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xen: add support for PAT
Convert Linux PAT entries into Xen ones when constructing ptes. Linux doesn't use _PAGE_PAT for ptes, so the only difference in the first 4 entries is that Linux uses _PAGE_PWT for WC, whereas Xen (and default) use it for WT. xen_pte_val does the inverse conversion. We hard-code assumptions about Linux's current PAT layout, but a warning on the wrmsr to MSR_IA32_CR_PAT should point out any problems. If necessary we could go to a more general table-based conversion between Linux and Xen PAT entries. hugetlbfs poses a problem at the moment, the x86 architecture uses the same flag for _PAGE_PAT and _PAGE_PSE, which changes meaning depending on which pagetable level we're using. At the moment this should be OK so long as nobody tries to do a pte_val on a hugetlbfs pte. Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
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2f7acb2085
commit
41f2e4771a
3 changed files with 57 additions and 3 deletions
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@ -829,6 +829,11 @@ static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high)
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Xen console noise. */
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break;
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case MSR_IA32_CR_PAT:
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if (smp_processor_id() == 0)
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xen_set_pat(((u64)high << 32) | low);
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break;
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default:
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ret = native_write_msr_safe(msr, low, high);
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}
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@ -55,6 +55,7 @@
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#include <asm/e820.h>
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#include <asm/linkage.h>
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#include <asm/page.h>
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#include <asm/pat.h>
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#include <asm/xen/hypercall.h>
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#include <asm/xen/hypervisor.h>
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@ -780,10 +781,18 @@ static pteval_t iomap_pte(pteval_t val)
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pteval_t xen_pte_val(pte_t pte)
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{
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if (xen_initial_domain() && (pte.pte & _PAGE_IOMAP))
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return pte.pte;
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pteval_t pteval = pte.pte;
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return pte_mfn_to_pfn(pte.pte);
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/* If this is a WC pte, convert back from Xen WC to Linux WC */
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if ((pteval & (_PAGE_PAT | _PAGE_PCD | _PAGE_PWT)) == _PAGE_PAT) {
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WARN_ON(!pat_enabled);
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pteval = (pteval & ~_PAGE_PAT) | _PAGE_PWT;
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}
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if (xen_initial_domain() && (pteval & _PAGE_IOMAP))
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return pteval;
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return pte_mfn_to_pfn(pteval);
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}
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PV_CALLEE_SAVE_REGS_THUNK(xen_pte_val);
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@ -793,10 +802,48 @@ pgdval_t xen_pgd_val(pgd_t pgd)
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}
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PV_CALLEE_SAVE_REGS_THUNK(xen_pgd_val);
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/*
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* Xen's PAT setup is part of its ABI, though I assume entries 6 & 7
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* are reserved for now, to correspond to the Intel-reserved PAT
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* types.
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*
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* We expect Linux's PAT set as follows:
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*
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* Idx PTE flags Linux Xen Default
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* 0 WB WB WB
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* 1 PWT WC WT WT
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* 2 PCD UC- UC- UC-
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* 3 PCD PWT UC UC UC
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* 4 PAT WB WC WB
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* 5 PAT PWT WC WP WT
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* 6 PAT PCD UC- UC UC-
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* 7 PAT PCD PWT UC UC UC
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*/
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void xen_set_pat(u64 pat)
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{
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/* We expect Linux to use a PAT setting of
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* UC UC- WC WB (ignoring the PAT flag) */
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WARN_ON(pat != 0x0007010600070106ull);
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}
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pte_t xen_make_pte(pteval_t pte)
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{
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phys_addr_t addr = (pte & PTE_PFN_MASK);
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/* If Linux is trying to set a WC pte, then map to the Xen WC.
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* If _PAGE_PAT is set, then it probably means it is really
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* _PAGE_PSE, so avoid fiddling with the PAT mapping and hope
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* things work out OK...
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*
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* (We should never see kernel mappings with _PAGE_PSE set,
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* but we could see hugetlbfs mappings, I think.).
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*/
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if (pat_enabled && !WARN_ON(pte & _PAGE_PAT)) {
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if ((pte & (_PAGE_PCD | _PAGE_PWT)) == _PAGE_PWT)
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pte = (pte & ~(_PAGE_PCD | _PAGE_PWT)) | _PAGE_PAT;
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}
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/*
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* Unprivileged domains are allowed to do IOMAPpings for
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* PCI passthrough, but not map ISA space. The ISA
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@ -32,6 +32,8 @@ void xen_ident_map_ISA(void);
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void xen_reserve_top(void);
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extern unsigned long xen_max_p2m_pfn;
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void xen_set_pat(u64);
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char * __init xen_memory_setup(void);
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void __init xen_arch_setup(void);
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void __init xen_init_IRQ(void);
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