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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 2/2] x86/xen: make mfn_to_pfn() work with MFNs that are 1:1 in the p2m
On Fri, Jan 03, 2014 at 04:45:22PM +0000, David Vrabel wrote:
> From: David Vrabel <david.vrabel@xxxxxxxxxx>
>
> The _PAGE_IOMAP PTE flag is used to indicate that the PTE contains an
> MFN that is an identify frame (1:1) in the p2m. This is so the
> correct conversion of MFN to PFN can be done reading a PTE.
>
> If mfn_to_pfn() returned the correct PFN instead the _PAGE_IOMAP flag
> is not required and can be removed.
>
> In mfn_to_pfn() the PFN found in the M2P is checked in P2M. If the
> two MFNs differ then the MFN is one of three possibilities:
>
> a) its a foreign MFN with an m2p override.
>
> b) it's a foreign MFN with /no/ m2p override.
>
> c) it's a identity MFN.
>
> It is not permitted to call mfn_to_pfn() no a foreign MFN without an
> override was the resulting PFN will not incorrect. We can therefore
> assume case (c) and return PFN == MFN.
>
> [ This patch should probably be split into the Xen-specific parts and
> an x86 patch to remove _PAGE_IOMAP. ]
Yeah :-)
>
> Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
> ---
> arch/x86/include/asm/pgtable_types.h | 12 +++---
> arch/x86/include/asm/xen/page.h | 18 +++++++---
> arch/x86/mm/init_32.c | 2 +-
> arch/x86/mm/init_64.c | 2 +-
> arch/x86/pci/i386.c | 2 -
> arch/x86/xen/enlighten.c | 2 -
> arch/x86/xen/mmu.c | 58
> +++++-----------------------------
> 7 files changed, 28 insertions(+), 68 deletions(-)
>
> diff --git a/arch/x86/include/asm/pgtable_types.h
> b/arch/x86/include/asm/pgtable_types.h
> index 0ecac25..0b12657 100644
> --- a/arch/x86/include/asm/pgtable_types.h
> +++ b/arch/x86/include/asm/pgtable_types.h
> @@ -17,7 +17,7 @@
> #define _PAGE_BIT_PAT 7 /* on 4KB pages */
> #define _PAGE_BIT_GLOBAL 8 /* Global TLB entry PPro+ */
> #define _PAGE_BIT_UNUSED1 9 /* available for programmer */
> -#define _PAGE_BIT_IOMAP 10 /* flag used to indicate IO
> mapping */
> +#define _PAGE_BIT_UNUSED2 10 /* available for programmer */
> #define _PAGE_BIT_HIDDEN 11 /* hidden by kmemcheck */
> #define _PAGE_BIT_PAT_LARGE 12 /* On 2MB or 1GB pages */
> #define _PAGE_BIT_SPECIAL _PAGE_BIT_UNUSED1
> @@ -41,7 +41,7 @@
> #define _PAGE_PSE (_AT(pteval_t, 1) << _PAGE_BIT_PSE)
> #define _PAGE_GLOBAL (_AT(pteval_t, 1) << _PAGE_BIT_GLOBAL)
> #define _PAGE_UNUSED1 (_AT(pteval_t, 1) << _PAGE_BIT_UNUSED1)
> -#define _PAGE_IOMAP (_AT(pteval_t, 1) << _PAGE_BIT_IOMAP)
> +#define _PAGE_UNUSED2 (_AT(pteval_t, 1) << _PAGE_BIT_UNUSED2)
> #define _PAGE_PAT (_AT(pteval_t, 1) << _PAGE_BIT_PAT)
> #define _PAGE_PAT_LARGE (_AT(pteval_t, 1) << _PAGE_BIT_PAT_LARGE)
> #define _PAGE_SPECIAL (_AT(pteval_t, 1) << _PAGE_BIT_SPECIAL)
> @@ -163,10 +163,10 @@
> #define __PAGE_KERNEL_LARGE_NOCACHE (__PAGE_KERNEL | _PAGE_CACHE_UC |
> _PAGE_PSE)
> #define __PAGE_KERNEL_LARGE_EXEC (__PAGE_KERNEL_EXEC | _PAGE_PSE)
>
> -#define __PAGE_KERNEL_IO (__PAGE_KERNEL | _PAGE_IOMAP)
> -#define __PAGE_KERNEL_IO_NOCACHE (__PAGE_KERNEL_NOCACHE | _PAGE_IOMAP)
> -#define __PAGE_KERNEL_IO_UC_MINUS (__PAGE_KERNEL_UC_MINUS | _PAGE_IOMAP)
> -#define __PAGE_KERNEL_IO_WC (__PAGE_KERNEL_WC | _PAGE_IOMAP)
> +#define __PAGE_KERNEL_IO (__PAGE_KERNEL)
> +#define __PAGE_KERNEL_IO_NOCACHE (__PAGE_KERNEL_NOCACHE)
> +#define __PAGE_KERNEL_IO_UC_MINUS (__PAGE_KERNEL_UC_MINUS)
> +#define __PAGE_KERNEL_IO_WC (__PAGE_KERNEL_WC)
>
> #define PAGE_KERNEL __pgprot(__PAGE_KERNEL)
> #define PAGE_KERNEL_RO __pgprot(__PAGE_KERNEL_RO)
> diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
> index b913915..eb11963 100644
> --- a/arch/x86/include/asm/xen/page.h
> +++ b/arch/x86/include/asm/xen/page.h
> @@ -112,11 +112,18 @@ static inline unsigned long mfn_to_pfn(unsigned long
> mfn)
> pfn = mfn_to_pfn_no_overrides(mfn);
> if (get_phys_to_machine(pfn) != mfn) {
> /*
> - * If this appears to be a foreign mfn (because the pfn
> - * doesn't map back to the mfn), then check the local override
> - * table to see if there's a better pfn to use.
