Revert "xen/x86: Workaround 64-bit hypervisor and 32-bit initial domain." and "xen/x86: Use memblock_reserve for sensitive areas."
This reverts commit806c312e50
and commit59b294403e
. And also documents setup.c and why we want to do it that way, which is that we tried to make the the memblock_reserve more selective so that it would be clear what region is reserved. Sadly we ran in the problem wherein on a 64-bit hypervisor with a 32-bit initial domain, the pt_base has the cr3 value which is not neccessarily where the pagetable starts! As Jan put it: " Actually, the adjustment turns out to be correct: The page tables for a 32-on-64 dom0 get allocated in the order "first L1", "first L2", "first L3", so the offset to the page table base is indeed 2. When reading xen/include/public/xen.h's comment very strictly, this is not a violation (since there nothing is said that the first thing in the page table space is pointed to by pt_base; I admit that this seems to be implied though, namely do I think that it is implied that the page table space is the range [pt_base, pt_base + nt_pt_frames), whereas that range here indeed is [pt_base - 2, pt_base - 2 + nt_pt_frames), which - without a priori knowledge - the kernel would have difficulty to figure out)." - so lets just fall back to the easy way and reserve the whole region. Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This commit is contained in:
parent
806c312e50
commit
51faaf2b0d
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@ -998,66 +998,7 @@ static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high)
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return ret;
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}
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/*
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* If the MFN is not in the m2p (provided to us by the hypervisor) this
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* function won't do anything. In practice this means that the XenBus
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* MFN won't be available for the initial domain. */
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static unsigned long __init xen_reserve_mfn(unsigned long mfn)
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{
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unsigned long pfn, end_pfn = 0;
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if (!mfn)
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return end_pfn;
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pfn = mfn_to_pfn(mfn);
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if (phys_to_machine_mapping_valid(pfn)) {
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end_pfn = PFN_PHYS(pfn) + PAGE_SIZE;
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memblock_reserve(PFN_PHYS(pfn), end_pfn);
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}
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return end_pfn;
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}
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static void __init xen_reserve_internals(void)
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{
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unsigned long size;
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unsigned long last_phys = 0;
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if (!xen_pv_domain())
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return;
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/* xen_start_info does not exist in the M2P, hence can't use
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* xen_reserve_mfn. */
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memblock_reserve(__pa(xen_start_info), PAGE_SIZE);
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last_phys = __pa(xen_start_info) + PAGE_SIZE;
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last_phys = max(xen_reserve_mfn(PFN_DOWN(xen_start_info->shared_info)), last_phys);
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last_phys = max(xen_reserve_mfn(xen_start_info->store_mfn), last_phys);
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if (!xen_initial_domain())
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last_phys = max(xen_reserve_mfn(xen_start_info->console.domU.mfn), last_phys);
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if (xen_feature(XENFEAT_auto_translated_physmap))
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return;
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/*
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* ALIGN up to compensate for the p2m_page pointing to an array that
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* can partially filled (look in xen_build_dynamic_phys_to_machine).
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*/
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size = PAGE_ALIGN(xen_start_info->nr_pages * sizeof(unsigned long));
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/* We could use xen_reserve_mfn here, but would end up looping quite
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* a lot (and call memblock_reserve for each PAGE), so lets just use
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* the easy way and reserve it wholesale. */
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memblock_reserve(__pa(xen_start_info->mfn_list), size);
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last_phys = max(__pa(xen_start_info->mfn_list) + size, last_phys);
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/* The pagetables are reserved in mmu.c */
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/* Under 64-bit hypervisor with a 32-bit domain, the hypervisor
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* offsets the pt_base by two pages. Hence the reservation that is done
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* in mmu.c misses two pages. We correct it here if we detect this. */
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if (last_phys < __pa(xen_start_info->pt_base))
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memblock_reserve(last_phys, __pa(xen_start_info->pt_base) - last_phys);
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}
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void xen_setup_shared_info(void)
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{
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if (!xen_feature(XENFEAT_auto_translated_physmap)) {
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@ -1421,7 +1362,6 @@ asmlinkage void __init xen_start_kernel(void)
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xen_raw_console_write("mapping kernel into physical memory\n");
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pgd = xen_setup_kernel_pagetable(pgd, xen_start_info->nr_pages);
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xen_reserve_internals();
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/* Allocate and initialize top and mid mfn levels for p2m structure */
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xen_build_mfn_list_list();
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@ -388,11 +388,6 @@ void __init xen_build_dynamic_phys_to_machine(void)
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}
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m2p_override_init();
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/* NOTE: We cannot call memblock_reserve here for the mfn_list as there
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* isn't enough pieces to make it work (for one - we are still using the
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* Xen provided pagetable). Do it later in xen_reserve_internals.
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*/
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}
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unsigned long get_phys_to_machine(unsigned long pfn)
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@ -424,6 +424,33 @@ char * __init xen_memory_setup(void)
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e820_add_region(ISA_START_ADDRESS, ISA_END_ADDRESS - ISA_START_ADDRESS,
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E820_RESERVED);
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/*
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* Reserve Xen bits:
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* - mfn_list
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* - xen_start_info
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* See comment above "struct start_info" in <xen/interface/xen.h>
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* We tried to make the the memblock_reserve more selective so
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* that it would be clear what region is reserved. Sadly we ran
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* in the problem wherein on a 64-bit hypervisor with a 32-bit
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* initial domain, the pt_base has the cr3 value which is not
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* neccessarily where the pagetable starts! As Jan put it: "
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* Actually, the adjustment turns out to be correct: The page
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* tables for a 32-on-64 dom0 get allocated in the order "first L1",
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* "first L2", "first L3", so the offset to the page table base is
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* indeed 2. When reading xen/include/public/xen.h's comment
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* very strictly, this is not a violation (since there nothing is said
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* that the first thing in the page table space is pointed to by
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* pt_base; I admit that this seems to be implied though, namely
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* do I think that it is implied that the page table space is the
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* range [pt_base, pt_base + nt_pt_frames), whereas that
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* range here indeed is [pt_base - 2, pt_base - 2 + nt_pt_frames),
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* which - without a priori knowledge - the kernel would have
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* difficulty to figure out)." - so lets just fall back to the
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* easy way and reserve the whole region.
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*/
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memblock_reserve(__pa(xen_start_info->mfn_list),
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xen_start_info->pt_base - xen_start_info->mfn_list);
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sanitize_e820_map(e820.map, ARRAY_SIZE(e820.map), &e820.nr_map);
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return "Xen";
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