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Message-Id: <1408454745-32358-4-git-send-email-jgross@suse.com>
Date: Tue, 19 Aug 2014 15:25:45 +0200
From: jgross@...e.com
To: stefan.bader@...onical.com, toshi.kani@...com,
linux-kernel@...r.kernel.org, xen-devel@...ts.xensource.com,
konrad.wilk@...cle.com, ville.syrjala@...ux.intel.com,
hpa@...or.com, x86@...nel.org
Cc: Juergen Gross <jgross@...e.com>
Subject: [PATCH RFC 3/3] Support Xen pv-domains using PAT
From: Juergen Gross <jgross@...e.com>
With the dynamical mapping between cache modes and pgprot values it is now
possible to use all cache modes via the Xen hypervisor PAT settings in a
pv domain.
All to be done is to read the PAT configuration MSR and set up the translation
tables accordingly.
Signed-off-by: Juergen Gross <jgross@...e.com>
---
arch/x86/xen/enlighten.c | 12 ++++++----
arch/x86/xen/mmu.c | 60 +++++++++++++++++-------------------------------
arch/x86/xen/xen-ops.h | 1 +
3 files changed, 30 insertions(+), 43 deletions(-)
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index c0cb11f..ef705a3 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1552,12 +1552,16 @@ asmlinkage __visible void __init xen_start_kernel(void)
xen_init_mmu_ops();
+ /*
+ * Modify the cache mode translation tables to match Xen's PAT
+ * configuration.
+ */
+
+ if (xen_init_cache_types())
+ __supported_pte_mask &= ~(_PAGE_PWT | _PAGE_PCD);
+
/* Prevent unwanted bits from being set in PTEs. */
__supported_pte_mask &= ~_PAGE_GLOBAL;
-#if 0
- if (!xen_initial_domain())
-#endif
- __supported_pte_mask &= ~(_PAGE_PWT | _PAGE_PCD);
__supported_pte_mask |= _PAGE_IOMAP;
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index e8a1201..49830c0 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -434,13 +434,7 @@ static pteval_t iomap_pte(pteval_t val)
__visible pteval_t xen_pte_val(pte_t pte)
{
pteval_t pteval = pte.pte;
-#if 0
- /* 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;
- }
-#endif
+
if (xen_initial_domain() && (pteval & _PAGE_IOMAP))
return pteval;
@@ -455,47 +449,35 @@ __visible 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- rsv UC-
- * 7 PAT PCD PWT UC rsv UC
+ * Xen's PAT setup is part of its ABI.
+ * We don't care what Linux wants to use, just fall back to the Xen PAT
+ * configuration. All we have to do in case of a Linux's PAT configuration
+ * is to overwrite the cache mode translation tables with the correct
+ * values for the Xen configuration.
*/
+int xen_init_cache_types(void)
+{
+ u64 pat;
+ int err;
+
+ err = rdmsrl_safe(MSR_IA32_CR_PAT, &pat);
+ if (!err)
+ pat_init_cache_modes(pat);
+ return err;
+}
+
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);
+ if (xen_init_cache_types())
+ /* Domain configured PAT, but we can't adapt to the changes */
+ BUG();
}
__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
- * _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;
- }
-#endif
+
/*
* 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 28c7e0b..da7e666 100644
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -34,6 +34,7 @@ extern unsigned long xen_max_p2m_pfn;
void xen_mm_pin_all(void);
void xen_mm_unpin_all(void);
void xen_set_pat(u64);
+int xen_init_cache_types(void);
char * __init xen_memory_setup(void);
char * xen_auto_xlated_memory_setup(void);
--
1.8.4.5
--
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