Re: [RFC PATCH 08/21] xen/arm: vsmmuv3: Add support for registers emulation

[Julien Grall <julien@xxxxxxx>]

Hi Rahul,

I have only skimmed through the patch so far.

On 01/12/2022 16:02, Rahul Singh wrote:
>   static int vsmmuv3_mmio_write(struct vcpu *v, mmio_info_t *info,
>                                 register_t r, void *priv)
>   {
> +    struct virt_smmu *smmu = priv;
> +    uint64_t reg;
> +    uint32_t reg32;
> +
> +    switch ( info->gpa & 0xffff )
> +    {
> +    case VREG32(ARM_SMMU_CR0):

Shouldn't this code (and all the other register emulations) be protected 
for concurrent access in some way?

> +        reg32 = smmu->cr[0];
> +        vreg_reg32_update(&reg32, r, info);
> +        smmu->cr[0] = reg32;
> +        smmu->cr0ack = reg32 & ~CR0_RESERVED;
Looking at the use. I think it doesn't look necessary to have a copy of 
cr0 with just the reserved bit(s) unset. Instead, it would be better to 
clear the bit(s) when reading it.
Cheers,

--
Julien Grall