linux-kernel - [PATCH] KVM: VMX: Get rid of hard-coded value around IA32_VMX

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Date:   Thu, 30 Mar 2023 22:21:49 +1300
From:   Kai Huang <kai.huang@...el.com>
To:     kvm@...r.kernel.org
Cc:     seanjc@...gle.com, pbonzini@...hat.com,
        linux-kernel@...r.kernel.org, Kai Huang <kai.huang@...el.com>
Subject: [PATCH] KVM: VMX: Get rid of hard-coded value around IA32_VMX_BASIC

Currently, setup_vmcs_config() uses hard-coded values when performing
sanity check on the value of IA32_VMX_BASIC MSR and setting up the three
members of 'vmcs_config': size, revison_id and basic_cap.  However, the
kernel actually already has macro definitions for those relevant bits in
asm/msr-index.h and functions to get revision_id and size in asm/vmx.h.

Add the missing helper function to get the basic_cap, and use those
macros and helper functions in setup_vmcs_config() to get rid of those
hard-coded values.

No functional change intended.

Signed-off-by: Kai Huang <kai.huang@...el.com>
---
 arch/x86/include/asm/vmx.h |  5 +++++
 arch/x86/kvm/vmx/vmx.c     | 17 +++++++++--------
 2 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
index 498dc600bd5c..2b488895fe0e 100644
--- a/arch/x86/include/asm/vmx.h
+++ b/arch/x86/include/asm/vmx.h
@@ -141,6 +141,11 @@ static inline u32 vmx_basic_vmcs_size(u64 vmx_basic)
 	return (vmx_basic & GENMASK_ULL(44, 32)) >> 32;
 }
 
+static inline u32 vmx_basic_cap(u64 vmx_basic)
+{
+	return (vmx_basic & ~GENMASK_ULL(44, 32)) >> 32;
+}
+
 static inline int vmx_misc_preemption_timer_rate(u64 vmx_misc)
 {
 	return vmx_misc & VMX_MISC_PREEMPTION_TIMER_RATE_MASK;
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index c3ef74562158..8f4982ec3c8c 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2597,13 +2597,13 @@ static u64 adjust_vmx_controls64(u64 ctl_opt, u32 msr)
 static int setup_vmcs_config(struct vmcs_config *vmcs_conf,
 			     struct vmx_capability *vmx_cap)
 {
-	u32 vmx_msr_low, vmx_msr_high;
 	u32 _pin_based_exec_control = 0;
 	u32 _cpu_based_exec_control = 0;
 	u32 _cpu_based_2nd_exec_control = 0;
 	u64 _cpu_based_3rd_exec_control = 0;
 	u32 _vmexit_control = 0;
 	u32 _vmentry_control = 0;
+	u64 basic_msr;
 	u64 misc_msr;
 	int i;
 
@@ -2722,28 +2722,29 @@ static int setup_vmcs_config(struct vmcs_config *vmcs_conf,
 		_vmexit_control &= ~x_ctrl;
 	}
 
-	rdmsr(MSR_IA32_VMX_BASIC, vmx_msr_low, vmx_msr_high);
+	rdmsrl(MSR_IA32_VMX_BASIC, basic_msr);
 
 	/* IA-32 SDM Vol 3B: VMCS size is never greater than 4kB. */
-	if ((vmx_msr_high & 0x1fff) > PAGE_SIZE)
+	if (vmx_basic_vmcs_size(basic_msr) > PAGE_SIZE)
 		return -EIO;
 
 #ifdef CONFIG_X86_64
 	/* IA-32 SDM Vol 3B: 64-bit CPUs always have VMX_BASIC_MSR[48]==0. */
-	if (vmx_msr_high & (1u<<16))
+	if (basic_msr & VMX_BASIC_64)
 		return -EIO;
 #endif
 
 	/* Require Write-Back (WB) memory type for VMCS accesses. */
-	if (((vmx_msr_high >> 18) & 15) != 6)
+	if (((basic_msr & VMX_BASIC_MEM_TYPE_MASK) >> VMX_BASIC_MEM_TYPE_SHIFT)
+			!= VMX_BASIC_MEM_TYPE_WB)
 		return -EIO;
 
 	rdmsrl(MSR_IA32_VMX_MISC, misc_msr);
 
-	vmcs_conf->size = vmx_msr_high & 0x1fff;
-	vmcs_conf->basic_cap = vmx_msr_high & ~0x1fff;
+	vmcs_conf->size = vmx_basic_vmcs_size(basic_msr);
+	vmcs_conf->basic_cap = vmx_basic_cap(basic_msr);
 
-	vmcs_conf->revision_id = vmx_msr_low;
+	vmcs_conf->revision_id = vmx_basic_vmcs_revision_id(basic_msr);
 
 	vmcs_conf->pin_based_exec_ctrl = _pin_based_exec_control;
 	vmcs_conf->cpu_based_exec_ctrl = _cpu_based_exec_control;

base-commit: 99b30869804ea59d9596cdbefa5cc3aabd588521
-- 
2.39.2