[xen staging] x86/EPT: drop questionable mfn_valid() from epte_get_entry_emt()

[patchbot@xxxxxxx]

commit 4fdd8d75566fdad06667a79ec0ce6f43cc466c54
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Thu Jun 13 16:55:22 2024 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Jun 13 16:55:22 2024 +0200

    x86/EPT: drop questionable mfn_valid() from epte_get_entry_emt()
    
    mfn_valid() is RAM-focused; it will often return false for MMIO. Yet
    access to actual MMIO space should not generally be restricted to UC
    only; especially video frame buffer accesses are unduly affected by such
    a restriction.
    
    Since, as of 777c71d31325 ("x86/EPT: avoid marking non-present entries
    for re-configuring"), the function won't be called with INVALID_MFN or,
    worse, truncated forms thereof anymore, we call fully drop that check.
    
    Fixes: 81fd0d3ca4b2 ("x86/hvm: simplify 'mmio_direct' check in 
epte_get_entry_emt()")
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Release-Acked-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
---
 xen/arch/x86/mm/p2m-ept.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c
index a3ffb97876..469e27ee93 100644
--- a/xen/arch/x86/mm/p2m-ept.c
+++ b/xen/arch/x86/mm/p2m-ept.c
@@ -501,12 +501,6 @@ int epte_get_entry_emt(struct domain *d, gfn_t gfn, mfn_t 
mfn,
         return -1;
     }
 
-    if ( !mfn_valid(mfn) )
-    {
-        *ipat = true;
-        return X86_MT_UC;
-    }
-
     /*
      * Conditional must be kept in sync with the code in
      * {iomem,ioports}_{permit,deny}_access().
--
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