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Commit 7f2f8822 authored by David Vrabel's avatar David Vrabel Committed by Stefano Stabellini
Browse files

x86/xen: do not use _PAGE_IOMAP PTE flag for I/O mappings 



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: default avatarDavid Vrabel <david.vrabel@citrix.com>
Reviewed-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
parent 31668511

arch/x86/xen/mmu.c

+4 −44
Original line number Diff line number Diff line
@@ -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);

	}



	return native_make_pte(pte);

}
@@ -2091,7 +2051,7 @@ 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;

	}