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authorJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>2010-03-30 20:47:40 +0200
committerJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>2010-10-22 21:57:31 +0200
commit41f2e4771a4f1ba26c35438daf32917b9ef7858d (patch)
tree94a0af183907bc2f646bcde12072c960da987f65 /arch
parentxen: make sure xen_max_p2m_pfn is up to date (diff)
downloadlinux-41f2e4771a4f1ba26c35438daf32917b9ef7858d.tar.xz
linux-41f2e4771a4f1ba26c35438daf32917b9ef7858d.zip
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>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/xen/enlighten.c5
-rw-r--r--arch/x86/xen/mmu.c53
-rw-r--r--arch/x86/xen/xen-ops.h2
3 files changed, 57 insertions, 3 deletions
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index d8873014b5ed..b860e576ed0c 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -829,6 +829,11 @@ static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high)
Xen console noise. */
break;
+ case MSR_IA32_CR_PAT:
+ if (smp_processor_id() == 0)
+ xen_set_pat(((u64)high << 32) | low);
+ break;
+
default:
ret = native_write_msr_safe(msr, low, high);
}
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index b2371671b11c..67b41017f7b8 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -55,6 +55,7 @@
#include <asm/e820.h>
#include <asm/linkage.h>
#include <asm/page.h>
+#include <asm/pat.h>
#include <asm/xen/hypercall.h>
#include <asm/xen/hypervisor.h>
@@ -780,10 +781,18 @@ static pteval_t iomap_pte(pteval_t val)
pteval_t xen_pte_val(pte_t pte)
{
- if (xen_initial_domain() && (pte.pte & _PAGE_IOMAP))
- return pte.pte;
+ pteval_t pteval = pte.pte;
- return pte_mfn_to_pfn(pte.pte);
+ /* If this is a WC pte, convert back from Xen WC to Linux WC */
+ if ((pteval & (_PAGE_PAT | _PAGE_PCD | _PAGE_PWT)) == _PAGE_PAT) {
+ WARN_ON(!pat_enabled);
+ pteval = (pteval & ~_PAGE_PAT) | _PAGE_PWT;
+ }
+
+ if (xen_initial_domain() && (pteval & _PAGE_IOMAP))
+ return pteval;
+
+ return pte_mfn_to_pfn(pteval);
}
PV_CALLEE_SAVE_REGS_THUNK(xen_pte_val);
@@ -793,10 +802,48 @@ pgdval_t xen_pgd_val(pgd_t pgd)
}
PV_CALLEE_SAVE_REGS_THUNK(xen_pgd_val);
+/*
+ * Xen's PAT setup is part of its ABI, though I assume entries 6 & 7
+ * are reserved for now, to correspond to the Intel-reserved PAT
+ * types.
+ *
+ * We expect Linux's PAT set as follows:
+ *
+ * Idx PTE flags Linux Xen Default
+ * 0 WB WB WB
+ * 1 PWT WC WT WT
+ * 2 PCD UC- UC- UC-
+ * 3 PCD PWT UC UC UC
+ * 4 PAT WB WC WB
+ * 5 PAT PWT WC WP WT
+ * 6 PAT PCD UC- UC UC-
+ * 7 PAT PCD PWT UC UC UC
+ */
+
+void xen_set_pat(u64 pat)
+{
+ /* We expect Linux to use a PAT setting of
+ * UC UC- WC WB (ignoring the PAT flag) */
+ WARN_ON(pat != 0x0007010600070106ull);
+}
+
pte_t xen_make_pte(pteval_t pte)
{
phys_addr_t addr = (pte & PTE_PFN_MASK);
+ /* 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
+ * _PAGE_PSE, so avoid fiddling with the PAT mapping and hope
+ * things work out OK...
+ *
+ * (We should never see kernel mappings with _PAGE_PSE set,
+ * but we could see hugetlbfs mappings, I think.).
+ */
+ if (pat_enabled && !WARN_ON(pte & _PAGE_PAT)) {
+ if ((pte & (_PAGE_PCD | _PAGE_PWT)) == _PAGE_PWT)
+ pte = (pte & ~(_PAGE_PCD | _PAGE_PWT)) | _PAGE_PAT;
+ }
+
/*
* Unprivileged domains are allowed to do IOMAPpings for
* PCI passthrough, but not map ISA space. The ISA
diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
index d505e98e03f8..64044747348e 100644
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -32,6 +32,8 @@ void xen_ident_map_ISA(void);
void xen_reserve_top(void);
extern unsigned long xen_max_p2m_pfn;
+void xen_set_pat(u64);
+
char * __init xen_memory_setup(void);
void __init xen_arch_setup(void);
void __init xen_init_IRQ(void);