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Date: Mon, 19 Feb 2024 14:33:49 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Dongli Zhang <dongli.zhang@...cle.com>
Cc: kvm@...r.kernel.org, pbonzini@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] KVM: VMX: simplify MSR interception enable/disable
On Fri, Feb 16, 2024, Dongli Zhang wrote:
> ---
> arch/x86/kvm/vmx/vmx.c | 55 +++++++++++++++++++++---------------------
> 1 file changed, 28 insertions(+), 27 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 5a866d3c2bc8..76dff0e7d8bd 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -669,14 +669,18 @@ static int possible_passthrough_msr_slot(u32 msr)
> return -ENOENT;
> }
>
> -static bool is_valid_passthrough_msr(u32 msr)
> +#define VMX_POSSIBLE_PASSTHROUGH 1
> +#define VMX_OTHER_PASSTHROUGH 2
> +/*
> + * Vefify if the msr is the passthrough MSRs.
> + * Return the index in *possible_idx if it is a possible passthrough MSR.
> + */
> +static int validate_passthrough_msr(u32 msr, int *possible_idx)
There's no need for a custom tri-state return value or an out-param, just return
the slot/-ENOENT. Not fully tested yet, but this should do the trick.
From: Sean Christopherson <seanjc@...gle.com>
Date: Mon, 19 Feb 2024 07:58:10 -0800
Subject: [PATCH] KVM: VMX: Combine "check" and "get" APIs for passthrough MSR
lookups
Combine possible_passthrough_msr_slot() and is_valid_passthrough_msr()
into a single function, vmx_get_passthrough_msr_slot(), and have the
combined helper return the slot on success, using a negative value to
indiciate "failure".
Combining the operations avoids iterating over the array of passthrough
MSRs twice for relevant MSRs.
Suggested-by: Dongli Zhang <dongli.zhang@...cle.com>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
arch/x86/kvm/vmx/vmx.c | 63 +++++++++++++++++-------------------------
1 file changed, 25 insertions(+), 38 deletions(-)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 014cf47dc66b..969fd3aa0da3 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -658,25 +658,14 @@ static inline bool cpu_need_virtualize_apic_accesses(struct kvm_vcpu *vcpu)
return flexpriority_enabled && lapic_in_kernel(vcpu);
}
-static int possible_passthrough_msr_slot(u32 msr)
+static int vmx_get_passthrough_msr_slot(u32 msr)
{
- u32 i;
-
- for (i = 0; i < ARRAY_SIZE(vmx_possible_passthrough_msrs); i++)
- if (vmx_possible_passthrough_msrs[i] == msr)
- return i;
-
- return -ENOENT;
-}
-
-static bool is_valid_passthrough_msr(u32 msr)
-{
- bool r;
+ int i;
switch (msr) {
case 0x800 ... 0x8ff:
/* x2APIC MSRs. These are handled in vmx_update_msr_bitmap_x2apic() */
- return true;
+ return -ENOENT;
case MSR_IA32_RTIT_STATUS:
case MSR_IA32_RTIT_OUTPUT_BASE:
case MSR_IA32_RTIT_OUTPUT_MASK:
@@ -691,14 +680,16 @@ static bool is_valid_passthrough_msr(u32 msr)
case MSR_LBR_CORE_FROM ... MSR_LBR_CORE_FROM + 8:
case MSR_LBR_CORE_TO ... MSR_LBR_CORE_TO + 8:
/* LBR MSRs. These are handled in vmx_update_intercept_for_lbr_msrs() */
- return true;
+ return -ENOENT;
}
- r = possible_passthrough_msr_slot(msr) != -ENOENT;
-
- WARN(!r, "Invalid MSR %x, please adapt vmx_possible_passthrough_msrs[]", msr);
+ for (i = 0; i < ARRAY_SIZE(vmx_possible_passthrough_msrs); i++) {
+ if (vmx_possible_passthrough_msrs[i] == msr)
+ return i;
+ }
- return r;
+ WARN(1, "Invalid MSR %x, please adapt vmx_possible_passthrough_msrs[]", msr);
+ return -ENOENT;
}
struct vmx_uret_msr *vmx_find_uret_msr(struct vcpu_vmx *vmx, u32 msr)
@@ -3954,6 +3945,7 @@ void vmx_disable_intercept_for_msr(struct kvm_vcpu *vcpu, u32 msr, int type)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
unsigned long *msr_bitmap = vmx->vmcs01.msr_bitmap;
+ int idx;
if (!cpu_has_vmx_msr_bitmap())
return;
@@ -3963,16 +3955,13 @@ void vmx_disable_intercept_for_msr(struct kvm_vcpu *vcpu, u32 msr, int type)
/*
* Mark the desired intercept state in shadow bitmap, this is needed
* for resync when the MSR filters change.
- */
- if (is_valid_passthrough_msr(msr)) {
- int idx = possible_passthrough_msr_slot(msr);
-
- if (idx != -ENOENT) {
- if (type & MSR_TYPE_R)
- clear_bit(idx, vmx->shadow_msr_intercept.read);
- if (type & MSR_TYPE_W)
- clear_bit(idx, vmx->shadow_msr_intercept.write);
- }
+ */
+ idx = vmx_get_passthrough_msr_slot(msr);
+ if (idx >= 0) {
+ if (type & MSR_TYPE_R)
+ clear_bit(idx, vmx->shadow_msr_intercept.read);
+ if (type & MSR_TYPE_W)
+ clear_bit(idx, vmx->shadow_msr_intercept.write);
}
if ((type & MSR_TYPE_R) &&
@@ -3998,6 +3987,7 @@ void vmx_enable_intercept_for_msr(struct kvm_vcpu *vcpu, u32 msr, int type)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
unsigned long *msr_bitmap = vmx->vmcs01.msr_bitmap;
+ int idx;
if (!cpu_has_vmx_msr_bitmap())
return;
@@ -4008,15 +3998,12 @@ void vmx_enable_intercept_for_msr(struct kvm_vcpu *vcpu, u32 msr, int type)
* Mark the desired intercept state in shadow bitmap, this is needed
* for resync when the MSR filter changes.
*/
- if (is_valid_passthrough_msr(msr)) {
- int idx = possible_passthrough_msr_slot(msr);
-
- if (idx != -ENOENT) {
- if (type & MSR_TYPE_R)
- set_bit(idx, vmx->shadow_msr_intercept.read);
- if (type & MSR_TYPE_W)
- set_bit(idx, vmx->shadow_msr_intercept.write);
- }
+ idx = vmx_get_passthrough_msr_slot(msr);
+ if (idx >= 0) {
+ if (type & MSR_TYPE_R)
+ set_bit(idx, vmx->shadow_msr_intercept.read);
+ if (type & MSR_TYPE_W)
+ set_bit(idx, vmx->shadow_msr_intercept.write);
}
if (type & MSR_TYPE_R)
base-commit: 342c6dfc2a0ae893394a6f894acd1d1728c009f2
--
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