[xen master] xen/x86: account for assigned PCI devices in cache_flush_permitted()

[patchbot@xxxxxxx]

commit 8333e358e4cda629ed46398dc3ea4510d3d48d70
Author:     Roger Pau Monne <roger.pau@xxxxxxxxxx>
AuthorDate: Fri May 16 10:56:51 2025 +0200
Commit:     Roger Pau Monne <roger.pau@xxxxxxxxxx>
CommitDate: Tue May 20 16:35:52 2025 +0200

    xen/x86: account for assigned PCI devices in cache_flush_permitted()
    
    While unlikely, it's possible for PCI devices to not have any IO resources
    assigned, yet in such case the owner domain might still need to issue cache
    control operations in case the device performs DMA requests.
    
    Adjust cache_flush_permitted() to account for has_arch_pdevs().
    
    While there also switch l1_disallow_mask() to use cache_flush_permitted().
    This should be a non-functional change after the adjustment done to
    cache_flush_permitted().
    
    Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/include/asm/iocap.h | 3 ++-
 xen/arch/x86/mm.c                | 4 +---
 2 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/include/asm/iocap.h b/xen/arch/x86/include/asm/iocap.h
index 61d026dbf5..f948b7186e 100644
--- a/xen/arch/x86/include/asm/iocap.h
+++ b/xen/arch/x86/include/asm/iocap.h
@@ -19,7 +19,8 @@
     (!rangeset_is_empty((d)->iomem_caps) ||             \
      !rangeset_is_empty((d)->arch.ioport_caps))
 
-#define cache_flush_permitted has_arch_io_resources
+#define cache_flush_permitted(d) \
+    (has_arch_io_resources(d) || has_arch_pdevs(d))
 
 static inline int ioports_permit_access(struct domain *d, unsigned long s,
                                         unsigned long e)
diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index a1703db762..657623336c 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -172,9 +172,7 @@ static DEFINE_SPINLOCK(subpage_ro_lock);
 
 #define l1_disallow_mask(d)                                     \
     (((d) != dom_io) &&                                         \
-     (rangeset_is_empty((d)->iomem_caps) &&                     \
-      rangeset_is_empty((d)->arch.ioport_caps) &&               \
-      !has_arch_pdevs(d) &&                                     \
+     (!cache_flush_permitted(d) &&                              \
       is_pv_domain(d)) ?                                        \
      L1_DISALLOW_MASK : (L1_DISALLOW_MASK & ~PAGE_CACHE_ATTRS))
 
--
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