Re: [PATCH v3 2/5] xen/common: Guard iommu symbols with CONFIG_HAS_PASSTHROUGH

[Connor Davis]

On 5/17/21 5:16 AM, Jan Beulich wrote:

On 14.05.2021 20:53, Connor Davis wrote:

--- a/xen/common/memory.c
+++ b/xen/common/memory.c
@@ -294,7 +294,9 @@ int guest_remove_page(struct domain *d, unsigned long gmfn)
      p2m_type_t p2mt;
  #endif
      mfn_t mfn;
+#ifdef CONFIG_HAS_PASSTHROUGH
      bool *dont_flush_p, dont_flush;
+#endif
      int rc;

#ifdef CONFIG_X86

@@ -385,13 +387,17 @@ int guest_remove_page(struct domain *d, unsigned long 
gmfn)
       * Since we're likely to free the page below, we need to suspend
       * xenmem_add_to_physmap()'s suppressing of IOMMU TLB flushes.
       */
+#ifdef CONFIG_HAS_PASSTHROUGH
      dont_flush_p = &this_cpu(iommu_dont_flush_iotlb);
      dont_flush = *dont_flush_p;
      *dont_flush_p = false;
+#endif

rc = guest_physmap_remove_page(d, _gfn(gmfn), mfn, 0); +#ifdef CONFIG_HAS_PASSTHROUGH

      *dont_flush_p = dont_flush;
+#endif

/*

       * With the lack of an IOMMU on some platforms, domains with DMA-capable
@@ -839,11 +845,13 @@ int xenmem_add_to_physmap(struct domain *d, struct 
xen_add_to_physmap *xatp,
      xatp->gpfn += start;
      xatp->size -= start;

+#ifdef CONFIG_HAS_PASSTHROUGH

      if ( is_iommu_enabled(d) )
      {
         this_cpu(iommu_dont_flush_iotlb) = 1;
         extra.ppage = &pages[0];
      }
+#endif

while ( xatp->size > done )

      {
@@ -868,6 +876,7 @@ int xenmem_add_to_physmap(struct domain *d, struct 
xen_add_to_physmap *xatp,
          }
      }

+#ifdef CONFIG_HAS_PASSTHROUGH

      if ( is_iommu_enabled(d) )
      {
          int ret;
@@ -894,6 +903,7 @@ int xenmem_add_to_physmap(struct domain *d, struct 
xen_add_to_physmap *xatp,
          if ( unlikely(ret) && rc >= 0 )
              rc = ret;
      }
+#endif

return rc;

  }

I wonder whether all of these wouldn't better become CONFIG_X86:
ISTR Julien indicating that he doesn't see the override getting used
on Arm. (Julien, please correct me if I'm misremembering.)

--- a/xen/include/xen/iommu.h
+++ b/xen/include/xen/iommu.h
@@ -51,9 +51,15 @@ static inline bool_t dfn_eq(dfn_t x, dfn_t y)
      return dfn_x(x) == dfn_x(y);
  }

-extern bool_t iommu_enable, iommu_enabled;

+extern bool_t iommu_enable;
  extern bool force_iommu, iommu_quarantine, iommu_verbose;

+#ifdef CONFIG_HAS_PASSTHROUGH

+extern bool_t iommu_enabled;

Just bool please, like is already the case for the line in context
above. We're in the process of phasing out bool_t.

Got it, thanks.

Jan

Thanks,

Connor