linux-kernel - Re: [PATCH 1/3] x86, mm: Include the entire kernel memory map in trampoline

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Date:	Wed, 03 Oct 2012 14:31:22 +0100
From:	"Jan Beulich" <jbeulich@...e.com>
To:	<matt@...sole-pimps.org>, <linux-kernel@...r.kernel.org>
Cc:	<matt.fleming@...el.com>, <mingo@...nel.org>, <x86@...nel.org>,
	<mjg@...hat.com>, <linux-efi@...r.kernel.org>, <hpa@...or.com>
Subject: Re: [PATCH 1/3] x86, mm: Include the entire kernel memory map
 in trampoline_pgd

>>> Matt Fleming <matt@...sole-pimps.org> 10/03/12 2:59 PM >>>
>+static int insert_identity_mapping(resource_size_t paddr, unsigned long vaddr,
>+                    unsigned long size)
>+{
>+    unsigned long end = vaddr + size;
>+    unsigned long next;
>+    pgd_t *vpgd, *ppgd;
>+
>+#ifdef CONFIG_X86_32
>+    ppgd = initial_page_table + pgd_index(paddr);
>+
>+    if (paddr >= PAGE_OFFSET || paddr + size > PAGE_OFFSET)
>+        return 1;
>+#else
>+    ppgd = __va(real_mode_header->trampoline_pgd) + pgd_index(paddr);

Missing equivalent code (to the 32-bit one above) here - after all, you're trying
to potentially insert a 52-bit physical address into 48-bit virtual space.

>+#endif
>+
>+    vpgd = pgd_offset_k(vaddr);
>+    do {
>+        next = pgd_addr_end(vaddr, end);
>+
>+        if (!pgd_present(*ppgd)) {
>+            pud_t *ppud = (pud_t *)get_zeroed_page(GFP_KERNEL);
>+            if (!ppud)
>+                return 1;
>+
>+            set_pgd(ppgd, __pgd(_KERNPG_TABLE | __pa(ppud)));
>+        }
>+
>+        if (ident_pud_range(paddr, vaddr, ppgd, vpgd, next))
>+            return 1;
>+    } while (ppgd++, vpgd++, vaddr = next, vaddr != end);
>+
>+    return 0;
>+}
>+
 >/*
>* Remap an arbitrary physical address space into the kernel virtual
>* address space. Needed when the kernel wants to access high addresses
>@@ -163,6 +258,10 @@ static void __iomem *__ioremap_caller(resource_size_t phys_addr,
>    ret_addr = (void __iomem *) (vaddr + offset);
>    mmiotrace_ioremap(unaligned_phys_addr, unaligned_size, ret_addr);
 >
>+    if (insert_identity_mapping(phys_addr, vaddr, size))
>+        printk(KERN_WARNING "ioremap: unable to map 0x%llx in identity pagetable\n",
>+                    (unsigned long long)phys_addr);

Isn't that going to trigger quite frequently on 32-bit kernels?

Jan

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