The patch below does not apply to the 6.1-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y git checkout FETCH_HEAD git cherry-pick -x 73b42dc69be8564d4951a14d00f827929fe5ef79 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2024100124-partly-overact-759b@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

73b42dc69be8 ("KVM: x86: Re-split x2APIC ICR into ICR+ICR2 for AMD (x2AVIC)") d33234342f8b ("KVM: x86: Move x2APIC ICR helper above kvm_apic_write_nodecode()") 71bf395a276f ("KVM: x86: Enforce x2APIC's must-be-zero reserved ICR bits") 4b7c3f6d04bd ("KVM: x86: Make x2APIC ID 100% readonly") c7d4c5f01961 ("KVM: x86: Drop unused check_apicv_inhibit_reasons() callback definition") 5f18c642ff7e ("KVM: VMX: Move out vmx_x86_ops to 'main.c' to dispatch VMX and TDX") 0ec3d6d1f169 ("KVM: x86: Fully defer to vendor code to decide how to force immediate exit") bf1a49436ea3 ("KVM: x86: Move handling of is_guest_mode() into fastpath exit handlers") 11776aa0cfa7 ("KVM: VMX: Handle forced exit due to preemption timer in fastpath") e6b5d16bbd2d ("KVM: VMX: Re-enter guest in fastpath for "spurious" preemption timer exits") 9c9025ea003a ("KVM: x86: Plumb "force_immediate_exit" into kvm_entry() tracepoint") 8ecb10bcbfa3 ("Merge tag 'kvm-x86-lam-6.8' of https://github.com/kvm-x86/linux into HEAD")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 73b42dc69be8564d4951a14d00f827929fe5ef79 Mon Sep 17 00:00:00 2001 From: Sean Christopherson seanjc@google.com Date: Fri, 19 Jul 2024 16:51:00 -0700 Subject: [PATCH] KVM: x86: Re-split x2APIC ICR into ICR+ICR2 for AMD (x2AVIC)

Re-introduce the "split" x2APIC ICR storage that KVM used prior to Intel's IPI virtualization support, but only for AMD. While not stated anywhere in the APM, despite stating the ICR is a single 64-bit register, AMD CPUs store the 64-bit ICR as two separate 32-bit values in ICR and ICR2. When IPI virtualization (IPIv on Intel, all AVIC flavors on AMD) is enabled, KVM needs to match CPU behavior as some ICR ICR writes will be handled by the CPU, not by KVM.

Add a kvm_x86_ops knob to control the underlying format used by the CPU to store the x2APIC ICR, and tune it to AMD vs. Intel regardless of whether or not x2AVIC is enabled. If KVM is handling all ICR writes, the storage format for x2APIC mode doesn't matter, and having the behavior follow AMD versus Intel will provide better test coverage and ease debugging.

Fixes: 4d1d7942e36a ("KVM: SVM: Introduce logic to (de)activate x2AVIC mode") Cc: stable@vger.kernel.org Cc: Maxim Levitsky mlevitsk@redhat.com Cc: Suravee Suthikulpanit suravee.suthikulpanit@amd.com Link: https://lore.kernel.org/r/20240719235107.3023592-4-seanjc@google.com Signed-off-by: Sean Christopherson seanjc@google.com

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 95396e4cb3da..f9dfb2d62053 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1727,6 +1727,8 @@ struct kvm_x86_ops { void (*enable_nmi_window)(struct kvm_vcpu *vcpu); void (*enable_irq_window)(struct kvm_vcpu *vcpu); void (*update_cr8_intercept)(struct kvm_vcpu *vcpu, int tpr, int irr); + + const bool x2apic_icr_is_split; const unsigned long required_apicv_inhibits; bool allow_apicv_in_x2apic_without_x2apic_virtualization; void (*refresh_apicv_exec_ctrl)(struct kvm_vcpu *vcpu); diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index 63be07d7c782..c7180cb5f464 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -2471,11 +2471,25 @@ int kvm_x2apic_icr_write(struct kvm_lapic *apic, u64 data) data &= ~APIC_ICR_BUSY;

kvm_apic_send_ipi(apic, (u32)data, (u32)(data >> 32)); - kvm_lapic_set_reg64(apic, APIC_ICR, data); + if (kvm_x86_ops.x2apic_icr_is_split) { + kvm_lapic_set_reg(apic, APIC_ICR, data); + kvm_lapic_set_reg(apic, APIC_ICR2, data >> 32); + } else { + kvm_lapic_set_reg64(apic, APIC_ICR, data); + } trace_kvm_apic_write(APIC_ICR, data); return 0; }

