0002-mttr.patch

   1 From fa7c4ebd5ae0c22f9908436303106a9ffcf0cf42 Mon Sep 17 00:00:00 2001
   2 From: Paolo Bonzini <pbonzini@redhat.com>
   3 Date: Mon, 14 Dec 2015 16:57:31 +0100
   4 Subject: KVM: MTRR: observe maxphyaddr from guest CPUID, not host
   5
   6 Conversion of MTRRs to ranges used the maxphyaddr from the boot CPU.
   7 This is wrong, because var_mtrr_range's mask variable then is discontiguous
   8 (like FF00FFFF000, where the first run of 0s corresponds to the bits
   9 between host and guest maxphyaddr).  Instead always set up the masks
  10 to be full 64-bit values---we know that the reserved bits at the top
  11 are zero, and we can restore them when reading the MSR.  This way
  12 var_mtrr_range gets a mask that just works.
  13
  14 Fixes: a13842dc668b40daef4327294a6d3bdc8bd30276
  15 Cc: qemu-stable@nongnu.org
  16 Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=107561
  17 Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
  18 ---
  19  arch/x86/kvm/mtrr.c | 9 +++++++--
  20  1 file changed, 7 insertions(+), 2 deletions(-)
  21
  22 diff --git a/arch/x86/kvm/mtrr.c b/arch/x86/kvm/mtrr.c
  23 index adc54e1..7747b6d 100644
  24 --- a/arch/x86/kvm/mtrr.c
  25 +++ b/arch/x86/kvm/mtrr.c
  26 @@ -300,7 +300,6 @@ static void var_mtrr_range(struct kvm_mtrr_range *range, u64 *start, u64 *end)
  27         *start = range->base & PAGE_MASK;
  28
  29         mask = range->mask & PAGE_MASK;
  30 -       mask |= ~0ULL << boot_cpu_data.x86_phys_bits;
  31
  32         /* This cannot overflow because writing to the reserved bits of
  33          * variable MTRRs causes a #GP.
  34 @@ -356,10 +355,14 @@ static void set_var_mtrr_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data)
  35         if (var_mtrr_range_is_valid(cur))
  36                 list_del(&mtrr_state->var_ranges[index].node);
  37
  38 +       /* Extend the mask with all 1 bits to the left, since those
  39 +        * bits must implicitly be 0.  The bits are then cleared
  40 +        * when reading them.
  41 +        */
  42         if (!is_mtrr_mask)
  43                 cur->base = data;
  44         else
  45 -               cur->mask = data;
  46 +               cur->mask = data | (-1LL << cpuid_maxphyaddr(vcpu));
  47
  48         /* add it to the list if it's enabled. */
  49         if (var_mtrr_range_is_valid(cur)) {
  50 @@ -426,6 +429,8 @@ int kvm_mtrr_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
  51                         *pdata = vcpu->arch.mtrr_state.var_ranges[index].base;
  52                 else
  53                         *pdata = vcpu->arch.mtrr_state.var_ranges[index].mask;
  54 +
  55 +               *pdata &= (1ULL << cpuid_maxphyaddr(vcpu)) - 1;
  56         }
  57
  58         return 0;
  59 --
  60 cgit v0.11.2
  61