x86: kvm: Add MTRR support for kvm_get|put_msrs()

The MTRR state in KVM currently runs completely independent of the
QEMU state in CPUX86State.mtrr_*.  This means that on migration, the
target loses MTRR state from the source.  Generally that's ok though
because KVM ignores it and maps everything as write-back anyway.  The
exception to this rule is when we have an assigned device and an IOMMU
that doesn't promote NoSnoop transactions from that device to be cache
coherent.  In that case KVM trusts the guest mapping of memory as
configured in the MTRR.

This patch updates kvm_get|put_msrs() so that we retrieve the actual
vCPU MTRR settings and therefore keep CPUX86State synchronized for
migration.  kvm_put_msrs() is also used on vCPU reset and therefore
allows future modificaitons of MTRR state at reset to be realized.

Note that the entries array used by both functions was already
slightly undersized for holding every possible MSR, so this patch
increases it beyond the 28 new entries necessary for MTRR state.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Cc: qemu-stable@nongnu.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/target-i386/cpu.h b/target-i386/cpu.h
index d37d857d21..3460b12139 100644
--- a/target-i386/cpu.h
+++ b/target-i386/cpu.h
@@ -337,6 +337,8 @@
 #define MSR_MTRRphysBase(reg)           (0x200 + 2 * (reg))
 #define MSR_MTRRphysMask(reg)           (0x200 + 2 * (reg) + 1)
 
+#define MSR_MTRRphysIndex(addr)         ((((addr) & ~1u) - 0x200) / 2)
+
 #define MSR_MTRRfix64K_00000            0x250
 #define MSR_MTRRfix16K_80000            0x258
 #define MSR_MTRRfix16K_A0000            0x259