+static u64 kvm_x2apic_icr_read(struct kvm_lapic *apic) +{ + if (kvm_x86_ops.x2apic_icr_is_split) + return (u64)kvm_lapic_get_reg(apic, APIC_ICR) | + (u64)kvm_lapic_get_reg(apic, APIC_ICR2) << 32; + + return kvm_lapic_get_reg64(apic, APIC_ICR); +} + /* emulate APIC access in a trap manner */ void kvm_apic_write_nodecode(struct kvm_vcpu *vcpu, u32 offset) { @@ -2493,7 +2507,7 @@ void kvm_apic_write_nodecode(struct kvm_vcpu *vcpu, u32 offset) * maybe-unecessary write, and both are in the noise anyways. */ if (apic_x2apic_mode(apic) && offset == APIC_ICR) - WARN_ON_ONCE(kvm_x2apic_icr_write(apic, kvm_lapic_get_reg64(apic, APIC_ICR))); + WARN_ON_ONCE(kvm_x2apic_icr_write(apic, kvm_x2apic_icr_read(apic))); else kvm_lapic_reg_write(apic, offset, kvm_lapic_get_reg(apic, offset)); } @@ -3013,18 +3027,22 @@ static int kvm_apic_state_fixup(struct kvm_vcpu *vcpu,

/* * In x2APIC mode, the LDR is fixed and based on the id. And - * ICR is internally a single 64-bit register, but needs to be - * split to ICR+ICR2 in userspace for backwards compatibility. + * if the ICR is _not_ split, ICR is internally a single 64-bit + * register, but needs to be split to ICR+ICR2 in userspace for + * backwards compatibility. */ - if (set) { + if (set) *ldr = kvm_apic_calc_x2apic_ldr(x2apic_id);

- icr = __kvm_lapic_get_reg(s->regs, APIC_ICR) | - (u64)__kvm_lapic_get_reg(s->regs, APIC_ICR2) << 32; - __kvm_lapic_set_reg64(s->regs, APIC_ICR, icr); - } else { - icr = __kvm_lapic_get_reg64(s->regs, APIC_ICR); - __kvm_lapic_set_reg(s->regs, APIC_ICR2, icr >> 32); + if (!kvm_x86_ops.x2apic_icr_is_split) { + if (set) { + icr = __kvm_lapic_get_reg(s->regs, APIC_ICR) | + (u64)__kvm_lapic_get_reg(s->regs, APIC_ICR2) << 32; + __kvm_lapic_set_reg64(s->regs, APIC_ICR, icr); + } else { + icr = __kvm_lapic_get_reg64(s->regs, APIC_ICR); + __kvm_lapic_set_reg(s->regs, APIC_ICR2, icr >> 32); + } } }

@@ -3222,7 +3240,7 @@ static int kvm_lapic_msr_read(struct kvm_lapic *apic, u32 reg, u64 *data) u32 low;

if (reg == APIC_ICR) { - *data = kvm_lapic_get_reg64(apic, APIC_ICR); + *data = kvm_x2apic_icr_read(apic); return 0; }

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index d8cfe8f23327..eb3de01602b9 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -5053,6 +5053,8 @@ static struct kvm_x86_ops svm_x86_ops __initdata = { .enable_nmi_window = svm_enable_nmi_window, .enable_irq_window = svm_enable_irq_window, .update_cr8_intercept = svm_update_cr8_intercept, + + .x2apic_icr_is_split = true, .set_virtual_apic_mode = avic_refresh_virtual_apic_mode, .refresh_apicv_exec_ctrl = avic_refresh_apicv_exec_ctrl, .apicv_post_state_restore = avic_apicv_post_state_restore, diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c index 4f6023a0deb3..0a094ebad4b1 100644 --- a/arch/x86/kvm/vmx/main.c +++ b/arch/x86/kvm/vmx/main.c @@ -89,6 +89,8 @@ struct kvm_x86_ops vt_x86_ops __initdata = { .enable_nmi_window = vmx_enable_nmi_window, .enable_irq_window = vmx_enable_irq_window, .update_cr8_intercept = vmx_update_cr8_intercept, + + .x2apic_icr_is_split = false, .set_virtual_apic_mode = vmx_set_virtual_apic_mode, .set_apic_access_page_addr = vmx_set_apic_access_page_addr, .refresh_apicv_exec_ctrl = vmx_refresh_apicv_exec_ctrl,