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c2283743f0
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>
52 lines
962 B
C
Executable File
52 lines
962 B
C
Executable File
/*
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* Copyright (C) <2018> Intel Corporation
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* SPDX-License-Identifier: BSD-3-Clause
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*/
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#ifndef MTRR_H
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#define MTRR_H
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#define FIXED_RANGE_MTRR_NUM 11
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#define MTRR_SUB_RANGE_NUM 8
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union mtrr_cap_reg {
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uint64_t value;
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struct {
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uint64_t vcnt:8;
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uint64_t fix:1;
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uint64_t res0:1;
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uint64_t wc:1;
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uint64_t res1:21;
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uint64_t res2:32;
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} bits;
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};
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union mtrr_def_type_reg {
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uint64_t value;
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struct {
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uint64_t type:8;
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uint64_t res0:2;
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uint64_t fixed_enable:1;
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uint64_t enable:1;
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uint64_t res1:20;
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uint64_t res2:32;
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} bits;
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};
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union mtrr_fixed_range_reg {
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uint64_t value;
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uint8_t type[MTRR_SUB_RANGE_NUM];
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};
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struct mtrr_state {
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union mtrr_cap_reg cap;
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union mtrr_def_type_reg def_type;
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union mtrr_fixed_range_reg fixed_range[FIXED_RANGE_MTRR_NUM];
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};
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void mtrr_wrmsr(struct vcpu *vcpu, uint32_t msr, uint64_t value);
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uint64_t mtrr_rdmsr(struct vcpu *vcpu, uint32_t msr);
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void init_mtrr(struct vcpu *vcpu);
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#endif /* MTRR_H */
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