
- *r = 0;
- VPL011_UNLOCK(d, flags);
- return 1;
-
-bad_width:
- gprintk(XENLOG_ERR, "vpl011: bad read width %d r%d offset %#08x\n",
- dabt.size, dabt.reg, vpl011_reg);
- return 0;
+ /* Read as zero */
+ VPL011_LOCK(d, flags);
+ *r = 0;
+ VPL011_UNLOCK(d, flags);
+ return 1;
+ }
}
static int vpl011_mmio_write(struct vcpu *v,
@@ -446,14 +427,18 @@ static int vpl011_mmio_write(struct vcpu *v,
struct domain *d = v->domain;
unsigned long flags;
- switch ( vpl011_reg )
+ if ( !vpl011_reg32_check_access(dabt) ) {
+ gprintk(XENLOG_ERR, "vpl011: bad write width %d r%d offset %#08x\n",
+ dabt.size, dabt.reg, vpl011_reg);
+ return 0;
+ }
Same remarks as for the read part.
+
+ switch ( vpl011_reg )
{
case DR:
{
uint32_t data = 0;
- if ( !vpl011_reg32_check_access(dabt) ) goto bad_width;
-
vreg_reg32_update(&data, r, info);
data &= 0xFF;
if ( vpl011->backend_in_domain )
@@ -464,8 +449,6 @@ static int vpl011_mmio_write(struct vcpu *v,
}
case RSR: /* Nothing to clear. */
- if ( !vpl011_reg32_check_access(dabt) ) goto bad_width;
-
return 1;
case FR:
@@ -474,8 +457,6 @@ static int vpl011_mmio_write(struct vcpu *v,
goto write_ignore;
case IMSC:
- if ( !vpl011_reg32_check_access(dabt) ) goto bad_width;
-
VPL011_LOCK(d, flags);
vreg_reg32_update(&vpl011->uartimsc, r, info);
vpl011_update_interrupt_status(v->domain);
@@ -483,8 +464,6 @@ static int vpl011_mmio_write(struct vcpu *v,
return 1;
case ICR:
- if ( !vpl011_reg32_check_access(dabt) ) goto bad_width;
-
VPL011_LOCK(d, flags);
vreg_reg32_clearbits(&vpl011->uartris, r, info);
vpl011_update_interrupt_status(d);
@@ -498,14 +477,7 @@ static int vpl011_mmio_write(struct vcpu *v,
}
write_ignore:
- if ( !vpl011_reg32_check_access(dabt) ) goto bad_width;
return 1;
-
-bad_width:
- gprintk(XENLOG_ERR, "vpl011: bad write width %d r%d offset %#08x\n",
- dabt.size, dabt.reg, vpl011_reg);
- return 0;
-
}
static const struct mmio_handler_ops vpl011_mmio_handler = {
--
Julien Grall
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