Re: [PATCH v2 1/2] KVM: VMX: Cleanup VMX basic information defines and usages
From: Xin Li
Date: Fri Oct 27 2023 - 14:00:08 EST
On 10/27/2023 2:29 AM, Huang, Kai wrote:
+/* VMX_BASIC bits and bitmasks */
+#define VMX_BASIC_32BIT_PHYS_ADDR_ONLY BIT_ULL(48)
+#define VMX_BASIC_MEM_TYPE_WB 6LLU
Strictly speaking, VMX_BASIC_MEM_TYPE_MB isn't any bit definition or bitmasks of
VMX_BASIC MSR. So perhaps better to put it somewhere under separately.
Actually you reminded me that the memory type WB is architectural on
x86, but I can't find it defined in a common x86 header.
We also have:
#define VMX_EPTP_MT_WB 0x6ull
which is simply redundant if we have a common definition MEMTYPE_WB.
+#define VMX_BASIC_INOUT BIT_ULL(54)
+
+/* VMX_MISC bits and bitmasks */
Your next patch is to "Cleanup VMX misc information defines and usages", so I
guess it's better to move any VMX_MISC related change to that patch.
ah, you're right.
#define VMX_MISC_PREEMPTION_TIMER_RATE_MASK 0x0000001f
#define VMX_MISC_SAVE_EFER_LMA 0x00000020
#define VMX_MISC_ACTIVITY_HLT 0x00000040
@@ -143,6 +149,16 @@ static inline u32 vmx_basic_vmcs_size(u64 vmx_basic)
return (vmx_basic & GENMASK_ULL(44, 32)) >> 32;
}
+static inline u32 vmx_basic_vmcs_basic_cap(u64 vmx_basic)
+{
+ return (vmx_basic & GENMASK_ULL(63, 45)) >> 32;
+}
+
+static inline u32 vmx_basic_vmcs_mem_type(u64 vmx_basic)
+{
+ return (vmx_basic & GENMASK_ULL(53, 50)) >> 50;
+}
+
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/nested.c b/arch/x86/kvm/vmx/nested.c
index 4ba46e1b29d2..274d480d9071 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -1201,23 +1201,34 @@ static bool is_bitwise_subset(u64 superset, u64 subset, u64 mask)
return (superset | subset) == superset;
}
+#define VMX_BASIC_VMCS_SIZE_SHIFT 32
+#define VMX_BASIC_DUAL_MONITOR_TREATMENT BIT_ULL(49)
+#define VMX_BASIC_MEM_TYPE_SHIFT 50
+#define VMX_BASIC_TRUE_CTLS BIT_ULL(55)
If I am reading correctly, the two "*_SHIFT" above are not used? The above
vmx_basic_vmcs_mem_type() and vmx_basic_vmcs_basic_cap() use hard-coded values
directly.
The 2 shift macros are needed in arch/x86/kvm/vmx/nested.c.
And How about moving all these bit/mask definitions to <asm/vmx.h> above?
It's better they stay together for better readability.
Sean kind of prefers to keep the macros close to code that uses it,
unless they are used somewhere else.
+
+#define VMX_BASIC_FEATURES_MASK \
+ (VMX_BASIC_DUAL_MONITOR_TREATMENT | \
+ VMX_BASIC_INOUT | \
+ VMX_BASIC_TRUE_CTLS)
+
+#define VMX_BASIC_RESERVED_BITS \
+ (GENMASK_ULL(63, 56) | GENMASK_ULL(47, 45) | BIT_ULL(31))
+
Also move these to <asm/vmx.h>?
static int vmx_restore_vmx_basic(struct vcpu_vmx *vmx, u64 data)
{
- const u64 feature_and_reserved =
- /* feature (except bit 48; see below) */
- BIT_ULL(49) | BIT_ULL(54) | BIT_ULL(55) |
- /* reserved */
- BIT_ULL(31) | GENMASK_ULL(47, 45) | GENMASK_ULL(63, 56);
u64 vmx_basic = vmcs_config.nested.basic;
- if (!is_bitwise_subset(vmx_basic, data, feature_and_reserved))
+ static_assert(!(VMX_BASIC_FEATURES_MASK & VMX_BASIC_RESERVED_BITS));
+
+ if (!is_bitwise_subset(vmx_basic, data,
+ VMX_BASIC_FEATURES_MASK | VMX_BASIC_RESERVED_BITS))
return -EINVAL;
/*
* KVM does not emulate a version of VMX that constrains physical
* addresses of VMX structures (e.g. VMCS) to 32-bits.
*/
- if (data & BIT_ULL(48))
+ if (data & VMX_BASIC_32BIT_PHYS_ADDR_ONLY)
return -EINVAL;
if (vmx_basic_vmcs_revision_id(vmx_basic) !=
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 4c3a70f26b42..b68d54f6e9f8 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2568,14 +2568,13 @@ 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 misc_msr;
+ u64 vmx_basic;
int i;
/*
@@ -2693,28 +2692,26 @@ 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, vmx_basic);
/* IA-32 SDM Vol 3B: VMCS size is never greater than 4kB. */
- if ((vmx_msr_high & 0x1fff) > PAGE_SIZE)
+ if ((vmx_basic_vmcs_size(vmx_basic) > 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 (vmx_basic & VMX_BASIC_32BIT_PHYS_ADDR_ONLY)
return -EIO;
#endif
/* Require Write-Back (WB) memory type for VMCS accesses. */
- if (((vmx_msr_high >> 18) & 15) != 6)
+ if (vmx_basic_vmcs_mem_type(vmx_basic) != 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(vmx_basic);
+ vmcs_conf->basic_cap = vmx_basic_vmcs_basic_cap(vmx_basic);
- vmcs_conf->revision_id = vmx_msr_low;
+ vmcs_conf->revision_id = vmx_basic_vmcs_revision_id(vmx_basic);
I actually tried to do similar thing before, and Sean gave me below advice:
Rather than do all of these weird dances, what about saving the
full/raw
MSR in the config, and then using the helpers to extract info as
needed?
https://lkml.kernel.org/kvm/20230330092149.101047-1-kai.huang@xxxxxxxxx/T/#m4879a3c7e66ede7bfa568a25aea4f6e3778e6e34
I agreed, but I has been too lazy to do this, sorry :-)
So maybe we should still go with this approach?
Yes, this looks more consistent.
vmcs_conf->pin_based_exec_ctrl = _pin_based_exec_control;
vmcs_conf->cpu_based_exec_ctrl = _cpu_based_exec_control;
@@ -2722,7 +2719,8 @@ static int setup_vmcs_config(struct vmcs_config *vmcs_conf,
vmcs_conf->cpu_based_3rd_exec_ctrl = _cpu_based_3rd_exec_control;
vmcs_conf->vmexit_ctrl = _vmexit_control;
vmcs_conf->vmentry_ctrl = _vmentry_control;
- vmcs_conf->misc = misc_msr;
+
+ rdmsrl(MSR_IA32_VMX_MISC, vmcs_conf->misc);
Better to move VMX_MISC code to next patch I suppose.
I view it a bit different, but maybe your suggestion is better.
Thanks!
Xin