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Re: [RFC PATCH 08/21] xen/arm: vsmmuv3: Add support for registers emulation
- To: Julien Grall <julien@xxxxxxx>
- From: Rahul Singh <Rahul.Singh@xxxxxxx>
- Date: Mon, 5 Dec 2022 14:56:57 +0000
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- Cc: Xen developer discussion <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Bertrand Marquis <Bertrand.Marquis@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
- Delivery-date: Mon, 05 Dec 2022 14:57:14 +0000
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- Thread-topic: [RFC PATCH 08/21] xen/arm: vsmmuv3: Add support for registers emulation
Hi Julien,
> On 3 Dec 2022, at 9:16 pm, Julien Grall <julien@xxxxxxx> wrote:
>
> 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?
Yes, I agree I will add the lock for register emulations in next v2.
>
>
>> + reg32 = smmu->cr[0];
>> + vreg_reg32_update(®32, 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.
Ack.
Regards,
Rahul
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