> + * This is either:
> *
> - * m2p_find_override_pfn returns ~0 if it doesn't find anything.
> + * a) a foreign MFN with an override.
> + *
> + * b) a foreign MFN without an override.
> + *
> + * c) an identity MFN that is not in the the p2m.
> + *
> + * For (a), look in the m2p overrides. For (b) and
> + * (c) assume identify MFN since mfn_to_pfn() will
> + * only be called on foreign MFNs iff they have
> + * overrides.
> */
> pfn = m2p_find_override_pfn(mfn, ~0);
> }
> @@ -126,8 +133,7 @@ static inline unsigned long mfn_to_pfn(unsigned long mfn)
> * entry doesn't map back to the mfn and m2p_override doesn't have a
> * valid entry for it.
> */
> - if (pfn == ~0 &&
> - get_phys_to_machine(mfn) == IDENTITY_FRAME(mfn))
> + if (pfn == ~0)
> pfn = mfn;
>
> return pfn;
> diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
> index 4287f1f..9031593 100644
> --- a/arch/x86/mm/init_32.c
> +++ b/arch/x86/mm/init_32.c
> @@ -537,7 +537,7 @@ static void __init pagetable_init(void)
> permanent_kmaps_init(pgd_base);
> }
>
> -pteval_t __supported_pte_mask __read_mostly = ~(_PAGE_NX | _PAGE_GLOBAL |
> _PAGE_IOMAP);
> +pteval_t __supported_pte_mask __read_mostly = ~(_PAGE_NX | _PAGE_GLOBAL);
> EXPORT_SYMBOL_GPL(__supported_pte_mask);
>
> /* user-defined highmem size */
> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
> index 104d56a..68bf948 100644
> --- a/arch/x86/mm/init_64.c
> +++ b/arch/x86/mm/init_64.c
> @@ -151,7 +151,7 @@ early_param("gbpages", parse_direct_gbpages_on);
> * around without checking the pgd every time.
> */
>
> -pteval_t __supported_pte_mask __read_mostly = ~_PAGE_IOMAP;
> +pteval_t __supported_pte_mask __read_mostly = ~0;
> EXPORT_SYMBOL_GPL(__supported_pte_mask);
>
> int force_personality32;
> diff --git a/arch/x86/pci/i386.c b/arch/x86/pci/i386.c
> index db6b1ab..1f642d6 100644
> --- a/arch/x86/pci/i386.c
> +++ b/arch/x86/pci/i386.c
> @@ -433,8 +433,6 @@ int pci_mmap_page_range(struct pci_dev *dev, struct
> vm_area_struct *vma,
> */
> prot |= _PAGE_CACHE_UC_MINUS;
>
> - prot |= _PAGE_IOMAP; /* creating a mapping for IO */
> -
> vma->vm_page_prot = __pgprot(prot);
>
> if (io_remap_pfn_range(vma, vma->vm_start, vma->vm_pgoff,
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> index fa6ade7..f9c2d71 100644
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -1458,8 +1458,6 @@ asmlinkage void __init xen_start_kernel(void)
> #endif
> __supported_pte_mask &= ~(_PAGE_PWT | _PAGE_PCD);
>
> - __supported_pte_mask |= _PAGE_IOMAP;
> -
> /*
> * Prevent page tables from being allocated in highmem, even
> * if CONFIG_HIGHPTE is enabled.
> diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
> index ce563be..5fa77a1 100644
> --- a/arch/x86/xen/mmu.c
> +++ b/arch/x86/xen/mmu.c
> @@ -368,11 +368,9 @@ static pteval_t pte_mfn_to_pfn(pteval_t val)
> if (val & _PAGE_PRESENT) {
> unsigned long mfn = (val & PTE_PFN_MASK) >> PAGE_SHIFT;
> unsigned long pfn = mfn_to_pfn(mfn);
> -
> pteval_t flags = val & PTE_FLAGS_MASK;
> - if (unlikely(pfn == ~0))
> - val = flags & ~_PAGE_PRESENT;
> - else
> +
> + if (likely(pfn != ~0))
> val = ((pteval_t)pfn << PAGE_SHIFT) | flags;
> }
>
> @@ -390,6 +388,7 @@ static pteval_t pte_pfn_to_mfn(pteval_t val)
> mfn = get_phys_to_machine(pfn);
> else
> mfn = pfn;
> +
> /*
> * If there's no mfn for the pfn, then just create an
> * empty non-present pte. Unfortunately this loses
> @@ -399,38 +398,15 @@ 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;
> - }
> - }
> + mfn = pfn;
> + } 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;
> -}
> -
> static pteval_t xen_pte_val(pte_t pte)
> {
> pteval_t pteval = pte.pte;
> @@ -441,9 +417,6 @@ static 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)
>
> static 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 @@ static 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);
> }
> @@ -2084,7 +2044,7 @@ 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;
> }
>
> @@ -2524,8 +2484,6 @@ int xen_remap_domain_mfn_range(struct vm_area_struct
> *vma,
> if (xen_feature(XENFEAT_auto_translated_physmap))
> return -EINVAL;
>
> - prot = __pgprot(pgprot_val(prot) | _PAGE_IOMAP);
> -
> BUG_ON(!((vma->vm_flags & (VM_PFNMAP | VM_IO)) == (VM_PFNMAP | VM_IO)));
>
> rmd.mfn = mfn;
> --
> 1.7.2.5
>
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