Hi Christoffer,
On 15/10/14 17:26, Christoffer Dall wrote:
> On Thu, Aug 21, 2014 at 02:06:45PM +0100, Andre Przywara wrote:
>> Some GICv3 registers can and will be accessed as 64 bit registers.
>> Currently the register handling code can only deal with 32 bit
>> accesses, so we do two consecutive calls to cover this.
>>
>> Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
>> ---
>> virt/kvm/arm/vgic.c | 48 +++++++++++++++++++++++++++++++++++++++++++++---
>> 1 file changed, 45 insertions(+), 3 deletions(-)
>>
>> diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
>> index 3b6f78d..bef9aa0 100644
>> --- a/virt/kvm/arm/vgic.c
>> +++ b/virt/kvm/arm/vgic.c
>> @@ -926,6 +926,48 @@ static bool vgic_validate_access(const struct vgic_dist *dist,
>> }
>>
>> /*
>> + * Call the respective handler function for the given range.
>> + * We split up any 64 bit accesses into two consecutive 32 bit
>> + * handler calls and merge the result afterwards.
>> + */
>> +static bool call_range_handler(struct kvm_vcpu *vcpu,
>> + struct kvm_exit_mmio *mmio,
>> + unsigned long offset,
>> + const struct mmio_range *range)
>> +{
>> + u32 *data32 = (void *)mmio->data;
>> + struct kvm_exit_mmio mmio32;
>> + bool ret;
>> +
>> + if (likely(mmio->len <= 4))
>> + return range->handle_mmio(vcpu, mmio, offset);
>> +
>> + /*
>> + * We assume that any access greater than 4 bytes is actually
>
> Is this an assumption or something that will always hold true at this
> point in the code? If the former, which situations could it not hold
> and what would happen? If the latter, we should just state that.
I wasn't so sure about this at the time of writing ;-)
So I see how one can read/write 1, 2, 4, 8 bytes and multiples of 4 or 8
bytes with ldm/ldp. For the latter we don't have syndrome support, so I
take it we don't care about this.
So if nobody sees other supported operand sizes when doing MMIO, I will
rephrase the above comment to be more strict.
>
>> + * 8 bytes long, caused by a 64-bit access
>> + */
>> +
>> + mmio32.len = 4;
>> + mmio32.is_write = mmio->is_write;
>> +
>> + mmio32.phys_addr = mmio->phys_addr + 4;
>> + if (mmio->is_write)
>> + *(u32 *)mmio32.data = data32[1];
>> + ret = range->handle_mmio(vcpu, &mmio32, offset + 4);
>> + if (!mmio->is_write)
>> + data32[1] = *(u32 *)mmio32.data;
>> +
>> + mmio32.phys_addr = mmio->phys_addr;
>> + if (mmio->is_write)
>> + *(u32 *)mmio32.data = data32[0];
>> + ret |= range->handle_mmio(vcpu, &mmio32, offset);
>> + if (!mmio->is_write)
>> + data32[0] = *(u32 *)mmio32.data;
>
> won't this break on a BE system?
Mmh, I remember having this discussed with Marc before. But I see that
it looks suspicious. This whole endianess thing is even more confusing
since the GIC is always LE and the guest as well as KVM already do swapping.
So I rewrote the above function to avoid explicit endianess assumptions,
but am still struggling to get it tested successfully on a bi-endian setup.
As I don't want to hold back the newer patches any longer, I will try to
debug this next week, meanwhile not stating bi-endianness is supported
for the new series.
Cheers,
Andre.
>
>> +
>> + return ret;
>> +}
>> +
>> +/*
>> * vgic_handle_mmio_range - handle an in-kernel MMIO access
>> * @vcpu: pointer to the vcpu performing the access
>> * @run: pointer to the kvm_run structure
>> @@ -956,10 +998,10 @@ static bool vgic_handle_mmio_range(struct kvm_vcpu *vcpu, struct kvm_run *run,
>> spin_lock(&vcpu->kvm->arch.vgic.lock);
>> offset -= range->base;
>> if (vgic_validate_access(dist, range, offset)) {
>> - updated_state = range->handle_mmio(vcpu, mmio, offset);
>> + updated_state = call_range_handler(vcpu, mmio, offset, range);
>> } else {
>> - vgic_reg_access(mmio, NULL, offset,
>> - ACCESS_READ_RAZ | ACCESS_WRITE_IGNORED);
>> + if (!mmio->is_write)
>> + memset(mmio->data, 0, mmio->len);
>> updated_state = false;
>> }
>> spin_unlock(&vcpu->kvm->arch.vgic.lock);
>> --
>> 1.7.9.5
>>
>
> Thanks,
> -Christoffer
>
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