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Subject[PATCH 8/9] x86/xen: do not use _PAGE_IOMAP PTE flag for I/O mappings
Date
Since mfn_to_pfn() returns the correct PFN for identity mappings (as
used for MMIO regions), the use of _PAGE_IOMAP is not required in
pte_mfn_to_pfn().

Do not set the _PAGE_IOMAP flag in pte_pfn_to_mfn() and do not use it
in pte_mfn_to_pfn().

This will allow _PAGE_IOMAP to be removed, making it available for
future use.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
---
arch/x86/xen/mmu.c | 48 ++++--------------------------------------------
1 files changed, 4 insertions(+), 44 deletions(-)

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index d916024..b86ebff 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -399,38 +399,14 @@ static pteval_t pte_pfn_to_mfn(pteval_t val)
if (unlikely(mfn == INVALID_P2M_ENTRY)) {
mfn = 0;
flags = 0;
- } else {
- /*
- * Paramount to do this test _after_ the
- * INVALID_P2M_ENTRY as INVALID_P2M_ENTRY &
- * IDENTITY_FRAME_BIT resolves to true.
- */
- mfn &= ~FOREIGN_FRAME_BIT;
- if (mfn & IDENTITY_FRAME_BIT) {
- mfn &= ~IDENTITY_FRAME_BIT;
- flags |= _PAGE_IOMAP;
- }
- }
+ } else
+ mfn &= ~(FOREIGN_FRAME_BIT | IDENTITY_FRAME_BIT);
val = ((pteval_t)mfn << PAGE_SHIFT) | flags;
}

return val;
}

-static pteval_t iomap_pte(pteval_t val)
-{
- if (val & _PAGE_PRESENT) {
- unsigned long pfn = (val & PTE_PFN_MASK) >> PAGE_SHIFT;
- pteval_t flags = val & PTE_FLAGS_MASK;
-
- /* We assume the pte frame number is a MFN, so
- just use it as-is. */
- val = ((pteval_t)pfn << PAGE_SHIFT) | flags;
- }
-
- return val;
-}
-
__visible pteval_t xen_pte_val(pte_t pte)
{
pteval_t pteval = pte.pte;
@@ -441,9 +417,6 @@ __visible pteval_t xen_pte_val(pte_t pte)
pteval = (pteval & ~_PAGE_PAT) | _PAGE_PWT;
}
#endif
- if (xen_initial_domain() && (pteval & _PAGE_IOMAP))
- return pteval;
-
return pte_mfn_to_pfn(pteval);
}
PV_CALLEE_SAVE_REGS_THUNK(xen_pte_val);
@@ -481,7 +454,6 @@ void xen_set_pat(u64 pat)

__visible pte_t xen_make_pte(pteval_t pte)
{
- phys_addr_t addr = (pte & PTE_PFN_MASK);
#if 0
/* If Linux is trying to set a WC pte, then map to the Xen WC.
* If _PAGE_PAT is set, then it probably means it is really
@@ -496,19 +468,7 @@ __visible pte_t xen_make_pte(pteval_t pte)
pte = (pte & ~(_PAGE_PCD | _PAGE_PWT)) | _PAGE_PAT;
}
#endif
- /*
- * Unprivileged domains are allowed to do IOMAPpings for
- * PCI passthrough, but not map ISA space. The ISA
- * mappings are just dummy local mappings to keep other
- * parts of the kernel happy.
- */
- if (unlikely(pte & _PAGE_IOMAP) &&
- (xen_initial_domain() || addr >= ISA_END_ADDRESS)) {
- pte = iomap_pte(pte);
- } else {
- pte &= ~_PAGE_IOMAP;
- pte = pte_pfn_to_mfn(pte);
- }
+ pte = pte_pfn_to_mfn(pte);

return native_make_pte(pte);
}
@@ -2095,7 +2055,7 @@ static void xen_set_fixmap(unsigned idx, phys_addr_t phys, pgprot_t prot)

default:
/* By default, set_fixmap is used for hardware mappings */
- pte = mfn_pte(phys, __pgprot(pgprot_val(prot) | _PAGE_IOMAP));
+ pte = mfn_pte(phys, prot);
break;
}

--
1.7.2.5


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