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

[Julien Grall]

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