On 28/11/12 13:09, Will Deacon wrote:
> On Sat, Nov 10, 2012 at 03:44:44PM +0000, Christoffer Dall wrote:
>> From: Marc Zyngier <[email protected]>
>>
>> Wire the initial in-kernel MMIO support code for the VGIC, used
>> for the distributor emulation.
>
> [...]
>
>> diff --git a/arch/arm/kvm/vgic.c b/arch/arm/kvm/vgic.c
>> new file mode 100644
>> index 0000000..26ada3b
>> --- /dev/null
>> +++ b/arch/arm/kvm/vgic.c
>> @@ -0,0 +1,138 @@
>> +/*
>> + * Copyright (C) 2012 ARM Ltd.
>> + * Author: Marc Zyngier <[email protected]>
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License version 2 as
>> + * published by the Free Software Foundation.
>> + *
>> + * This program is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
>> + * GNU General Public License for more details.
>> + *
>> + * You should have received a copy of the GNU General Public License
>> + * along with this program; if not, write to the Free Software
>> + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
>> + */
>> +
>> +#include <linux/kvm.h>
>> +#include <linux/kvm_host.h>
>> +#include <linux/interrupt.h>
>> +#include <linux/io.h>
>> +#include <asm/kvm_emulate.h>
>> +
>> +#define ACCESS_READ_VALUE (1 << 0)
>> +#define ACCESS_READ_RAZ (0 << 0)
>> +#define ACCESS_READ_MASK(x) ((x) & (1 << 0))
>> +#define ACCESS_WRITE_IGNORED (0 << 1)
>> +#define ACCESS_WRITE_SETBIT (1 << 1)
>> +#define ACCESS_WRITE_CLEARBIT (2 << 1)
>> +#define ACCESS_WRITE_VALUE (3 << 1)
>> +#define ACCESS_WRITE_MASK(x) ((x) & (3 << 1))
>> +
>> +/**
>> + * vgic_reg_access - access vgic register
>> + * @mmio: pointer to the data describing the mmio access
>> + * @reg: pointer to the virtual backing of the vgic distributor struct
>> + * @offset: least significant 2 bits used for word offset
>> + * @mode: ACCESS_ mode (see defines above)
>> + *
>> + * Helper to make vgic register access easier using one of the access
>> + * modes defined for vgic register access
>> + * (read,raz,write-ignored,setbit,clearbit,write)
>> + */
>> +static void vgic_reg_access(struct kvm_exit_mmio *mmio, u32 *reg,
>> + u32 offset, int mode)
>> +{
>> + int word_offset = offset & 3;
>
> You can get rid of this variable.
>
>> + int shift = word_offset * 8;
>
> shift = (offset & 3) << 3;
>
>> + u32 mask;
>> + u32 regval;
>> +
>> + /*
>> + * Any alignment fault should have been delivered to the guest
>> + * directly (ARM ARM B3.12.7 "Prioritization of aborts").
>> + */
>> +
>> + mask = (~0U) >> (word_offset * 8);
>
> then use shift here.
Sure.
>> + if (reg)
>> + regval = *reg;
>> + else {
>
> Use braces for the if clause.
Indeed.
>
>> + BUG_ON(mode != (ACCESS_READ_RAZ | ACCESS_WRITE_IGNORED));
>> + regval = 0;
>> + }
>> +
>> + if (mmio->is_write) {
>> + u32 data = (*((u32 *)mmio->data) & mask) << shift;
>> + switch (ACCESS_WRITE_MASK(mode)) {
>> + case ACCESS_WRITE_IGNORED:
>> + return;
>> +
>> + case ACCESS_WRITE_SETBIT:
>> + regval |= data;
>> + break;
>> +
>> + case ACCESS_WRITE_CLEARBIT:
>> + regval &= ~data;
>> + break;
>> +
>> + case ACCESS_WRITE_VALUE:
>> + regval = (regval & ~(mask << shift)) | data;
>> + break;
>> + }
>> + *reg = regval;
>> + } else {
>> + switch (ACCESS_READ_MASK(mode)) {
>> + case ACCESS_READ_RAZ:
>> + regval = 0;
>> + /* fall through */
>> +
>> + case ACCESS_READ_VALUE:
>> + *((u32 *)mmio->data) = (regval >> shift) & mask;
>> + }
>> + }
>> +}
>
> It might be a good idea to have some port accessors for mmio->data otherwise
> you'll likely get endianness issues creeping in.
Aarrgh! This depends on the relative endianess of host and guest. 'm
feeling slightly sick...
>> +/* All this should be handled by kvm_bus_io_*()... FIXME!!! */
>
> I don't follow this comment :) Can you either make it clearer (and less
> alarming!) or just drop it please?
The non-alarming version should read:
/*
* I would have liked to use the kvm_bus_io_*() API instead, but
* it cannot cope with banked registers (only the VM pointer is
* passed around, and we need the vcpu). One of these days, someone
* please fix it!
*/
>
>> +struct mmio_range {
>> + unsigned long base;
>> + unsigned long len;
>> + bool (*handle_mmio)(struct kvm_vcpu *vcpu, struct kvm_exit_mmio *mmio,
>> + u32 offset);
>> +};
>
> Why not make offset a phys_addr_t?
Very good point.
>> +static const struct mmio_range vgic_ranges[] = {
>> + {}
>> +};
>> +
>> +static const
>> +struct mmio_range *find_matching_range(const struct mmio_range *ranges,
>> + struct kvm_exit_mmio *mmio,
>> + unsigned long base)
>> +{
>> + const struct mmio_range *r = ranges;
>> + unsigned long addr = mmio->phys_addr - base;
>
> Same here, I don't think we want to truncate everything to unsigned long.
Indeed.
>> + while (r->len) {
>> + if (addr >= r->base &&
>> + (addr + mmio->len) <= (r->base + r->len))
>> + return r;
>> + r++;
>> + }
>
> Hmm, does this work correctly for adjacent mmio devices where addr sits
> on the boundary (i.e. the first address of the second device)?
I think it is OK. We basically check that both ends of the access are
within a single range (we do not bother with cross range accesses).
M.
--
Jazz is not dead. It just smells funny...
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