linux-kernel - [PATCH] xen: support 52 bit physical addresses in pv guests

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Date:   Thu, 21 Sep 2017 10:01:38 +0200
From:   Juergen Gross <jgross@...e.com>
To:     linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org
Cc:     boris.ostrovsky@...cle.com, kirill.shutemov@...ux.intel.com,
        Juergen Gross <jgross@...e.com>
Subject: [PATCH] xen: support 52 bit physical addresses in pv guests

Physical addresses on processors supporting 5 level paging can be up to
52 bits wide. For a Xen pv guest running on such a machine those
physical addresses have to be supported in order to be able to use any
memory on the machine even if the guest itself does not support 5 level
paging.

So when reading/writing a MFN from/to a pte don't use the kernel's
PTE_PFN_MASK but a new XEN_PTE_MFN_MASK allowing full 40 bit wide MFNs.

Signed-off-by: Juergen Gross <jgross@...e.com>
---
 arch/x86/include/asm/xen/page.h | 11 ++++++++++-
 arch/x86/xen/mmu_pv.c           |  4 ++--
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
index 07b6531813c4..bcb8b193c8d1 100644
--- a/arch/x86/include/asm/xen/page.h
+++ b/arch/x86/include/asm/xen/page.h
@@ -26,6 +26,15 @@ typedef struct xpaddr {
 	phys_addr_t paddr;
 } xpaddr_t;
 
+#ifdef CONFIG_X86_64
+#define XEN_PHYSICAL_MASK	((1UL << 52) - 1)
+#else
+#define XEN_PHYSICAL_MASK	__PHYSICAL_MASK
+#endif
+
+#define XEN_PTE_MFN_MASK	((pteval_t)(((signed long)PAGE_MASK) & \
+					    XEN_PHYSICAL_MASK))
+
 #define XMADDR(x)	((xmaddr_t) { .maddr = (x) })
 #define XPADDR(x)	((xpaddr_t) { .paddr = (x) })
 
@@ -277,7 +286,7 @@ static inline unsigned long bfn_to_local_pfn(unsigned long mfn)
 
 static inline unsigned long pte_mfn(pte_t pte)
 {
-	return (pte.pte & PTE_PFN_MASK) >> PAGE_SHIFT;
+	return (pte.pte & XEN_PTE_MFN_MASK) >> PAGE_SHIFT;
 }
 
 static inline pte_t mfn_pte(unsigned long page_nr, pgprot_t pgprot)
diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c
index 509f560bd0c6..958d36d776d9 100644
--- a/arch/x86/xen/mmu_pv.c
+++ b/arch/x86/xen/mmu_pv.c
@@ -315,7 +315,7 @@ void xen_ptep_modify_prot_commit(struct mm_struct *mm, unsigned long addr,
 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 mfn = (val & XEN_PTE_MFN_MASK) >> PAGE_SHIFT;
 		unsigned long pfn = mfn_to_pfn(mfn);
 
 		pteval_t flags = val & PTE_FLAGS_MASK;
@@ -1740,7 +1740,7 @@ static unsigned long __init m2p(phys_addr_t maddr)
 {
 	phys_addr_t paddr;
 
-	maddr &= PTE_PFN_MASK;
+	maddr &= XEN_PTE_MFN_MASK;
 	paddr = mfn_to_pfn(maddr >> PAGE_SHIFT) << PAGE_SHIFT;
 
 	return paddr;
-- 
2.12.3