Zide Chen c2283743f0 hv: basic MTRR virtualization ... Linux commit edfe63ec97ed ("x86/mtrr: Fix Xorg crashes in Qemu sessions") disables PAT feature if MTRR is not enabled. This patch does partial emulation of MTRR to prevent this from happening: enable fixed-range MTRRs and disable virable range MTRRs By default IA32_PAT MSR (SDM Vol3 11.12.4, Table 11-12) doesn't include 'WC' type. If MTRR is disabled from the guests, Linux doesn't allow writing IA32_PAT MSR so WC type can't be enabled. This creates some performance issues for certian applications that rely on WC memory type. Implementation summary: - Enable MTRR feature: MTRRdefType.E=1 - Enable fixed range MTRRs: MTRRCAP.fix=1, MTRRdefType.FE=1 - For simplicity, disable variable range MTRRs: MTRRCAP.vcnt=0. It's expected that this bit is honored by the guests and they won't change the guest memory type through variable MTRRs. Signed-off-by: bliu11 <baohong.liu@intel.com> Signed-off-by: Zide Chen <zide.chen@intel.com> Reviewed-by: Jason Chen CJ <jason.cj.chen@intel.com> Acked-by: Eddie Dong <eddie.dong@intel.com>		2018-06-08 12:06:15 +08:00
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x86	hv: basic MTRR virtualization	2018-06-08 12:06:15 +08:00