Re: [PATCH v6 10/34] x86, x86/mm, x86/xen, olpc: Use __va() against just the physical address in cr3

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On 6/7/2017 5:06 PM, Boris Ostrovsky wrote:
On 06/07/2017 03:14 PM, Tom Lendacky wrote:
The cr3 register entry can contain the SME encryption bit that indicates
the PGD is encrypted.  The encryption bit should not be used when creating
a virtual address for the PGD table.

Create a new function, read_cr3_pa(), that will extract the physical
address from the cr3 register. This function is then used where a virtual
address of the PGD needs to be created/used from the cr3 register.

Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
---
  arch/x86/include/asm/special_insns.h |    9 +++++++++
  arch/x86/kernel/head64.c             |    2 +-
  arch/x86/mm/fault.c                  |   10 +++++-----
  arch/x86/mm/ioremap.c                |    2 +-
  arch/x86/platform/olpc/olpc-xo1-pm.c |    2 +-
  arch/x86/power/hibernate_64.c        |    2 +-
  arch/x86/xen/mmu_pv.c                |    6 +++---
  7 files changed, 21 insertions(+), 12 deletions(-)


...

diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c
index 1f386d7..2dc5243 100644
--- a/arch/x86/xen/mmu_pv.c
+++ b/arch/x86/xen/mmu_pv.c
@@ -2022,7 +2022,7 @@ static phys_addr_t __init xen_early_virt_to_phys(unsigned long vaddr)
  	pmd_t pmd;
  	pte_t pte;
- pa = read_cr3();
+	pa = read_cr3_pa();
  	pgd = native_make_pgd(xen_read_phys_ulong(pa + pgd_index(vaddr) *
  						       sizeof(pgd)));
  	if (!pgd_present(pgd))
@@ -2102,7 +2102,7 @@ void __init xen_relocate_p2m(void)
  	pt_phys = pmd_phys + PFN_PHYS(n_pmd);
  	p2m_pfn = PFN_DOWN(pt_phys) + n_pt;
- pgd = __va(read_cr3());
+	pgd = __va(read_cr3_pa());
  	new_p2m = (unsigned long *)(2 * PGDIR_SIZE);
  	idx_p4d = 0;
  	save_pud = n_pud;
@@ -2209,7 +2209,7 @@ static void __init xen_write_cr3_init(unsigned long cr3)
  {
  	unsigned long pfn = PFN_DOWN(__pa(swapper_pg_dir));
- BUG_ON(read_cr3() != __pa(initial_page_table));
+	BUG_ON(read_cr3_pa() != __pa(initial_page_table));
  	BUG_ON(cr3 != __pa(swapper_pg_dir));
/*


(Please copy Xen maintainers when modifying xen-related files.)

Sorry about that, missed adding the Xen maintainers when I added this
change.


Given that page tables for Xen PV guests are controlled by the
hypervisor I don't think this change (although harmless) is necessary.

I can back this change out if the Xen maintainers think that's best.

What may be needed is making sure X86_FEATURE_SME is not set for PV guests.

And that may be something that Xen will need to control through either
CPUID or MSR support for the PV guests.

Thanks,
Tom


-boris

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