2023-01-07 01:13:09

by Sean Christopherson

Subject: [PATCH 3/6] KVM: x86: Mark x2APIC DFR reg as non-existent for x2APIC

Mark APIC_DFR as being invalid/non-existent in x2APIC mode instead of
handling it as a one-off check in kvm_x2apic_msr_read(). This will allow
reusing "valid_reg_mask" to generate VMX's interception bitmaps for
x2APIC. Handling DFR in the common read path may also fix the Hyper-V
PV MSR interface, if that can coexist with x2APIC.

Signed-off-by: Sean Christopherson <[email protected]>
---
arch/x86/kvm/lapic.c | 11 ++++-------
1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index bf53e4752f30..c49b13418638 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1541,7 +1541,6 @@ static int kvm_lapic_reg_read(struct kvm_lapic *apic, u32 offset, int len,
APIC_REG_MASK(APIC_TASKPRI) |
APIC_REG_MASK(APIC_PROCPRI) |
APIC_REG_MASK(APIC_LDR) |
- APIC_REG_MASK(APIC_DFR) |
APIC_REG_MASK(APIC_SPIV) |
APIC_REGS_MASK(APIC_ISR, APIC_ISR_NR) |
APIC_REGS_MASK(APIC_TMR, APIC_ISR_NR) |
@@ -1562,12 +1561,13 @@ static int kvm_lapic_reg_read(struct kvm_lapic *apic, u32 offset, int len,
valid_reg_mask |= APIC_REG_MASK(APIC_LVTCMCI);

/*
- * ARBPRI and ICR2 are not valid in x2APIC mode. WARN if KVM reads ICR
- * in x2APIC mode as it's an 8-byte register in x2APIC and needs to be
- * manually handled by the caller.
+ * ARBPRI, DFR, and ICR2 are not valid in x2APIC mode. WARN if KVM
+ * reads ICR in x2APIC mode as it's an 8-byte register in x2APIC and
+ * needs to be manually handled by the caller.
*/
if (!apic_x2apic_mode(apic))
valid_reg_mask |= APIC_REG_MASK(APIC_ARBPRI) |
+ APIC_REG_MASK(APIC_DFR) |
APIC_REG_MASK(APIC_ICR2);
else
WARN_ON_ONCE(offset == APIC_ICR);
@@ -3141,9 +3141,6 @@ int kvm_x2apic_msr_read(struct kvm_vcpu *vcpu, u32 msr, u64 *data)
if (!lapic_in_kernel(vcpu) || !apic_x2apic_mode(apic))
return 1;

- if (reg == APIC_DFR)
- return 1;
-
return kvm_lapic_msr_read(apic, reg, data);
}

--
2.39.0.314.g84b9a713c41-goog

2023-01-08 16:58:42

by Maxim Levitsky

Subject: Re: [PATCH 3/6] KVM: x86: Mark x2APIC DFR reg as non-existent for x2APIC

On Sat, 2023-01-07 at 01:10 +0000, Sean Christopherson wrote:
> Mark APIC_DFR as being invalid/non-existent in x2APIC mode instead of
> handling it as a one-off check in kvm_x2apic_msr_read(). This will allow
> reusing "valid_reg_mask" to generate VMX's interception bitmaps for
> x2APIC. Handling DFR in the common read path may also fix the Hyper-V
> PV MSR interface, if that can coexist with x2APIC.
>
> Signed-off-by: Sean Christopherson <[email protected]>
> ---
> arch/x86/kvm/lapic.c | 11 ++++-------
> 1 file changed, 4 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index bf53e4752f30..c49b13418638 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -1541,7 +1541,6 @@ static int kvm_lapic_reg_read(struct kvm_lapic *apic, u32 offset, int len,
> APIC_REG_MASK(APIC_TASKPRI) |
> APIC_REG_MASK(APIC_PROCPRI) |
> APIC_REG_MASK(APIC_LDR) |
> - APIC_REG_MASK(APIC_DFR) |
> APIC_REG_MASK(APIC_SPIV) |
> APIC_REGS_MASK(APIC_ISR, APIC_ISR_NR) |
> APIC_REGS_MASK(APIC_TMR, APIC_ISR_NR) |
> @@ -1562,12 +1561,13 @@ static int kvm_lapic_reg_read(struct kvm_lapic *apic, u32 offset, int len,
> valid_reg_mask |= APIC_REG_MASK(APIC_LVTCMCI);
>
> /*
> - * ARBPRI and ICR2 are not valid in x2APIC mode. WARN if KVM reads ICR
> - * in x2APIC mode as it's an 8-byte register in x2APIC and needs to be
> - * manually handled by the caller.
> + * ARBPRI, DFR, and ICR2 are not valid in x2APIC mode. WARN if KVM
> + * reads ICR in x2APIC mode as it's an 8-byte register in x2APIC and
> + * needs to be manually handled by the caller.
> */
> if (!apic_x2apic_mode(apic))
> valid_reg_mask |= APIC_REG_MASK(APIC_ARBPRI) |
> + APIC_REG_MASK(APIC_DFR) |
> APIC_REG_MASK(APIC_ICR2);
> else
> WARN_ON_ONCE(offset == APIC_ICR);
> @@ -3141,9 +3141,6 @@ int kvm_x2apic_msr_read(struct kvm_vcpu *vcpu, u32 msr, u64 *data)
> if (!lapic_in_kernel(vcpu) || !apic_x2apic_mode(apic))
> return 1;
>
> - if (reg == APIC_DFR)
> - return 1;
> -
> return kvm_lapic_msr_read(apic, reg, data);
> }
>


Reviewed-by: Maxim Levitsky <[email protected]>
Best regards,
Maxim Levitsky